The Role of Hormones on Muscle Growth & Fat Loss

There are plenty of hormones in the human body that regulate all sorts of physical development and metabolic processes. Some of them contribute in an important way to regulate the anabolic and the catabolic processes. This post reviews the main hormones involved in muscle growth and fat loss, namely testosterone, growth hormone, insulin, glucagon and cortisol, which are of primary interest for the bodybuilder.

We have already described insulin and glucagon role in a previous post dedicated to metabolism. Remember that these are antagonistic hormones responsible for regulating blood glucose levels. Insulin is an anabolic hormone which facilitates glucose and amino acid transport into muscle cells (stimulating protein synthesis and inhibiting protein breakdown), but also fatty acid transport into fat cells. Glucagon is a catabolic hormone which mobilizes glycogen stores to recuperate glucose levels as well as stimulates breakdown of body fat to be used for energy. Both hormones are controlled entirely by diet.

Testosterone is a steroid hormone which is the responsible for the development of male sex characteristics (e.g. body and facial hair, deep voice, etc.) and the maturation of sperm and male sexual organs. In addition, testosterone is probably the most important hormone for building muscle through the promotion of protein biosynthesis. This accelerates muscle buildup and regeneration, and increases your recovery capacity after exercise, injuries, and illness. In addition, protein biosynthesis also stimulates the metabolism and promotes the burning of fat. You can stimulate your testosterone production through intense exercise and adequate sleep and nutrition. In addition, some bodybuilders use natural boosters when testosterone levels begin to drop due to age.

Human growth hormone (GH), also known as somatotropin, is the primary hormone responsible for stimulating tissue repair, cell replacement, brain function, and enzyme production. GH is a highly anabolic hormone having profound effects on the growth of the skeleton and the muscles. You can naturally control your GH levels through exercise, rest and nutrition. First, intense and strenuous workouts stimulate GH release because these catabolic states require extra protein synthesis and in case of lack of energy, fat metabolization to make up for glycogen depletion. Second, most part of your total daily GH is released while sleeping, especially during REM phase. For this reason, having a good sleep is mandatory for building muscle. Finally, a high protein diet contributes also to raise your GH levels.

Cortisol is a catabolic hormone which reduces cellular synthesis, and carries out the gluconeogenesis process (conversion of amino acids from muscle tissue to glucose for energy), causing in this way muscle breakdown. On the other side, cortisol is also involved in fat mobilization. Cortisol levels are highest early in the morning and during periods of high stress (i.e. after training). In order to control your cortisol levels, you should eat first thing in the morning and right after your workout (since insulin nullifies the effects of cortisol), limit your workouts to no more of 1 hour and have a good sleep. In addition, some amino acids (e.g. glutamine) and vitamins (e.g. vitamin C) help also to control cortisol levels.

You can complement the hormones information in this post by reading the article “Nitrogen Balance, Hormone Manipulation and Recovery Critical Factors in Bodybuilding!” by Jim Brewster, the article “Hormones: How They Build Muscle and Burn Fat” by Eric Hesse or the “Hormones and Neurotransmitters” section of Muscle 101 site.