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.

Understand How Your Body Works: Metabolism

Metabolism (i.e. the process in which food is converted to provide energy and to produce and maintain cells and tissues) is a key concept for achieving a full comprehension of body physiology and being able to improve your bodybuilding program with this knowledge. This post exposes the basic issues for understating your metabolism.

Metabolism is mainly controlled by two hormones: insulin and glucagon. The most important role of these hormones is to regulate blood glucose levels, but also the fat storing/releasing process into/from the adipose tissue. Both insulin and glucagon are produced by the pancreas, but they have opposite biological functions. If one is secreted, the opposite hormone secretion is inhibited and vice versa.

All of the carbohydrates you eat are converted to glucose by the liver before being released into the bloodstream. After a meal your blood glucose level rises as carbohydrates are absorbed. In order to avoid reaching dangerous glucose levels, this rise in blood glucose triggers a release of insulin. Insulin decreases blood sugar by moving glucose into the muscle cells to be used as an energy source or to be stored as glycogen and also by storing glycogen in the liver. When the muscles cells and the liver are full or when a great amount of insulin has been released (because blood sugar levels have risen too quickly), insulin converts and stores as fat some of the glucose instead of storing it as glycogen. This occurs because insulin shuts down your fat burn capacity and activates your fat storage capacity.

Moreover, if insulin levels get too high, this causes too much glucose to be moved into cells, producing hypoglycemia (low blood sugar). This occurs, for example, when eating high GI carbohydrates. Initially your blood sugar level spikes, and then paradoxically insulin decreases it to a lower level than before. Normally, the body would compensate this by mobilizing some stored fat, but since insulin has switched off your fat burning capacity, this is not possible. Body solves this by breaking down muscle protein for energy, because it is the tissue that consumes more calories. In addition, maintaining high insulin levels over a long period of time (e.g. eating too many carbohydrates) reduces insulin sensitivity. This motivates releasing more insulin to reinforce the reduction of blood glucose level. This is very dangerous, since keeping in this state can lead to diabetes.

You can prevent muscle breakdown and increase your insulin sensitivity by limiting high GI carbohydrates from your diet (except just after your workout) and by training, because training depletes the stored glycogen in the muscle, so when glucose enters the bloodstream, you're not force-feeding the muscles, you're just feeding them something they want and need. This also justifies why it is good to eat high GI carbohydrates just after training.

Insulin is highly anabolic. It facilitates amino acid transport into muscle cells, and also blocks many catabolic processes and due to this it is one of the key factors determining your muscle growth. Hence it is advisable to create an insulin spike just after training in order to gain mass.

Glucagon is released when blood glucose levels become too low. This hormone aims to raise the glucose levels back to normal by preparing glycogen stores to be used for energy. In addition, glucagon has the effect of stimulating breakdown of body fat to be used for energy. Glucagon also shifts the metabolism from carbohydrate burning to fat burning.

You can complement the metabolism information in this post by reading the article “Blood Sugar & Insulin” by Matt Danielsson, the article “The Blood Sugar Hormones” by Derek Charlebois and the “Metabolism” section of Muscle 101 site.

Understand How Your Body Works: Muscle Physiology

Alike anatomy, knowledge about body physiology constitutes an important basis for developing better training programs. This post summarizes the basic concepts about muscle physiology covered by Mark Strasser in his article “Muscle Types, Strength Gains, and Energy Systems used in Various Sports”. This article focuses in two aspects of muscle physiology: muscle energy systems & muscle fibers.

Muscle Energy Systems. Energy is supplied to your muscles from the food you eat, which is broken down into usable blocks of energy called ATP (Adenosine Triphosphate). ATP is the primary source of energy for muscle contraction. The energy is derived from removing a phosphate ion from ATP, resulting in ADP (Adenosine Diphosphate). Your body makes ATP available for muscle contraction through three main energy systems:

• Phosphocreatine system: This system comes into play mostly during very intense workloads lasting up to 20-30 seconds. It is very fast, and can supply ATP for more muscular contractions in milliseconds by combining ADP with the phosphate ion from the phosphocreatine molecule.

• Glycolytic system: This system is the primary energy source in activities lasting between 30 seconds and 3 minutes by breaking down muscle and liver glycogen stores. The waste product is lactic acid, which leads to muscular fatigue. This system is anaerobic, as no oxygen is immediately necessary for energy production. However, from the 3rd minute of exercise this system becomes aerobic, since energy production occurs in the presence of oxygen.

• Oxidative system: This system provides the body with energy during exercise of long duration and moderate to low intensity by breaking down the body's fat stores. It is known as the aerobic system, as oxygen is necessary for energy production.

Muscle Fibers. There are two different types of muscle fibers: slow-twitch and fast-twitch muscle fibers. Slow-twitch fibers are predominately used in endurance activities. They are not likely to grow in size as much when trained and rely mainly on the oxidative system (aerobic metabolism) to obtain energy. Fast-twitch fibers are especially activated in explosive movements. They have great potential for growing in size when trained and rely mainly on the glycolytic system (anaerobic metabolism) to obtain energy.

When training with high number of reps you activate mainly slow-twitch fibers, while with low number of reps you activate mainly fast-twitch fibers. However, sets in the 1-5 rep range don't activate as many fast-twitch fibers as sets in the 6-12 rep range. The 1-5 rep range is more appropriated for strength training without increment on size.

You can also find some additional information on muscle energy systems and muscle fibers in the “Anatomy and Physiology” section of Muscle 101 site. Moreover, Derek Charlebois provides a detailed description of the chemical reactions occurred during energy generation in his article “Bioenergetics & Energy Release”.

Anatomy & Kinesiology Lessons

Developing a successful training program is easier if you have an appropriate knowledge on the human body. It makes no sense that your main goal is to build muscle and at the same time you hardly know part of the muscles in your body. If you know how the body works, you can design compensated training programs without neglecting muscles, you can detect problems on your program easily and, especially, you can reduce the risk of injury yourself with inappropriate exercises.

Some anatomy and kinesiology lessons are the first step for acquiring this knowledge about your body. With anatomy and kinesiology, you can know all the relevant muscles and their biomechanics. A good place for finding all this information is ExRx.net (Exercise Prescription on the Net) site. ExRx is a huge site with many sections related to weight training. Sure I’m going to refer to it many times in later posts. But now we’re only interested in the “Exercise Instruction & Kinesiology” section. Here you can find:

• A graphical muscle body map with links to each muscle information.

• A muscle directory with detailed information about all the muscles. This information includes the other names used to refer to this muscle, the different heads that compose this muscle, the movements performed by this muscle (e.g. flexion, extension, abduction, adduction, rotation, etc.) with links to the involved articulations, the attachments of this muscle with the bones, the related muscles, the location of this muscle in a graphical muscle map and optionally, some additional comments about particularities of this muscle.

• An articulation directory with detailed information about all the articulations, including the movements performed by this articulation and with links to the involved muscles.

As you can see, anatomy and kinesiology information is extensive and thorough. Of course, it is not necessary to know every detail, but a general knowledge on which muscles compose our body and some notions on their biomechanics will enrich your training routines by considering often neglected (but important) muscles and will help you to prevent injuries.