Intermittent fasting can help your body to resist the development of cancer. When we fast, blood glucose levels decrease and the body starts to use our fat stores. This protects against the development of cancer in several ways:
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Being overweight increases the risk of developing many different kinds of cancer,1 so by simply losing weight through intermittent fasting we can reduce our cancer risk.
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Fasting triggers a change from growth to repair. When our body switches to repair mode (termed autophagy), any damaged cells or parts of cells are broken down and their bits reused to make new, well-functioning cells. This particularly affects cells which might turn cancerous.
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Fasting can also reduce the amount of the hormone, insulin-like growth factor 1 (IGF-1) which has been found to be associated with an increased cancer risk. Some people seem to have particularly high IGF-1 levels and there seems to be a disproportionate number of cancer patients with high IGF-1 levels.
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The decrease in blood glucose starves cancer cells of fuel. Cancerous cells generally can’t use fats or ketones for fuel – they use only glucose – and so, whereas our normal cells can manage just fine with fats or ketones, the cancer cells are starved and cannot grow.
Learn more about what happens when we fast
Learn more about fasting and burning fat
What are my cancer risks?
More than one in three people will be diagnosed with some form of cancer during their lifetime.2 The most common forms of cancer are breast cancer (for women) or prostate cancer (for men), followed by lung and bowel cancer.2
In the UK, It has been estimated that 5.5% of all cancers in the UK in 2010, (around 17,000 cases) were linked to being overweight.2 The types of cancer that have been linked to being overweight include breast, oesophagus, gall bladder, pancreas, colon, endometrial and kidney cancers.1 Poor diet is also considered a risk factor for cancer, particularly eating too much protein and not eating enough vegetables.2
What makes cancer cells susceptible to fasting?
Cancer cells have several features that make them susceptible to fasting:
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When cells become cancerous they lose the ability to turn off growth so they keep just growing and growing. Cancer cells don’t grow especially fast, but they just don’t stop.
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Cancer cells don’t die off and get replaced like normal cells do.
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Cancer cells only use glucose for fuel. They need glucose to supply energy rapidly to fuel their endless growth.
Several lines of scientific research point towards lowering insulin resistance, reducing blood glucose concentrations and decreasing concentrations of insulin-like growth factor (IGF-1) as having potential for treating cancer:
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Diabetes patients treated with metformin, a drug that lowers insulin resistance, seem to get less cancer.3
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People with Laron syndrome (a condition in which people do not have IGF-1) do not get cancer.4
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Tumour cells grown in test tubes respond to insulin by growing but will die if insulin is removed.5
Happily, fasting achieves all of these things. Studies in animals have shown the potential of fasting for preventing or treating cancer:
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Rats who were fasted every other day for a week before being injected with breast cancer cells survived much better than their counterparts who had not fasted (50% survived compared with only 12.5% of the non-fasted rats).6
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Multiple cycles of fasting have been shown to slow the growth of tumour cells.7
- In mice, fasting reduced IGF-1 levels leading to changes in cells that promote stress resistance, self-renewal, and regeneration. Multiple cycles of fasting reversed the damage to the immune system caused by chemotherapy.8
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Fasting can also make chemotherapy more bearable, reducing the unpleasant side-effects of nausea, vomiting, hair loss and fatigue, and may even make the chemotherapy more effective.7,9