Even if calorie restriction does not help anyone live longer, a large portion of the data supports the idea that limiting food intake reduces the risks of diseases common in old age and lengthens the period of life spent in good health.
– Scientific American

The second of Michael Mosley’s PBS series on health is titled Eat, Fast and Live Longer.  A significant portion of the program is devoted to the health effects of fasting or caloric restriction.  (He does not suggest that you actually consume your food at a rapid pace.)  I’ve read and heard about some of the benefits of fasting and I’ve played around with it a little bit.  After understanding the results of Mosley’s self-experiment with fasting, my wife and I both were very motivated to enact some form of fasting in our lives.

Michael Mosley PBS

Watch Eat, Fast and Live Longer with Michael Mosley on PBS. See more from Michael Mosley.

Benefits of caloric restriction

There seem to be several noteworthy benefits to fasting (aka caloric restriction.)  I’ve written before that hunger actually seems to stimulate movement and alertness.  The idea being that a hungry animal must go look for food.

Also, caloric restriction seems to extend the lifespan of various organisms and reduce incidence of various diseases. (Many studies have been done on animals, others in humans.) Caloric restriction seems to improve insulin sensitivity, heart function, and seems to improve memory in the elderly and may help in epilepsy treatment.  Fasting seems to make brain tumors more vulnerable to radiation treatment, and calorie restriction–particularly carbohydrate/sugar restriction–appears to be an effective treatment for other cancers.  (To be fair, there are other studies finding few benefits to calorie restriction.  A recent study in monkeys suggests that the type of calorie matters more to lifespan than the amount of calories consumed.)

In this episode of Mosley’s show, he discusses Insulin-like growth factor or IGF.  I won’t go into all the details of this compound, but it seems that it plays a key role in the development of several cancers and diabetes.  In a study from the Journal of the National Cancer Institute, subjects with breast cancer, prostate cancer, colon cancer and ovarian cancer had higher levels of various types of IGF compared with controls.  The study says:

“Evidence suggests that lifestyles characterized by a high-energy diet may affect the IGF system, which may, in turn, connect such lifestyles to high rates of cell proliferation and predispose cells to risk of malignant transformation.”

An article in the Harvard Gazette discusses studies with similar findings.

Why is this important?

Fasting decreases levels of IGF.  Beyond just cutting calories, protein needs to be reduced as well. Watch Mosley’s special or read his BBC article The Power of Intermittent Fasting for more discussion on fasting and IGF.

I’m not a true academic researcher and I don’t claim to have found all the definitive evidence of this whole IGF/disease relationship, but from what I’ve read and heard it sounds like too much food may push us towards some types of diseases including various cancers.  Periodic caloric restriction seems generally like a good, healthy idea.

If you look at the Wikipedia entry for fasting, you’ll see that the practice has been around all over the world for thousands of years, often for religious purposes. I tend to think though that if a practice hangs on for that long, our organism must on some level see something beneficial in it. Further, as noted in the Scientific American article How Intermittent Fasting Might Help You Live a Longer, Healthier Life, ancient humans were often forced to fast due to availability of food.  A reliable supply of three (or more) square meals a day is a very recent addition to humanity.  It’s possible that this pressure in evolution helped select for healthier genes that survive today.

In the next entry, I’ll discuss various types of fasts and my early experience in toying with caloric restriction.