We think men particularly like FastDay and intermittent fasting methods such as 5:2 because:
Most of the time we are free to eat normally, and fasting does not take over our life in the way that a ‘diet’ can. You can love food and still succeed.
It works well. In fact, there is some evidence that fasting may be particularly well suited to the male physiology.
The rules of 5:2 fasting are clear, specific and waffle-free. On the two fasting days there is a clear rule, and we know what to do.
It appeals to the hunter-gatherer in us. Many men come to like the idea that they are hungry today (as if we hadn’t caught anything)…but that we will eat again tomorrow.
FastDay helps you track your progress, and compare how you are doing with other people. Is it unfair to say that men like to compete with each other….and love to have data? We know we do.
FastDay is all about helping you succeed in reaching your goals and then staying there so you can live a healthier life and still love food.
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Side-effects of losing a lot of weight
Wednesday 7th May 2014
Some of the problems that members of our FastDay community mention are due to weight loss rather than from fasting itself. For example:
Saggy skin if you lose a lot of weight.
Increased hair loss, particularly if you lose weight rapidly.
Change in menstrual cycle in women, which is likely due to changes in oestrogen levels associated with adipose tissue.
Flabby, loose skin
If you have a lot of weight you need to lose, unless you are still quite young, it is likely that your skin will take on a flabby appearance, seeming to be too big for your body. You may develop drooping skin over the abdomen forming an ‘apron’. Rapid weight loss (and 0.5kg per week is rapid even if it seems slow to you) often leads to this unsightly problem, which for people who have lost particularly large amounts of weight, can be rather depressing.
This loose skin is partly due to the skin not being able to shrink at the same speed as the reducing fat stores. It is also partly because the fat stored under the skin is not packed in as tightly as it was and becomes jelly-like in consistency with a higher water content. Finally, in severe obesity, the accumulating fat under the skin damages its structure so that when the fat is lost, the skin cannot return to its former size and elasticity. This occurs especially in the abdomen resulting in the ‘apron’ effect.
As we age, we our skin becomes less elastic in any case, and so losing weight in later life is more likely to result in loose skin.
There is good news though. Over time the loose skin will slowly decrease as your body decreases the amount of skin you have (as opposed to shrinking the existing skin), the water content will decrease and the fat stores become more firm. Although it is hard to predict how much the skin will shrink – skin elasticity varies from person to person and certain things can make worsen the skin’s stretchiness, such as exposure to sun, heat and cigarette smoking.
Regarding the tendency for the fat stored under the skin to be soft and flabby, firming up the muscles underneath through toning exercises can help its appearance. Skin is attached to your muscles by fibres that tighten up with increased muscular exercise, thus pulling skin in tighter to the muscle. Increased muscle mass will fill the space left by weight loss. Also as you lose more weight, some more of the fat stored under the skin will disappear and the flabbiness will decrease. So, further weight loss may not make the situation worse.
There are many products available which claim to help reduce loose skin, but as yet, none have lived up to their marketing claims. Good skin care, preventing skin from becoming dry, and use of creams to minimize development of skin problems in skin folds is certainly sensible.
In severe cases of excess skin, it is possible to have plastic surgery to remove the excess skin. Most surgeons will advise patients to wait for at least two years after reaching a stable weight to see how much the skin will shrink of its own accord.
If you are concerned about loose skin, there are various things you can try:
Working on toning your body through pilates or similar exercises
Moisturize your skin regularly
Support the loose skin by wearing close fitting underwear so as to prevent the weight of the skin from further stretching it and to provide a contouring effect
Some feel that cold water on the skin, or body brushing or other methods to improve the circulation in the skin can help to tone it up
Lose weight slowly to allow time for your body to adjust the fit of your skin to your changing size
If you are extremely unhappy with your loose skin, visit your doctor to discuss possible surgical options.
Hair loss
Rapid weight loss can be accompanied by an increase in how fast you shed hair. You might notice more hair on your hairbrush or accumulating in the shower plug hole and wonder if you are losing more hair than usual. Some of our forum members have had this happen.
When you lose weight rapidly it is because you are cutting your calorie intake by quite a large amount and this is likely to be accompanied by a cut in the amount of nutrients you are eating. There are several nutrients needed for healthy hair growth which may become deficient on a low calorie diet. With the fast diet (5:2 or 4:3) the days of normal eating should ensure you are not becoming deficient in nutrients, but if you find you are also eating a lot less on the non-fast days and you notice increased hair loss, you may need to make efforts to increase the amount of the following nutrients in your diet:
Biotin and other B vitamins (found in chocolate, dairy, eggs, fish and shellfish, nuts and seeds, whole grains and yeast)
Zinc (found in dairy, legumes/pulses, eggs, meats, nuts and seeds and whole grains)
Copper (found in fish and shellfish, dark leafy greens, nuts and seeds and whole grains)
Iron (found in eggs, fish and shellfish, legumes/pulses, liver, and meats).
Change in menstrual cycle
Losing weight reduces the size of your fat stores (adipose tissue). As oestrogen is stored and also manufactured in adipose tissue,1 changes in the amount of adipose tissue may cause a change in a woman’s menstrual cycle. Members of our FastDay forum have reported periods coming sooner than expected, break-through bleeding when taking the contraceptive pill, longer or heavier periods but also many members have noticed improvements in pre-menstrual symptoms, period pains and lighter, shorter periods.
Weight loss and fasting also affects levels of many other hormones, including the appetite hormone, leptin, which itself can affect menstrual cycles via its action in the part of the brain, the hypothalamus, that orchestrates the menstrual cycle. Thus many hormone changes occur with weight loss which can disrupt the menstrual cycle.
As you become used to fasting, things should settle down and overall your oestrogen levels will decrease.2 In fact, the oestrogen stored in your adipose tissue can increase your risk of breast and other hormone-related cancers, so losing weight will help reduce this risk by reducing the amount of stored oestrogen.
Studies examining the effects of fasting on reproductive hormones have found that despite some changes in the timing of hormone secretion there is no change in reproductive function3 so you need not worry that fasting will affect your ability to conceive. In fact, if you are overweight, losing weight will likely improve your ability to conceive.
If you suffer from polycystic ovary syndrome, fasting and weight loss may be beneficial through its effects on insulin resistance as well as reproductive hormone levels.
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How can I improve my sleep on fast days?
The mild and beneficial stress of fasting tends to make our brains more alert (presumably so that our ancient ancestors would be alert to any food possibilities!) but this can sometimes spill over into when we go to bed, making us more wakeful than usual.
Like most of the ‘side-effects’ of fasting, the insomnia of fast days is worse with the first few fasts and improves as we get used to fasting. For a few, however, insomnia remains a problem.
As we age, we tend not to sleep so deeply as when we were young, and for women going through the menopause, sleep can be even more disturbed. Both ageing and the menopause are also often accompanied by weight gain, so unfortunately, many people looking to lose weight through fasting are also struggling with insomnia. In fact, poor sleep has been well established as being connected with weight gain.
If you are struggling with sleep problems, whether on fast days or on non-fast days as well here are some tips that may help.
Save some calories for a snack before bed
Ideally we should avoid eating just before bedtime, but a low-carbohydrate, high protein/high fat snack before bed can help with sleep. This might be a milky drink or a cube of cheese. Try saving a few calories from your fast-day allowance for a late snack, many people on the FastDay forum have found that this can help sleep on a fast day.
Ensure you have good sleep hygiene
Sleep hygiene is all about making sure we prepare properly for sleep and includes such things as:1
Don’t do screen-based activities close to bedtime (or in bed). This not only means turning off the television but also avoiding using your smart phone, tablet or similar devices. The light from their screens is blue-ish and blue light interferes with production of the sleep hormone, melatonin, which should rise in the evening in response to the fading daylight.
Keep the bedroom dark and cool.
Do not use the bedroom for work, hobbies or anything that involves being mentally active.
Do not exercise close to bedtime.
Do not sleep late in the morning to make up for lost sleep at night. Set a period of time when you ‘should’ be sleeping (say 11pm to 7am). Whether or not you manage to sleep well, get up at 7 am and don’t go to bed before 11 pm. This helps to keep your body clock and sleep hormones working properly.
Get outside especially during the morning hours
Low light levels from being indoors interferes with the natural rhythm of hormones that control sleep. Even if you think you are in a brightly lit room, it will never be close to the amount of light outdoors. As we age, this problem worsens due to changes in the structure of our eyes. Spending time outdoors, especially in the morning, can help with sleep.1,2
Secondly, being outdoors enables our bodies to make vitamin D. Many people in the higher latitudes, especially those who are overweight, are deficient in vitamin D. Even in the summer, our efforts to avoid sunburn – covering up and using sunscreens – prevent our bodies from manufacturing enough vitamin D. Vitamin D is not only important in bone health but is also involved in a myriad of other bodily processes, one of which is getting a good night’s sleep.
