12 Oct fasting for health?
Updated: 17 August 2026
I have read in a few different places that fasting can be good for your health. The first time I came across it was in the Cancer to Wellness book, where the author talks about supplying your body with juice for 30 days to give your body the space and energy to heal.
Polly Noble, the perennial cancer survivor often goes on juice fasts to treat her recurring bouts of cancer, and she is still alive! She has beat cancer more than three times. It keeps coming back for her, and she continues to stave it off, I hope she is successful again, I would miss her.
The logic seems to be, that it takes so much energy to digest food, and if you are just drinking juice, or not eating anything for a spell, then all that energy can be devoted to healing your body.
You are also eliminating toxins from your body during those times.
5:2 diet
Then I happened across the 5:2 diet, popularised by Dr Michael Mosely. The principle of this diet, which has become very popular indeed, is that you can eat anything you like for five days of the week, and eat 500 calories for women and 600 calories for men, on two non-consecutive days of the week.
People have lost a ton of weight on this diet, and apparently you get used to the hungry feeling two days a week. I guess I just wonder how sustainable it is. I really want to find an eating regime that truly is a lifestyle. It concerns me on the other five days you can eat whatever.
However, on those two days of fasting you are not going to consume all the nutrients that are required over the course of a day, even if you might get them over the course of a week.
Evidence for health benefits of fasting
There is some evidence for the fact that intermittent fasting might be good for you. A variety of animals have had their lifespans extended by as much as 30 % by eating 30 – 40 % less calories, and in a study on rats that is regularly cited, rats that fasted on alternate days had the same lifespans as those with calorie controlled diets. (1) They had lower blood sugar and insulin markers than the other rats, and there is some evidence that these kinds of diets can reduce cholesterol overall. (1)
Some studies of people who fast for Ramadan have shown that these fasts can reduce blood sugar and cholesterol also. (2) They can also reduce the incidence of IGF 1 – or the growth hormone, which is thought to contribute to age related diseases like cancer and heart disease. (3)
There is also some evidence that chemotherapy can be more effective if fasting occurs during the treatments. (4)
And that it improves inflammation markers.
Of course, fasting is not for everyone, and can be dangerous for some people, those who are pregnant or breastfeeding, those who are suffering from malnutrition, diabetes, people with a history of cardiac problems, or kidney problems. (5)
There is some evidence for the fact that intermittent fasting can increase the chances of cardiac arrest.
Additional challenges
Furthermore, there is some evidence that if you fast, your body can find it harder to lose weight on subsequent eating regimes. (6) It may be the starvation response.
There was one additional problem, in that the people who did fast intermittently were less likely to continue with this eating plan. (7) It does take a lot of willpower to repeatedly have a 16 hour period with no food. Admittedly for a good chunk of that you are asleep, but I think it can wear down your natural reservoir of will-power long term. This can lead to eating more foods that you would normally decline in the interests of good health. So, maybe it can be good to have a break from intermittent fasting every now and again, if that helps. (It might make it harder to start again).
References
1. How intermittent fasting may help you live a longer and healthier life. Scientific American [Internet] 2013; [cited 2013 Oct 15] Available from: https://www.scientificamerican.com/article.cfm?id=how-intermittent-fasting-might-help-you-live-longer-healthier-life
3. The power of intermittent fasting. BBC News Health. [Internet] BBC; 2013; [cited 2013 Oct 15] Available from: https://www.bbc.co.uk/news/health-19112549
5. Susan Seliger. Is fasting healthy? [Internet] WebMD; 2013 [cited 2013 Oct 15] Available from: https://www.webmd.com/diet/features/is_fasting_healthy
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