Why Is Fasting Beneficial?

 

Our bodies have not evolved since the days when food was not always to hand as it is for most of us in the Western world today. In prehistoric times, one day we might have a hairy mammoth to feast on, but the next and the next after that there might be nothing. 

Furthering our species is dependent on growth and reproduction, which require food for energy.  So when food is plentiful our bodies produce lots of a hormone called Insulin-like Growth Factor (IGF-1) that encourages growth and energy output. 

But the relentless and continuous production of IGF-1 has been likened by Prof Valter Longo, of the University of Southern California’s Longevity Institute, to driving a car continuously with your foot flat to the floor and never having it serviced. In other words it’s soon going to break down. 

But when fasting, the body realizes that growth is not a good idea and reduces production of IGF-1.  Prof. Longo explains that not only does this take the foot off the accelerator, but it also allows the ‘mechanics’ (in this case your immune system and other factors at work in your body) in to do some repair and maintenance.  Although important when we are young and growing, as we age high levels of IGF-1 are linked to diseases including cancer and diabetes which are shortening modern lives.  Prof. Longo studied special mice, which were resistant to the effects of IGF-1.  As well as being smaller than other mice, they live twice as long, especially when they are fed calorie-restricted diets.  (That would be like humans living to nearly 170 years old!).  As long ago as 1945 it was found that intermittent fasting increased the life-span of rats.  It is only more recently that we have gained a better understanding of why this might be.

These start maintenance processes during which old, worn out cells are removed and replaced.  This is thought to be protective against aging and developing certain cancers. While the body is motoring along under the influence of lots of IGF-1, it is thought that there is no time for this essential disease-preventing maintenance.

Is it calorie restriction or fasting that produces benefits?

Both, actually, and here is why. Calorie restriction switches the body out of growth mode and reduces the levels of IGF-1 that are produced, but fasting seems to have specific benefits too. Two groups of rats were fed the same high-fat diet, with the same number of calories. One group could nibble away all day on the food, while the other group only had 8 hours to eat it, fasting for the rest of the time. Although both groups ate the same number of calories, the group on intermittent fasting put on 28% less fat and avoided the high cholesterol and liver damage suffered by the other group.

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The benefits of long-term fasting in terms of weight loss, and prevention of diabetes and cancer will each be the subject of separate articles on this site.  

So be sure to keep your eyes open for more information here on what intermittent fasting can do for you, whether you are trying to lose weight or you simply want to prioritize your health.