Lastly, studies show that people who spend time out of doors in the early morning tend to weigh less.3
Supplements
Many herbal supplements are marketed as being beneficial for improving sleep. Unfortunately, there is very little scientific evidence to back up their claims. Worse, many herbal supplements can have dangerous side-effects, in particular Jamaican dogwood, kava kava, alcohol, and L-tryptophan.4
Valerian root extract has shown some limited effectiveness in scientific studies.4
Magnesium plays a key role in sleep and magnesium deficiency is common. Taking a supplement that provides 500mg of elemental magnesium has been shown to improve sleep in elderly people.5,6 The tablets need to be taken shortly before bedtime and the type of magnesium tablets is important. Some forms of magnesium are better absorbed than others with the poorly absorbed forms, such as magnesium oxide or magnesium hydroxide, tend to have a laxative effect while the better absorbed forms, such as magnesium citrate are more effective for insomnia.
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How can I prevent constipation after fast days?
Probably the commonest side-effect of having days with only minimal calorie intake, such as on the intermittent fasting patterns of 5:2, 4:3 and ADF is constipation. If you find that you do not need to strain despite having fewer bowel movements, this is not a problem – apart from a possible temporary increase in weight as the food collects. If, however, you develop true constipation with discomfort and straining while you are intermittent fasting, the tips that follow may be helpful.
The traditional advice from doctors and health professionals is to increase your fibre consumption, drink more water and take some exercise.
Fibre should be ‘soluble’ fibre such as is found in oats, chia seeds, flaxseed, pulses (legumes), psyllium husk and certain fruits and vegetables (notably passion fruit, prunes, figs, avocados and brussels sprouts).
Water: if you are dehydrated, this can worsen constipation, but if you are adequately hydrated drinking more will not necessarily help. It is important to drink plenty on fast days as you are not obtaining any water from your foods as you do on non-fast days.
Exercise such as jogging, brisk walking, aerobics etc shakes up your intestines a little and helps things move along.
However, if you already have a high-fibre diet, drink plenty of water and exercise, but are still having problems with constipation after fasting days, further increasing fibre, water and exercise may not be any help.1 What else can help with constipation?
Probiotics: supplementation with certain probiotics, especially the bacterium called Bifidobacterium has been shown to help constipation caused by low calorie dieting and Lactobacillus may also be helpful.1 Weight loss can affect the normal balance of gut bacteria, which may be why probiotics can help.
Natural live yoghurt, which normally contains Lactobacillus and, if possible, with added Bifidobacterium, together with an oat-based cereal, such as muesli or granola topped with figs or prunes, could bring together the elements of probiotics and soluble fibre in one healthy breakfast!
Magnesium has a laxative effect (and there is some speculation that the studies showing that increased water consumption helps with constipation might actually have achieved their improvements from the magnesium content in hard water). Magnesium is a mineral that is often deficient in our diets, possibly due to modern farming practices. Absorption of vitamin D and calcium both need adequate magnesium in the body. Magnesium supplementation can help with constipation and may also help with poor sleep, hypertension, and muscular aches and pains. The recommended dose of magnesium is 400mg per day of elemental magnesium. Some forms of magnesium are better absorbed than others with the poorly absorbed forms, such as magnesium oxide or magnesium hydroxide, having a bigger laxative effect while the better absorbed forms, such as magnesium citrate being more effective for insomnia. If you decide to supplement your diet with magnesium tablets, it is wise to build up your dose slowly as the laxative effect can be quite dramatic!
Coffee is well-known to stimulate the intestines and trigger bowel movement.
Laxatives are not recommended unless prescribed by your doctor. They can actually worsen constipation.
If these measures do not help your constipation problems you should probably visit your doctor to check that there is no other reason for the constipation.
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Intermittent fasting for people with thyroid disorders
Having a thyroid disorder often causes weight problems, as weight goes on easily but is very hard to reduce. This can be frustrating, and also a cause of further health problems. The good news is that many thyroid sufferers in the FastDay community have found that intermittent fasting has been the best way they have found to lose weight.
The thyroid gland is a key player in how much energy your body uses (its metabolic rate).1 An under-active thyroid can lower the amount of energy you burn in a day by a significant amount, while treatment for an over-active thyroid can have the same effect. It is no wonder that weight problems are so common.
Tips on how to use intermittent fasting to best effect with thyroid disorders
Our FastDay community has many people with thyroid problems – whether due to an under-active thyroid, having had their thyroid removed or being on treatment for an over-active thyroid.
Do not fast for too long a period
For people with thyroid problems a slow down in metabolic rate that occurs after some hours of fasting1,2 may be particularly undesirable. To prevent this, do not fast for more than 24 hours without some food, possibly less. More frequent, shorter, fasts are probably the better choice. So you might prefer to use a 4:3 or ADF schedule rather than 5:2 or perhaps a daily eating window approach will suit you best. You might find that 4:3 with a higher calorie allowance (say 1000 calories on a fast day) will be more effective than standard 5:2 on only 500/600 calories although the actual reduction in weekly calorie intake would be around the same. It make take a bit of experimenting for you to find out what works best for you.
Our bodies have evolved to be active and feed during the daytime and to rest at night time. The production of thyroid hormones is arranged to fit with this natural pattern. When your thyroid is not working as well as it should, keeping your eating times to daylight hours may help it to function most efficiently. Thus, on a fast day, aim to have your meal(s) when it is light outside.
Eat some carbohydrates but not too much
Carbohydrates can stimulate thyroid function but can also worsen weight gain, so a balanced approach is best. Although at FastDay we usually suggest you avoid all carbohydrate on a fast day, if you have a thyroid disorder, you should include some carbohydrate. This does not need to be a large amount, perhaps between 80g and 150g of net carbs. Of course, this would apply to non-fast days as well.
Do not over-exercise
Intense exercise can result in a decrease in thyroid function (presumably the body’s way of trying to compensate for the high energy use during exercise) especially if repeated daily.3 Leave a day between each bout of strenuous exercise to allow your body to recover.
Get your medications checked regularly as you lose weight
Your thyroid medications need to be adjusted as you lose weight not only because the correct dose depends on your weight but also because losing weight and intermittent fasting itself may affect the way your thyroid functions. Some people with an under-active thyroid have found that their medications could be reduced and so have some people with an over-active thyroid. So it is hard to predict how your body will respond.
More information for the scientifically inclined
How the thyroid and thyroid hormones work
Your thyroid gland, which is situated in the lower front part of your neck, produces hormones that play a role in a variety of functions throughout the body, and impact many other hormones outside the thyroid. The two main states of dysfunction seen in thyroid conditions are called hyperthyroidism (too much hormone) and hypothyroidism (too little).
Thyroid function starts in the brain where the pituitary gland releases a hormone called thyroid stimulating hormone (TSH). TSH stimulates the thyroid to produce its hormones. These are called T4 (thyroxine), T3 (triiodothyronine), T2 and T1. The most important hormones are T4 and T3. T4 is a kind of ‘storage’ hormone, whose main function is to convert to the active thyroid hormone T3. People who have an under-active thyroid or who have had their thyroid removed have to take thyroxine (T4). Without this conversion of T4 to T3, cells have too little T3 to maintain normal metabolism. T3, therefore, is the important thyroid hormone. For the most part, T4 is metabolically inactive.The conversion of T4 to T3 occurs in the tissues where T3 exerts its effects. T3 affects every cell in your body and ensures your body temperature remains stable and your cells are functioning correctly. The situation is complicated by the existence of another molecule termed reverse-T3, which is also made from T4 but reverse-T3 does not stimulate metabolism.
Under normal conditions, the body’s cells continually convert about 40% of T4 to T3 while the remaining 60% of T4 is converted to reverse-T3. Hour-by-hour, conversion of T4 continues with slight shifts in the percentage of T4 converted to T3 and reverse-T3. Usually, the body eliminates reverse-T3 rapidly, so that it has little effect. If levels of reverse-T3 are very high, however, it may be that it can inhibit the effect of T3 but this is uncertain.
Thus the final effect on the metabolism will depend on:
How much TSH is produced by the pituitary
How much T4 and T3 is produced by the thyroid
How much T4 is converted to T3 and how much to reverse-T3 in the tissues.
