Intermittent Fasting and Hormones by Jerry Brainum 2/23

 

Intermittent fasting has greatly increased in popularity in recent years. Fasting in various forms has been around for centuries as being integral to certain religious practices. Intermittent fasting or IF is a more recent phenomenon, but not as recent as you might expect. As the name implies, IF involves short periods of alternating fasting with eating, and recent studies have shown surprising health benefits related to IF. Intermittent fasting developed from animal studies beginning in the 1930s, when scientists working with lab animals such as rodents found that restricting the animal's food intake produced a number of health benefits, especially extended lifespan. Specifically, restricting daily calories to 35% of the usual daily calorie intake led to a significant increase in animal lifespan. This was originally shown to be true in rodents, but the same effect was later shown in a large variety of animals from fish to dogs. Why calorie restriction is able to extend lifespan has several theories to explain how it occurs. But one major theory suggests that it involves a process called autophagy. Autophagy is a process that can be viewed as an internal housecleaning in the body. Old cells are discarded and replaced with new, more functional cells. In addition, calorie restriction is thought to work by blunting the actions of a protein called the Mammalian Target of Rapamycin or simply, mTOR.

This particular protein mTOR plays a pivotal role in promoting growth, and also in promoting anabolic activity in muscle. Indeed, essential amino acids, exercise, and various anabolic hormones such as testosterone, growth hormone, and others work with mTOR to help build muscle. But the problem with mTOR is that it blocks the autophagy process and in doing so, speeds the aging process. With age, mTOR gets out of balance with another protein called AMPK that works in the opposite manner. AMPK promotes autophagy but blunts muscle protein synthesis. Excess mTOR activity with age is linked not only to faster aging but also to a number of degenerative diseases such as cardiovascular disease and cancer, the two leading causes of death. The chief benefit of fasting is that it promotes AMPK activity while blunting mTOR. That promotes autophagy, which can extend lifespan. Of course, there is a price to pay when mTOR actions are blunted, and that is decreased muscle protein synthesis and possible loss of muscle mass. That would concern not only bodybuilders but also older people who are at higher risk of sarcopenia or the loss of muscle mass with age. Sarcopenia is closely related to increased frailty and imminent mortality from all causes. An ideal situation would involve a balance between mTOR and AMPK. You would want to promote mTOR in proximity to training for building and maintaining muscle mass. You do that by ingesting essential amino acids, especially the branched-chain amino acid, leucine, the most potent promoter of mTOR, and also exercise which itself promotes mTOR activity . . .