Thyroid function testing
The first place doctors look to find out whether a person has a thyroid problem is to measure the amount of TSH in the blood: high levels of TSH show that the brain is trying to get the thyroid to produce more hormones and so suggests that the thyroid is not responding as it should. However, if TSH is normal that does not mean that all is well. It could be that you do not have enough T4 or that there is not enough T4 being converted to T3. Thus to get a better picture of thyroid function, it is important to test levels of T4, T3 and, ideally, reverse-T3 as well. However, large amounts of the T4 and T3 produced by the body become bound to proteins in the blood where they cannot exert any effects on metabolism. Thus it is important that the values of ‘free T4’ and ‘free T3’ are tested not ‘total T4’ and ‘total T3’.
If you have an under-active thyroid and are taking thyroxine but continue to have symptoms of an under-active thyroid – tiredness, feeling the cold, weight gain and the inability to lose weight, hair loss, loss of libido etc., it could be that the thyroxine is not being converted to an adequate amount of T3.
During fasting, disease, or any other stress, the conversion of T4 to reverse-T3 increases. At these times, conversion of T4 to T3 decreases about 50%, and conversion of T4 to reverse-T3 increases about 50% resulting in a slowing of the metabolic rate.
In people with normal thyroid function, studies have found that fasting causes an initial increase in T4 levels followed by a gradual fall in the ratio of T3 to T4 during the first 24 hours of the fast.2 TSH levels fall steadily,1 showing that thyroid function increases at the start of the fast but later decreases. An increase in reverse-T3 to T3 ratio is also seen.1,2 Indeed, any period of calorie restriction causes a slow down in thyroid function.4 When food is re-introduced after a fast, there is a rapid increase in thyroid function even when the amount of food is fairly small.1,5
There have been few studies of fasting in people with thyroid disorders. One found that people with an under-active thyroid tended to respond similarly to those with normal thyroid function.6
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Fasting with type 2 diabetes
Thursday 1st May 2014
Intermittent fasting can be an effective way of losing weight and helping you manage type 2 diabetes. Many members of our community are now free of diabetes medications, or have seen significant improvements in their condition.
How does it work? Fasting will help you lose weight, and lowers insulin resistance. This means it tackles the root cause of type 2 diabetes.
A word of warning: if you need insulin to control your diabetes you should not do intermittent fasting unless you have discussed your proposed fasting plan with your doctor – and unless you are very well trained in adjusting your insulin doses (for example by the DAPHNE programme)
What should I know about fasting with type 2 diabetes?
Start slowly
If you have type 2 diabetes you may find the first fasts particularly difficult as your high circulating insulin levels will make it hard for your body to switch into fat burning. Thus, it may be wise to start fasting gently by allowing yourself more calories in a day, or by only doing short fasts to begin with. As your body adapts to fasting, you can lengthen your fasts.
Experiment with different methods of fasting
You may need to experiment with different methods of intermittent fasting to see which works best for you. Different people respond differently to fasting (and differently to different forms of fasting).
For example, many members of our community with type 2 diabetes tell us that a daily eating window approach works better for them than 5:2, as it combines weight loss with relatively stable blood glucose levels.
To help keep your blood glucose under control you should limit all carbohydrates on both fast days and non-fast days. It is best to aim to keep your net carbohydrate intake below 100g per day, and these should come from foods with a low glycaemic index and glycaemic load.
In the past, you may have been told that you should eat plenty of complex carbohydrates for your diabetes. Unfortunately, science has now shown that this is bad advice. Eating carbohydrates increases your blood glucose, creating a need for insulin – and type 2 diabetes develops when your body is not creating enough insulin to cope. In short, eating carbs puts more pressure on your already-overloaded system.
Find recipe ideas for low carbohydrate meals and snacks.
To learn more about the scientific evidence for low carb eating with type 2 diabetes, see the section below on ‘More information for the scientifically inclined.’
Go low-carb when you break your fast
It is especially important to choose lower carbohydrate foods as the first thing you eat when you break a fast. This might be your daily breakfast, or the first food you eat after a fast day.
In the mornings, you may find that your blood glucose tends to be higher (the ‘dawn phenomenon’) due to sugar production by the liver overnight. In this case, a small low-carbohydrate snack, such as a handful of nuts can help to turn off the release of sugar by the liver. Some people find that the morning rise in blood glucose is worse if the previous day has been one in which they ate a lot of carbohydrate.
It is also possible that your body is slower than normal to respond to glucose from your food immediately after a fast day. This might result in a higher peak of blood glucose than normal. To keep this peak to a minimum it is wise to choose lower GI foods – which generally means lower carb foods.
Be ready to adjust the dose of medications
The first adjustment you need to make to your medications will probably be on fast days. Your reduced food intake when you are fasting will lead to lower blood glucose levels and hence to a need to adjust your medication. (Note: monitor blood glucose regularly and remember that metformin doses do not need adjustment: see below)
After you have had some success and lost weight you may also find that you will need to adjust your medication on non-fast days. Again, you need to monitor blood glucose carefully so as to adjust your doses appropriately.
FastDay has many members with type 2 diabetes who have found that they have been able to withdraw some or all of their diabetes medications permanently. We think this is great, and we are really proud of them!
Remember you should always monitor your blood glucose carefully and that if you wish to discontinue a medication you should always consult with your healthcare team before making changes. (Note: It is recommended that, if you are taking metformin, you continue to do so – and this should be the last of your medications to be dropped because it works to reduce insulin resistance and so is complementary to fasting and low carbohydrate eating.)
Hypoglycaemic episodes
Some diabetes drugs, especially the sulphonylureas (e.g., glipizide, gliclazide, glibenclamide, glyburide, glibornuride, gliquidone, glisoxepide, glyclopyramide and glimepiride) can cause hypoglycaemic episodes (low blood sugar) as your insulin sensitivity improves during a fast, because they stimulate too much insulin release from the pancreas than is needed once your insulin sensitivity has improved. If you experience a hypoglycaemic episode, do treat it as normal with some carbohydrate, but also try to reduce your dose of medications rather than increase the carbohydrate content of your food on fasting days.
Exercise
Adding exercise to your day, particularly while you are still fasting, will further help to control your blood sugar and to reverse your diabetes. This is because exercise, like low carbohydrate eating and intermittent fasting, improves insulin sensitivity.
To improve your type 2 diabetes we recommend you should do all three of:
1. Intermittent fasting
2. Lower carb eating
3. Take some exercise
Intermittent fasting and type 2 diabetes research results
Studies have shown that:
Women with type 2 diabetes who fasted for 3 days showed lower blood glucose and enhanced insulin sensitivity.1
People with type 2 diabetes who extended their normal overnight fast from 12 to 18 hours showed a 23% fall in blood glucose concentrations between 12 and 18 hours of fasting.2
Men with type 2 diabetes who fasted for 24 hours showed a fall in blood glucose and insulin levels.3
Studies on fasting during the holy month of Ramadan have confirmed that fasting is safe for people with diabetes.4
Scientific evidence for the benefits of combining low carbohydrate eating with intermittent fasting
A Swedish study5 examined the effects of three different diets on blood glucose and insulin in 19 subjects with type 2 diabetes. The calorie content in all the diets was the same.
The first diet was a conventional low-fat diet (45–56% of energy from carbohydrates, which represents over 200g of carbohydrates per day); the second was an intermittent fasting regimen in which people skipped breakfast and then followed a Mediterranean diet with moderate carbohydrates (32–35% of energy, which represents around 150–175g of carbohydrates per day), they had a large lunch which had the same number of calories as breakfast and lunch combined in the other diets; the third was a low carbohydrate diet (16–24% of energy, which represents about 80-120g per day). All participants tried all three diets, one diet each day in randomized order. See the chart below.
The effects of diet on blood sugar levels throughout the day
Red line shows the low fat diet Green line shows intermittent fasting Blue line shows low carbohydrate diet
The low-fat diet (that most people with type 2 diabetes are still advised by their doctors to follow) actually produced the worst blood sugar levels throughout the day, with high peaks and overall higher levels of blood glucose than the other diets. The medium carbohydrate diet combined with skipping breakfast led to excellent blood sugar levels in the morning, and while the big lunch did cause a spike in blood sugar levels, these were no worse than those after the small lunch on the low-fat diet. The low carbohydrate diet gave much smaller peaks in blood sugar after breakfast and lunch resulting in the lowest average blood sugar levels throughout the day.
The changes in insulin levels showed a similar pattern as shown in the chart below (figure 2). With skipping breakfast on the intermittent fasting plus medium carbohydrate regimen, insulin levels were kept very low for an extended time, but it is important to note that the big lunch caused a large increase in insulin, showing the importance of breaking the fast with low carbohydrate food.
The changes in insulin levels throughout the day
Red line shows the low fat diet Green line shows intermittent fasting Blue line shows low carbohydrate diet
Unfortunately, the researchers did not examine what happens when intermittent fasting is combined with a low carbohydrate diet, but it is probable that one would gain the benefits of both.
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What should be my goal weight?
Wednesday 30th April 2014
Setting a weight loss target can be surprisingly difficult. Here are some questions you should answer when thinking about an appropriate target:
What is a healthy weight for you?
What do you think is your ideal weight?
How will you look at this weight?
How will you feel at this weight?
Can you reach this weight and maintain it without excessive fasting?
Would a target weight range be more appropriate than a fixed weight?
This topic has been much discussed at the FastDay forum. Here are some of our thoughts on setting a target weight.
What is a healthy weight for you?
Body Mass Index (BMI)
To get an idea of what your healthy weight might be, you could start by calculating what you will weigh when your body mass index (BMI) is under 25. To do this easily, take your height in metres and multiply it by itself and then by 25 (e.g. 1.64 x 1.64 x 25 = 67.24). This gives you the weight in kg that is the point at which you are considered overweight. If you then multiply by 18.5 instead of 25 you get the point at which you are considered underweight. You will notice that the range of healthy weights (BMI 18 to 25) is rather large (in the case of a woman of height 1.64m, she could weigh anything between 49.75kg and 67.24kg, which is an enormous range). Where should you aim to be within this range? Statistically, a BMI of 22 seems to be associated with the best life expectancy, but statistics deals with averaging out huge populations and so a target of a BMI of 22 may not be the best for you! You need to consider your frame size, your age, how fit you are and your waist size when thinking about what your healthy weight will be.
BMI is used by doctors everywhere to assess whether someone is carrying a healthy amount of body fat, but it has many shortcomings:
1) BMI does not account for frame size. If you have large/heavy bones or small/light bones the BMI figures will not be right for you. To get an idea of your frame size, measure around your wrist at the narrowest point. Then use the table below to determine whether you have a small, medium or large frame. Choose the row that corresponds to your height and then look across to see what your wrist measurement would be for different frame sizes.
Height
You have a small body frame if your wrist measures:
You have a medium body frame if your wrist measures:
You have a large body frame if your wrist measures:
Women 5’2″ (157cm) and below
less than 5.5 inches (139 mm)
5.5–5.75″ (139–146 mm)
more than 5.75″ (146 mm)
Women between 5’2″ and 5’5″ (157–165 cm)
less than 6″ (152 mm)
6–6.25″ (152–158 mm)
more than 6.25″ (158 mm)
Women taller than 5’5″ (165 cm)
less than 6.25″ (158 mm)
6.25–6.5″ (158–165 mm)
more than 6.5″ (165 mm)
Men taller than 5’5″ (165 cm)
5.5–6.5″ (139–165 mm)
6.5–7.5″ (165–190 mm)
more than 7.5″ (190 mm)
If you have a large frame you can add 10% to the healthy BMI range or if a small frame you need to subtract 10% (e.g., if you are 1.64m tall with a large frame, then 1.64 x 1.64 x 25 = 67.24 + 6.72 = 73.96, so 73.96kg represents the top of healthy BMI range for you).
2) If you are very fit you will have more muscle than the average person so, again, your BMI will not reflect how much fat you are carrying and a high BMI may represent a healthy weight for you.
3) Your healthy weight increases slightly as you age. There is some scientific evidence that for people aged over 65 years it is better to have a slightly higher weight (BMI 24 to 27).
Perhaps then, BMI is not such a suitable guide to your healthy weight.
Waist size
As waist size is actually a much better measure of your health (as discussed in measuring success), why not set a target waist measurement rather than a target weight? Your target should be to get your waist to measure less than half of your height.
Body fat
If you have a way of measuring your body fat percentage (many modern weighing scales do this or you can buy a body fat monitor), then you could even set a body fat target. After all, whenever we discuss what we should weigh, we are really talking about how much fat we should be carrying (and how much muscle). The table below gives some ideas as to potential body fat targets. Again, in older individuals the target should be set a little higher.
Description
Women
Men
Essential fat
10–13%
2–5%
Athletes
14–20%
6–13%
Fitness
21–24%
14–17%
Average
25–31%
18–24%
Obese
32%+
25%+
What do you think is your ideal weight?
As mentioned above, the healthy weight range is rather large so when picking your target weight you will need to think about what would be your ideal weight. Your ideal weight should not be something unattainable though. You could use a weight that you have been before when you thought you looked and felt your best, perhaps in your early adulthood. The benefit of using this weight as your target is that it is far more personalized than using BMI, waist size or body fat. If you have been that weight before, then most likely you can be that weight again.
How will you look and feel at that weight?
It is important to be realistic when setting a target weight. It may be that if you were to attain what you think is your ‘ideal’ weight you would actually look too gaunt, you might feel too bony. If as you approach your target your friends and family start to mention how thin you are looking and asking if you are going to stop losing weight, do not dismiss their concerns. Ask them to take photos of you that show how you really look. You might be surprised that you look rather different in the photos than you do when you look at yourself in the mirror!
Can you reach this weight without excessive fasting?
It may be that your body has other ideas about what is your ideal weight and that to keep on losing weight you need to add more fast days or restrict your eating in some other way which you find is not sustainable. It is far more important to lose some weight and keep it off than to reach your target through heroic measures which you cannot sustain and then end up putting the weight back on. Remember that this is a Way of Eating for life, not just until you reach a certain target. Always ask yourself “can I eat this way for the rest of my life?” whenever you are considering adding an extra fast day or some other change. If you find you have to accept a higher target weight than you hoped for, above all remember that you have improved your health enormously by losing weight and that by continuing to fast you are continuing to bring health benefits.
Would a target range be more appropriate than a fixed weight?
Our bodies vary in weight by quite a large amount day to day. The amount of water and fat in our bodies changes daily. Thus, when one day you weigh yourself and you find you have reached your target (well done you!), the next time you weigh it is likely you will be heavier or lighter. Do not panic! If you weigh 500g more than last week, it is probably just that today you have more water in your body. If you weigh 500g less you may be a little dehydrated. For the sake of your sanity, it is best to have in mind an upper and a lower limit on your weight rather than a fixed target. So, you may say that your target is 60kg, but you should rather say “I aim not to weigh more than 61 kg or less than 59kg”.
If you’re thinking about entering maintenance: congratulations! You should celebrate your success in getting to this stage. Now it’s time to move on to create long-term success using fasting as your permanent Way of Eating. At FastDay we focus on the long-term view, not the short-term, quick fix approach weight loss that will not result in a permanent health improvement.
Maintaining a new lower weight is certainly not easy. Of the millions of people who lose weight each year, only a small proportion manage to keep the weight off. The numbers quoted vary from 2%1 to 20%,2 most of which depends on your definition of success. However you calculate the numbers, though, it is clear that there is a lot more to successfully maintaining a lower weight than just reaching your goal weight. One of the reasons weight maintenance is so hard is that after losing weight our bodies try to regain the fat stores just in case another famine is around the corner! Learn about what happens to our metabolism when we lose weight
With intermittent fasting, you have the tools to keep the weight off:
Fasting combats many of the body’s mechanisms to try to trick you into regaining the weight
Intermittent fasting is very flexible allowing you to adjust your maintenance plan as you go along
Intermittent fasting means not having to be on a diet for the rest of your life.
Have confidence that your Way of Eating will give you control over your weight now and in the future!
FastDay’s top 5 tips for successful maintenance
1. Work out your plan for the future
Fasting for maintenance usually means a different pattern: perhaps fasting just one day a week (6:1) or increasing your calorie allowance on a 5:2 pattern; moving to an eating window approach. You may need to experiment for a while to work out what suits you best.
Decide on an acceptable weight range beyond which you need to take action. We suggest you allow yourself at least 1kg either side of your goal weight to allow for normal daily weight variations. Remember that your daily calorie needs will change if you do more/less exercise and with changes in circumstances, you may need to adjust your fasting to compensate.
Have an action plan in place for when you see an increase/decrease in weight that you cannot put down to normal daily weight variations – perhaps you will fast for an extra day or avoid sugar for a week – until your weight returns to target.
Respond to quickly when your weight strays out of your acceptable range – the longer you leave it, the harder it may be to return to target.
2. Keep using FastDay every day or at least on most days
It is important to keep tracking your weight and other measures. Even when you have worked out a method that keeps your weight stable, continuing with tracking your weight is worthwhile. It is all too easy to become a little complacent and gain weight without really noticing unless you keep on tracking. You might not notice that you are always eating more than your calorie allowance on your fast days, or are shortening the length of your fasts, or that you are eating more snacks or treats on non-fast days than you were, or that you are skipping fast days because they are not convenient. People who weigh themselves regularly have been shown to be more likely to maintain their weight loss.
Check in regularly with the FastDay community for support and ideas on how to keep your weight maintenance on track. There is a thread on the FastDay forum each month for maintainers to post how their maintenance is going.
3. Keep motivated
When we are losing weight, we have the excitement of regular new numbers on the scales or tape measure to look forward to. When maintaining there should be no surprises on the scales or tape measure. You won’t get any ‘have you lost weight?’ comments to make you feel proud. Nobody seems to congratulate you for staying the same size! It is hard to keep motivated when we do not see a ‘reward’ for our efforts.
Ideas on how to maintain motivation:
Visit the FastDay forum and connect with other maintainers
Calculate how much weight gain you have avoided! Suppose that on each fast day you are eating 1000 calories less than on you do on your non-fast days, then each week you are ‘saving’ 2000 calories. If it is true that 1kg of fat is ‘worth’ 7000 calories then each week you have prevented a fat gain of 300g or over 1 kg per month of successful maintaining!
Celebrate your maintenance anniversaries: the first month, 6 months, 1 year, 2 years etc. by posting on FastDay and inviting people to congratulate you. Or treat yourself to a non-food-based reward like new clothes.
Post your story on the FastDay inspirational stories section to advertise your success and give you that feel-good factor once more. Write a blog about your journey, and share pictures with your friends.
Have a maintenance buddy from the FastDay community so you can encourage each other.
Mentor people who are currently trying to lose weight, giving them much needed support but at the same time reminding you on how well you have done.
4. Keep on exercising
Many people will increase their exercise to help lose excess weight, but when the goal weight is reached, perhaps they ease up on their exercise levels. This combined with the now lower energy needs due to weight loss can be a recipe for weight regain.
Toning your muscles through exercise can further improve your body shape and composition – you will look and feel even better!
Exercise brings so many health benefits there is no need to reduce it now you have lost weight.
If the exercise plan you are currently following is losing its appeal, look for alternatives.
5. When you get knocked off course, get straight back on again
Changes in routine such as holidays, or going through a busy, stressful time, can result in changes in eating habits – and you may decide to reduce or skip some fasting. When you have the stress under control, or the holidays are over, it’s time to return to fasting. One of the great joys of IF is that a maintainer can simply have a burst of more intensive fasting for a few weeks to get back to target weight if something in life causes them to have put some weight on. It can sometimes be hard to return to your old routine after these changes but if you keep delaying re-starting you risk continued weight gain.
Plan in advance when you will do your first fast
Tell people about your plan – post about it in the FastDay community
Make sure you stick to the plan
Once you have got that first fast out of the way, you will soon be back in the old routine and any weight gained will disappear.
Surprisingly, there have been very few scientific studies looking at what makes for a successful weight-loss maintainer. One study in which researchers studied 4000 people who had lost at least 13.6 kg (30 lb) and kept it off at least one year (average loss 33kg, average duration of maintenance five and a half years) was able to identify several features that characterised successful weight maintenance.3,4 These included:
Keeping their calorie consumption under control
Doing high levels of physical activity
Weighing themselves frequently.
People who had failed to maintain their weight loss were more likely to have suffered from depression, to have episodes of bingeing or to have lost relatively small amounts of weight.
But the most important factor of all was how long people had successfully maintained their weight loss: those who had kept their weight off for two years or more had a nearly 50% better chance of continuing to maintain their weight over the following year. The longer you can keep the weight off, the easier it will be for your new weight to become permanent.
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When should I enter weight maintenance?
You probably set your goal weight some time ago without really knowing whether it was an appropriate target for you. Along the journey towards this goal you will have learned a lot about your body and how it responds to fasting and to the food you eat. You will have seen changes in your shape as well as your weight and may have changed your mind about your final target.
As you get closer to your target weight, you will probably find your weight loss is slowing or maybe it seems to have stopped. Perhaps you are wondering whether you will be able to reach the target you set yourself. It is time to think about maintenance strategies. The first question is: when exactly should I enter maintenance?
It’s time to enter maintenance when:
You’ve reached your target weight, you have a healthy weight/waist measurement and you look and feel just great!
You’ve not reached your target weight but you have stopped losing weight and don’t feel that you could sustain adding more fasts or more restrictive eating.
It might be time to enter maintenance when:
You’ve not reached your target weight but your family and friends are saying that you are looking too thin – get them to take some photos of you for you to see what you look like to others (sometimes the mirror is not an accurate guide).
You’ve reached your target weight and although you’re still carrying a bit more fat than you’d really like your weight loss has slowed dramatically.
You are feeling that the fasts are becoming hard work.
It’s not time to enter maintenance when:
You’ve reached your target weight but your waist still measures more than half of your height and you are still losing weight relatively easily.
You have not reached a healthy weight but family and friends are suggesting you stop now – it’s your decision when to stop not theirs!
Once you have decided that it is time or nearly time to enter maintenance, you’ll need to think about whether you need to change your current Way of Eating and how you’ll monitor your weight, what rules you’ll set for allowed weight gain/loss before taking action and, importantly, how to keep motivated so that you will successfully maintain your lower weight in the long term.
What fasting method is best for weight maintenance?
Some people find they need to reduce the amount they are fasting when they reach maintenance because they continue to lose weight. Others find that they can continue with their previous fasting method but allow themselves to eat a little more, say increasing their fast day calorie allowance from 500 to 700 calories. There are many different fasting strategies that will work well for weight maintenance.
There are so many myths about weight loss and fasting! Some of them are rooted in traditional beliefs – the kinds of things our grandmothers used to tell us. Others may have been promoted by powerful lobbyists in the food industries. Many more could be called ‘things scientists used to believe before they found out more…’
Below we have covered some of the most common myths. Millions of people could live happier and healthier lives if only they knew that these beliefs are myths and not based on the best evidence and science.
Breakfast prevents obesity
The myth
Many of us love to have a good breakfast, and find it makes us feel great, setting us up for the day. So what’s the myth? Many people believe that eating breakfast prevents obesity and that skipping breakfast regularly will ‘backfire’ and lead to a weight gain. You might hear people say that breakfast ‘kick-starts your metabolism’ for the day, increasing your metabolic rate.
The truth
The truth is that eating breakfast does not prevent obesity, or enhance weight loss by kick-starting your metabolism. In fact, the calories you consume will inevitably outweigh the effect of an increased metabolic rate.
At FastDay we work hard to stay up to date with the latest scientific research, and to make the latest evidence available in an easily-understandable form. Scroll down to the section ‘More information for the scientifically inclined’ for more about the evidence around breakfast eating.
What you eat for breakfast is important, of course. Breakfast can often be a meal loaded with carbohydrates, including sugar – and if you are someone who likes to start the day with a meal (nothing wrong with that!) the best advice is probably to focus on eating healthily.
Many fasters have no breakfast on a fast day…or use an eating window approach and never eat breakfast at all. You might find that skipping breakfast is a great way to avoid a high carb, high sugar meal. If this works for you, you should carry on! There is no need to be concerned about the myth that skipping breakfast is bad for you or will cause you to gain weight.
Need more info? Scroll down to find more detail for the scientifically inclined.
Fasting causes the body to enter a ‘starvation mode’
The myth
We are told that eating less than a certain amount of calories daily will cause the body to enter a state termed ‘starvation mode’ in which it ‘hangs on to fat’. Some people are worried that intermittent fasting may have this effect on them – and may even cause them to gain weight.
The truth
The myth is based on a misunderstanding of some famous studies into the effect of long term starvation diets on the human body. If a human eats at a ‘starvation’ level of calories for weeks or months on end, the body finds ways of reducing the impact, and a body that has lost weight now needs fewer calories each day. These factors may reduce the impact of a starvation diet but we cannot deny the laws of physics: if you are eating less calories than you are using, you must lose weight.
These famous studies are creating extreme conditions and are of no relevance to intermittent fasting, which we recommend should include fasts of no longer than 36 hours with no calorie intake or 3 days of very low calorie intake (below 800 calories).
The bottom line is that If you choose to pursue intermittent fasting as a permanent and healthier Way of Eating, you do not need to worry about a mythical ‘starvation mode’.
Need more info? Scroll down to find more detail for the scientifically inclined.
A lot of research has been done on the subject of whether it is better to eat 2–3 meals a day or 6–7 smaller meals. This is a complex area, and in truth the results are mixed, with no clear winner.
Some people misunderstand this research, and think that advice to eat little and often means that intermittent fasting must be bad for you. This is a myth!
The truth
There is a large and growing body of evidence on the benefits of intermittent fasting to our health and its effectiveness as a sustainable and permanent Way of Eating.
By contrast, there is no strong evidence that eating more frequently is beneficial nor that skipping meals is detrimental to our health.
Some members of our community like to eat little-and-often on the days when they are not fasting, while others prefer a more conventional 2–3 meals per day. The science is not clear yet, but we suspect this will be primarily a question of personal preference. What we do know is that no one should pass up the benefits of fasting as result of a misplaced worry about the possible pluses of eating little-and-often.
Need more info? Scroll down to find more detail for the scientifically inclined.
We should eat a low fat, high carbohydrate diet
The myth
Since the 1970s and 1980s, governments and doctors have been advising us to eat a low fat diet and to obtain over half our calories from carbohydrates.
The truth
More recent research has shown the advice to go low fat and high carb to be misguided. In fact a low fat, high carbohydrate diet is possibly the least effective way of losing weight. It also has worse health effects than many other ways of eating.
Even worse, if you have diabetes, pre-diabetes or a predisposition to diabetes this diet advice may be positively harmful for you. (If you are overweight, and particularly if you have a large waistline, you have an increased risk of diabetes. If this is you, take a few minutes to learn more about the health benefits of fasting).
Need more info? Scroll down to find more detail for the scientifically inclined.
Eating cholesterol and saturated fat will make you fat and damage your heart
The myth
We have all been told that eating fat, especially saturated fat, will make you fat. And that eating cholesterol will raise your blood cholesterol. And they will both damage your heart.
The latest research has shown that these common beliefs are not true.
The truth
The latest research suggests that:
1. The studies consistently show that diets that are high in fat but low in carbohydrates lead to much more weight loss than diets that are low in fat but higher in carbs. Fat contains a lot of calories – but the good news is that it tends to reduce the appetite. If you are choosing between high fat and high carb, choose high fat!
2. The real problem occurs when fat is combined with sugar and refined carbohydrates (as in cake, cookies and ice cream). The combination of fat and sugar is calorific and also stimulates our appetites – it is the combination of fat with carbohydrate that is fattening, not the fat itself.
3. Including saturated fat and cholesterol in the diet does not worsen our blood cholesterol levels. In fact, saturated fat tends to increase high density lipoprotein (HDL – the “good” cholesterol) and changes the low density lipoprotein (LDL) from small, dense particles which promote heart disease into large, light LDL particles which are not bad for the heart. By contrast, eating sugar and refined carbohydrates will worsen your cholesterol profile.
4. Be careful though, as not all fats are the same. There are two kinds of fat that are dangerous to your heart and that you should avoid:
Trans fats are monounsaturated fats that have been put through a hydrogenation process to lengthen their shelf life of the fats and make them resemble saturated fats in consistency. They are mainly found in processed foods and are strongly associated with an increased risk of heart disease.
Vegetable oils that are very high in omega-6 fatty acids such as soybean and corn oil, which are also strongly associated with heart disease risk.
The bottom line: there is no need to avoid saturated fats in your diet, but it is advisable to limit consumption of refined carbohydrates such as sugar, sugary foods and drinks, white flour, pasta and rice and to avoid trans-fats and oils high in omega-6 fatty acids.
Need more info? Scroll down to find more detail for the scientifically inclined.
I’ve found a food supplement that will change my life!
Snake oil supplements? Scientific evidence for popular nutritional supplements
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The myth
There are so many dietary supplements that are claimed to speed up weight loss as well as improve your health in multiple ways. Green tea, coconut oil, garcinia camboga, chromium, guarana, seaweed tablets, yerbe mate, and many more…is there any truth in their claims?
The truth
Losing weight can be such a slow and difficult process (unless you have discovered the power of intermittent fasting, that it), it’s hardly surprising that diet supplements claiming to boost weight loss are big business, but few have any real evidence of effectiveness. And even those that have some scientific evidence provide such a tiny improvement in speed of weight loss that it is hardly noticeable outside of a scientific study and is certainly not worth the expense of paying for.
We love this chart showing how well-founded the evidence is for a huge range of supplements marketed for a wide variety of health conditions. It is based on work by the Cochrane Collaboration a well-regarded and not-for-profit medical research organisation.
Use it to find the supplements that you or your friends have been talking about – and to identify the many myths and snake oil salesmen that exist. Many supplement companies are just people looking for your money, and won’t bring you any benefit.
At FastDay, we think that spending your money on supplements is not generally a good idea – and that you should be careful if you want to take dietary supplements. Many of these products carry a substantial health risk.1
By all means have a cup of green tea while you think about it! (but even green tea seems to increase the metabolic rate and alertness primarily because it contains caffeine2 and some serious side-effects have been reported).
More information for the scientifically inclined
The evidence around breakfast eating
Most of the scientific studies into the value of eating breakfast have had serious flaws in their design and how the results were interpreted by the investigators.
A recent paper in the American Journal of Clinical Nutrition castigated studies aimed at investigating skipping breakfast.3 The paper reports the results of an in-depth analysis of the available research, not only looking at the results of 92 unique articles, but also evaluating whether study results were accurately communicated in the abstract section of the article and whether articles correctly described prior research results. The authors report that “Four examples of biased research reporting are evident in the literature as follows: 1) biased interpretation of one’s own results, 2) improper use of causal language in describing one’s own results, 3) misleadingly citing others’ results, and 4) improper use of causal language in citing others’ work.”
The lead author of the paper, Andrew Brown said “We specifically found that research articles tended to overstate the strength of study designs and ignored evidence that did not support the proposed effect of breakfast on obesity.” He continued, “These distortions leave readers believing that the relationship between breakfast and obesity is more strongly established by science than the data actually support.”4
On his website, Dr Brown says, “So how did ‘breakfast prevents obesity’ come to be so widely believed? The common refrain is that lay media misunderstand and miscommunicate research, and that the benefits of breakfast on obesity is a conspiracy of breakfast-food companies. However, we demonstrated that the primary literature often overstates the known relationship between breakfast and obesity. In particular, we showed that there is a substantial use of causative language when describing observational evidence about breakfast and obesity, both when researchers cited others’ work as well as when summarizing their own work. In addition, there is evidence that researchers misleadingly cite others’ studies to support the presumed effect of breakfast on obesity. Specifically, when authors would cite a study that had results both supporting and refuting the breakfast-obesity hypothesis, authors often would exclude the information against breakfast. Even in their own abstracts, there was a tendency for authors to only make conclusions about breakfast and obesity when the results were in favour of eating breakfast.”5
There are many reasons why more people who skip breakfast might be overweight than those who do not skip breakfast. For example, what does ‘skipping breakfast’ actually mean? Do the breakfast skippers have a couple of chocolate bars at 10 am at their coffee break? Are the breakfast skippers missing breakfast because they are trying to lose weight? Are the breakfast skippers eating snacks late at night instead of eating a ‘healthy’ breakfast thereby taking in more calories than if they had eaten breakfast and not snacked late at night? Are people who find they don’t want breakfast more prone to obesity because of some other metabolic feature that both promotes obesity but also makes people not want breakfast?
The only long-term, carefully controlled trial that randomly assigned people to routinely eat or go without breakfast and then measured the effect on their body weight was published in 1992.6 In that study, moderately obese adults who were habitual breakfast skippers were put on a diet that included eating breakfast every day for 12 weeks. They lost an average of roughly 17 pounds. However, another group of regular breakfast eaters who were instructed to skip breakfast daily for 12 weeks lost an average of nearly 20 pounds. Both diets included an identical amount of calories, and each caused people to lose more weight than a diet in which a person’s typical breakfast habits did not change.
Another study examined the effect of eating breakfast on calories burned by assigning a group of people to eat breakfast for one week and then to skip breakfast another week. They found no difference in energy expenditure between the two weeks (i.e., no more calories were burned).7
Regarding the claims that eating breakfast boosts metabolism, there is a phenomenon, termed ‘diet-induced thermogenesis’ or the ‘thermic effect of food’. This refers to an increase in metabolism after eating which represents the energy needed to digest the meal eaten. It is, with basal metabolic rate and activity induced thermogenesis, one of the three components of daily energy expenditure, albeit the smallest component. Most studies investigating the amount of calories burned after eating compared with the calories in the food eaten have reported that the energy expended due to diet-induced thermogenesis is less than 10% of the energy content of the food ingested.8 Thus, the calories eaten with breakfast will be 10 times greater than the calories burnt from eating it!
The science of starvation mode
The myth of starvation mode may have arisen due to misinterpretation of the results of several studies. Perhaps the most commonly quoted study is the ‘Minnesota starvation experiment’ conducted by American doctor, Ancel Keys.9,10 This experiment conducted towards the end of the Second World War aimed to discover how to deal with victims of mass starvation in Europe. Conscientious objectors in the US and the UK who had volunteered for medical research were starved for six months, given about 1600 calories at day, which was about 1600 calories per day less than they needed – at least at the start of the experiment. You will likely have heard it said that to lose one pound (0.45 kg) of fat you need to eat 3500 calories less than you burn. Using this calculation the expected fat loss after 24 weeks of starvation would be around 78 pounds (35.5 kg) of fat. In fact, the average weight loss of the men was less than half of this – 37 pounds (16.8kg). The reason for this is clear: while the men may have needed 3,200 calories, on average, to maintain their weight at the start of the experiment, as they lost weight and their energy need fell and so their weight loss slowed. In addition, their metabolic rate decreased further reducing their energy needs.10 This reduction in energy needs with weight loss has been investigated in many studies, with varying results. Some studies have suggested that the amount of calories needed to maintain a 10% reduction in body weight may be 10–15% less than would be predicted solely due to alterations in body composition and weight. Others have not found this.
What about fasting? Does fasting slow your metabolism? In studies of short-term fasting (3 days), the metabolic rate of the participants actually increased.11,12,13
The bottom line: It is true that after many weeks of calorie restriction your body’s does make certain alterations to reduce your energy needs so that you may not lose weight as quickly as you did at first. In addition, as you lose weight and so are lighter you need less effort to move around and so your exercise and daily activities consume less energy than they did before. But if you are eating less calories than you are using, you must lose weight.
The idea that we need to eat every few hours is a rather strange one. At one time parents used to say to their children “you must not eat between meals or you’ll spoil your appetite”. But sometime in the last 20 years the advice has changed to “eat several small meals a day.” The reasons given for eating frequently seem to vary. Some say it boosts your metabolism, some say it keeps blood sugar stable, some say it prevents over-eating.
The origins of this myth of a metabolism boost from frequent eating lie in studies done in the 1960s and 70s in which researchers found that overweight individuals were more likely to eat only one or two meals a day compared with normal weight people.13 However, more recent studies examining meal frequency in more detail that have documented how many calories are consumed and how much energy expended on a regimen of 6–7 meals per day versus 2–3 meals a day have found no difference in energy expenditure but that frequent eating is more likely to result in a higher calorie intake.13 It appears that the early studies were flawed by the way in which the data were collected: when over-weight people were asked how often they ate, they tended to ‘forget’ to mention a lot of eating!14 When this under-reporting of food was taken into account it became clear that frequent eating, particularly snacking, results in greater calorie intake.
The question of frequent eating and stabilising blood sugar is a bit more complex. Some studies have indeed found that eating frequently resulted in more stable blood glucose values than eating fewer meals.15 However, the average blood glucose levels of people who eat fewer meals is lower than those who eat frequently.15 As changes in blood glucose are affected principally by the composition of the food eaten, the types of meals and snacks used in these kinds of experiments may influence the results.
Lastly, the evidence for frequent eating being able to regulate appetite better is also mixed.14
The experiences of our FastDay community, however, have shown repeatedly that fasting reduces appetite. Again, the experimental results may have been affected by the composition of the meals: changes in blood sugar stimulate appetite and high carbohydrate foods tend to be less satiating than high protein or high fat meals.
The bottom line: There is no strong evidence that eating more frequently is beneficial nor that skipping meals is detrimental to our health. By contrast, skipping meals (fasting) may be good for you.
The reasons why this health advice has become the standard message in countries around the world are due to a combination of poorly designed, misinterpreted observational studies, assuming that experiments in animals that have a very different diet and metabolism to humans could be extrapolated to us, and a series of political manoeuvrings by companies who would benefit from such advice. Since the introduction of this advice, the rates of obesity and diabetes have soared. This may be a coincidence but then again, perhaps not. Let’s look at the evidence.
Many studies have been conducted on the low fat diet and most have found that its effectiveness for weight loss or health is modest at best. The biggest diet study ever conducted, The Women’s Health Initiative, which involved 48,835 women who were assigned to eat either a low-fat diet, or to continue eating the standard Western diet.16,17,18 The women were followed for 8 years and at the end of the study, there was only a 0.4 kg (1 lb) difference in weight between the two groups and there was no reduction in heart disease or cancer.
Recently, a Swedish Expert Committee published their findings of a two-year investigation into all the studies on treatment of obesity through diet.19 They found that advice on strict or moderate low carbohydrate diets is a more effective means of achieving weight loss than advice on low fat diets in studies up to 6 months. The studies consistently show that diets that are high in fat but low in carbohydrates lead to much more weight loss than diets that are low in fat but higher in carbs.20,21,22
Looking at the longer term, they found no differences in the effect on weight loss between advice on strict and moderate low carbohydrate diets, low fat diets, high protein diets, Mediterranean diets, diets aimed at achieving a low glycaemic load or diets containing a high percentage of monounsaturated fats.
Even the claim that saturated fat is bad for you has not stood up to scrutiny. In fact, studies have shown that in humans (as opposed to animal studies) saturated fat tends to increase high density lipoprotein (HDL – the “good” cholesterol) small, dense particles which promote heart disease into large, light LDL particles which are not bad for the heart.23,24,25 By contrast, eating sugar and refined carbohydrates will worsen your cholesterol profile.26
The bottom line: a low fat, high carbohydrate diet is possibly the least effective way of losing weight and does not bring better long-term benefits than any other diet. It may, in fact, be harmful if you have diabetes, pre-diabetes or a predisposition to diabetes.
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What are the side-effects of fasting?
Some people experience side effects in the first few fasts. At this time your body is learning to adapt to using your stored fat as its energy source. If it has been a long time since your body has had to rely on its fat stores, it may be slow to start up the mechanisms needed to use fat as a fuel. This phenomenon, termed ‘metabolic inflexibility’, is often seen in people who are overweight. The side-effects due to metabolic inflexibility occur only during the first few fasts and rapidly improve.
The kinds of problems you might experience during your first fasts are:
Headaches: make sure you are drinking enough and if they are bad, take a pain-killer
Light-headedness or dizziness: a few people have a ‘spaced-out’ or light-headed feeling. Often, all that is needed is a salty drink or food.
Feeling very tired, especially mid-afternoon, is because your body has not yet learned to access your fat stores for fuel. A salty drink can help with this too.
Becoming short-tempered can be a problem towards the end of the fast, especially as the time to eat approaches. Planning your food ahead of time can help, and being aware that you may be short-tempered can help you to be calm around your friends and family.
Insomnia is common on the night of your first few fasts.
Constipation/diarrhoea on the day after your fast may occur as your body reacts to the new way of eating.
Longer-term side-effects
Experienced fasters can occasionally have a repeat of these kinds of symptoms. Often it is due to having eaten a lot of carbohydrate in a short period, drinking more alcohol than usual, or having a stressful day just before the fast day. All of these can tip your body out of fat burning and back into sugar burning.
The two most common ‘occasional’ side effects we hear about are:
Constipation due to very little food intake on fast days.
Poor sleep after the fast day due to increased alertness triggered by fasting.
In fact most of the other ‘side effects’ our community talks about are a result of losing weight rather than because of fasting. For example:
Saggy skin if you lose a lot of weight.
Increased hair loss, particularly if you lose weight rapidly.
Change in menstrual cycle in women which is likely due to release of oestrogen that is stored in the fat held in your adipose tissue. As the fat shrinks, the oestrogen is liberated.
Dealing with cynicism and pessimism about fasting from others
When you have lost some weight and people start to notice, they will almost certainly ask you how you managed it. Or you may be so excited by this new Way of Eating that you mention your new-found health tool to people. Most will be interested and pleased for you, but there may be a few who respond negatively. They may treat intermittent fasting as a fad diet and say gloomily that you will likely put all the weight back on again in a year. They may think that by fasting you are harming yourself. They may just be suspicious of this new approach. A very few may become quite hostile to the idea. You might be somewhat disconcerted by these reactions, especially if they come from a close friend or family member.
Why do people sometimes respond in this way and how can you deal with them?
Cynicism: “It’s just a fad diet and you’ll put the weight back on”
There are so many fad diets (definition of a fad diet: “a weight-loss diet that enjoys temporary popularity”) that come and go in fashion, especially after traditional times of excess eating, that it is hardly surprising that when people hear of a new diet that involves (to them) new ideas, they immediately dismiss it as a ‘fad diet’.
The term ‘fast diet’ and ‘fasting’ has also made people to jump to conclusions: either that ‘fast diet’ means rapid weight loss or that ‘fasting’ means living for weeks on water or juice alone.
Most people think of fad diets as being short-term weight loss tools and that you won’t keep the weight off but the sad truth is that people advised by nutritionists to adopt a healthy eating plan don’t end up keeping the weight off either.
How to respond:
Point out that people have fasted intermittently for centuries as most of the world’s religions traditionally incorporate periods of fasting.
Point out that everyone fasts every single day of their lives – unless they eat in their sleep that is – and ‘breakfast’ (to break your fast) is a term that scares nobody.
Point out that thousands of people using FastDay have lost weight and kept it off by fasting, and are continuing to fast after following the fasting Way of Eating for over a year – hardly a fad diet!
Most skepticism comes from a lack of understanding of what intermittent fasting means together with the number of health and weight loss myths that have been circulating about the need to eat breakfast, to boost metabolism by regular meals and to avoid ‘starvation mode’.
Pessimism: “You are harming your health by fasting”
People who have strong beliefs about nutrition and health may take the view that fasting will harm your health. Unfortunately, some ‘experts’ who have commented about the fast diet and intermittent fasting have done so without investigating the scientific basis for this Way of Eating and have passed on the view that fasting is not healthy to their readers/listeners. Further, the Fast Diet has been reported inaccurately in newspapers and magazines as ‘eat as much as you want for five days and starve for two’. Actually the formula is ‘eat normally for five days and fast for two’.
How to respond:
Explain that, on the contrary, fasting could be the best thing one can do for one’s health.
Say that fasting has been shown to prolong the life of animals in studies
Say that fasting has been shown to improve the risk factors for several diseases in human studies
Tell the person to watch the documentary by Dr Michael Mosley about fasting
Tell the person to read the books by Dr Mosley or Dr Varady
Fear of change: “You’ll get thin and then I’ll be the fat one”
People who are normally very polite can become surprisingly vocal when the topic is weight or weight loss. Often those who love to give weight-loss advice could do with losing some weight themselves! Perhaps this hostility comes from fear that a new, slimmer and more confident you would reject them, or be less amenable to them. Some people find change particularly threatening, especially when it is being actively sought by someone close to them.
How to respond:
When this happens, try to think ‘”it’s their issue, not mine”, keep smiling and carry on doing what you want. all you can do is carry on as normal, whilst being reassuring about the things that aren’t changing.
Fear for their own health: “Perhaps my eating habits are not so healthy”
Some people may react with hostility because of a personal feeling of guilt. Maybe you have turned down cake with coffee because you are fasting and your friend has ordered a large slice of chocolate cake for themselves – there is something strange about eating in front of someone who isn’t. Your friend may try to persuade you to break your fast and have a piece of cake. Remember this sabotaging behaviour is probably due to their personal anxieties about food.
Alternatively, perhaps this person is struggling with their weight and the suggestion that something different could work better, or that they might be doing something wrong (even if you have not said anything of that kind), can trigger a defensive reaction through fear.
How to respond:
Remember that it’s their issue, not yours, keep calm and change the subject.
Just say ‘ ok I respect your opinion’ and move on.
Adverse comments from family members
You will, almost certainly, want to tell your close family what you are doing. If a family member reacts badly to your fasting, remember that you are not requesting their approval nor permission – you are taking control of your life, not theirs. You are an adult and can make your own decisions. If your family feel they need to raise the issue repeatedly, it is best if you refuse to discuss it. Change the subject, just say ‘ ok I respect your opinion’. If necessary, calmly remove yourself from the room or the house without a word. They will then have no audience and will soon stop. It may take a few (maybe a lot) of quiet refusal before they learn that it is just not working.
You may feel that you would rather not tell one or more of your family members. Perhaps if you have young children who have food-related issues themselves for example. Most of us are brought up to be honest – but sometimes for the sake of our own health and sanity we must be less than honest – a little subterfuge can be used to disguise your fast days:
Saving all your calories for the evening meal will give you a substantial meal that will look the same as the rest of the family is eating. Perhaps your portion will have no/less potatoes or rice because “I had a big lunch” or “I’m not so hungry today”
You can get up a bit late and say you’ll grab something to eat for breakfast at work.
You can say you are going to have a couple of low calorie days a week so as to be able to enjoy the weekends (true!).
Generally, though, it is best to tell your family what you are doing fairly soon. They will soon notice that you are losing weight and may worry that you are ill if you don’t tell them that you are actually trying to!
Our FastDay forum members have found the following tips useful in dealing with people who are skeptical about intermittent fasting.
Lead by example
Of course, the best way of showing the doubters that intermittent fasting is a sustainable, effective way of improving your health is to show them your success.
FastDay forum member Ballerina said:
“When it became obvious I had dropped quite a bit of weight, 21 lbs, people began asking questions and commenting on how well I looked. I now seem to be something of a mild celebrity and champion of the diet round here as friends are now asking me to explain, to folk I do not even know, how it all works. The thing is, it’s difficult to rubbish something when you are faced with a startling success story. Just ignore negative, jealous people and carry on.”
Avoid the F word!
It is often the word ‘Fast’ that causes people to respond negatively, so why not simply avoid using it?
FastDay forum member Joyful Janet said:
“At my last weigh & measure at my gym I was asked how I was managing to lose weight. I guessed they would be anti- fasting because I have often been told not to miss breakfast, and to make sure I ate something before exercising to ‘keep up your blood sugar levels’. I said I am calorie counting, but allowing myself more at weekends and making up during the week by having a couple of low calorie days in order to have an average daily intake of around 1500 calories. That was fine with the instructor. I haven’t really talked about this Way of Eating to anyone else except my close family, who are all so used to me trying all sorts of diets that they just let me get on with it.”
FastDay forum member BruceE said:
“I prefer to describe what we do as ‘eating less and exercising more,’ which is not at all controversial, and I like the term ‘repair day’ or ‘light day’ to ‘fast day.’ Tell them that repair days serve at least two functions: (1) they help to create a weekly caloric deficit (i.e. eating less), and (2) they help to manage your appetite/hunger while you are eating less. There are of course other benefits to not eating for 16–24 hours before ‘breaking your fast’ instead of the normal 8–12 hours everybody does most days, and phrased in that way, because there is nothing controversial about ‘breakfast,’ it comes off as less-severe. In fact, technically-speaking, nobody ever skips breakfast. Whenever you break your daily fast, that IS breakfast!”
Remember that in reality it is their problem not yours
FastDay forum member Ballerina said:
“I didn’t tell people what I was doing, but when it became obvious how much weight I had lost, and how well I looked, the questions started. Funnily enough all my slim friends see nothing wrong with it, or my weight loss, but strangely, all my overweight friends INSIST on telling me that I MUST NOT lose any more weight! They proclaim, quite proudly, that they could never do such a thing, which is, frankly, obvious. It seems to me that if you can’t, or won’t, do something then rubbishing it will make the reality of your own shortcomings painful to face up to, a sort of survival tactic I suppose.”
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Some people get headaches or feel they have low blood sugar when they start fasting. Or they have trouble coping with hunger pangs. Later on they may hit a plateau after a few weeks’ or months of weight loss. Or they are ill, or go through a stressful time in life.
Our community has experienced all of these things, and FastDay has collected lots of valuable support and advice for you.
Intermittent fasting can be an effective way of losing weight and managing type 2 diabetes. Many members of our community with type 2 diabetes are now free of diabetes medications, or have seen significant improvement.
Fasting is not for everyone. If you have a medical condition, check with your doctor. Intermittent fasting is not recommended for children, people who are underweight, and women who are pregnant or breast feeding.
The Fast Diet book was written by Dr Michael Mosley and Mimi Spencer, and was based on Dr Mosley’s BBC Horizon documentary called Eat, Fast and Live Longer. It has proved a hugely popular guide to intermittent fasting and has sold over one million copies worldwide in its first year. It is focused on the 5:2 fasting pattern.
Why fasting works better than Weight Watchers (and the others)
You will lose more fat but less muscle by fasting than you would on a conventional weight-loss diet.
You’ll also find fasting much easier to stick to. You fast only for short periods: one or two days a week, and the rest of the time you are free to live normally. You can be a faster for life, not just for a few weeks.
If you are overweight, you undoubtedly know that losing weight will be good for your health. But the latest scientific research suggests that there are likely to be health benefits from fasting, over and above the benefit of weight loss. These include reduced risk from conditions such as diabetes, heart disease, cancer and Alzheimer’s disease. We’ll keep you posted as the science develops.
Intermittent fasting regimes like The Fast Diet are a great way to lose weight. Even better, fasting allows you to keep the weight off forever, and find a Way of Eating that you can stick to permanently.
Be healthier. Lose weight. Eat the foods you love, most of the time.
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