Optimizing Hormonal Responses for Maximum Muscularity and Definition
Bulletin No. 16, Optimizing Hormonal Responses for Maximum Muscularity and Definition
Parrillo Performance Products
(800) 344-3404
Part II: The Insulin-Glucagon Axis and Control of Nutrient Partitioning In Part I of this series we began our discussion of endocrine physiology. I explained that hormones play a central role in nutrient partitioning. But what is nutrient partitioning? This is the process of determining whether the food you eat ends up as muscle or fat or just gets burned for energy. The hormones chiefly responsible for this are insulin, glucagon, growth hormone, thyroid hormone, cortisol and epinephrine (adrenaline). In addition, testosterone, aldosterone and prostaglandin E1 may also play a role. If this sounds more like a boring medical lecture than an article about bodybuilding, consider the following:
1. Muscle growth and fat loss are controlled almost entirely by these hormones. (Have I got your attention now?) Youíre probably asking yourself, “But I thought this was determined by diet and exercise?” Yes, diet and exercise do determine muscle growth and fat loss, but these effects are mediated by hormones. Your diet and exercise habits set up a “hormonal environment” inside your body which determines if nutrients will be stored in the lean compartment or the fat compartment. This is how nutrient partitioning works. Does this mean that if someone injects growth hormone and insulin he can get lean and muscular without having to exercise? No, it doesnít work that way. Exercise is still required, for reasons weíll explain in Part III of this series.
2. If two groups of rats are fed and exercised the same, they weigh the same, just as you would expect. If one group is injected with insulin, however, that group becomes very fat (1,2). Furthermore, if another group is injected with glucagon, those rats lose weight [fat] (2). These hormones, insulin and glucagon, are perhaps the most important factors in determining body composition.
3. The composition of your diet (the amount of protein, carbohydrate and fat) seems to be as important as its caloric content in determining whether or not it will make you fat (1). If your metabolic rate is around 2,000 calories a day, two thousand calories from pizza will tend to make you fat. But 2,000 calories from chicken, rice and broccoli will tend to make you lean. Why? Because different foods have different effects on your bodyís hormones which control energy usage and fat storage.
4. Over 90% of people who lose weight by caloric restriction return to their original weight within two years (1). This is because there is a weight regulating center in your hypothalamus which tries to maintain a constant body weight. (Remember from last month that the hypothalamus and pituitary gland together represent the master endocrine gland of the body, controlling all of your hormonal responses.) It works like a “fat thermostat” by controlling your hunger level and your bodyís metabolic rate (its rate of energy expenditure). These effects are mediated by the nervous system and by hormones and enzymes involved in fat metabolism. If you want to change your body weight, or your body composition, you have to change the set point. The ratio of insulin to glucagon is perhaps the most important determinant of the set point (2) and weíll teach you how to control it in this article.
5. We all know examples of overweight people who starve themselves on 1,000 calorie a day, only to remain fat. We also know that some bodybuilders eat 6,000 to 8,000 calories a day and are extremely lean and muscular. How can this be? Obese people are very rarely overweight because they overeat, but rather because the way they eat and their lack of exercise raise the set point and act to channel calories to fat stores (1). The bodybuilders have learned how to channel their calories to the lean compartment and to minimize fat stores.
This is what nutrient partitioning is all about. At Parrillo Performance weíve been teaching people how to do it 
for years. (We were doing it before it was in, as they say.) We’ve had great success helping amateur and professional bodybuilders climb the ranks, and non-bodybuilders all over the country have used the same approach to lose weight permanently.
So how do you get control of your hormones and use this information to be a better bodybuilder? By careful control of your diet and exercise habits. The most important hormones involved in muscle growth are growth hormone (whose effect is largely mediated by the paracrine hormone IGF1), insulin and testosterone (3). The most important hormones in fat loss are insulin (lack of insulin, that is), epinephrine, growth hormone, glucagon, thyroid hormone and cortisol (3). Most of these can be controlled by diet and exercise and will fall within optimal levels if you follow our nutrition and training guidelines.
The best place to start in explaining these hormones is with insulin and glucagon. As mentioned earlier, these hormones are among the most potent determiners of fat storage and fat loss. Luckily for us, the levels of these hormones are entirely determined by diet, so we can control over them by carefully regulating what we eat. Insulin and glucagon are both produced by the pancreas, but have exactly opposite effects. Their chief concern is the regulation of blood sugar (glucose) levels. Your brain requires a constant supply of glucose for fuel, so the blood glucose level is tightly regulated to make sure the brain never runs out of gas.
When you eat carbohydrates they are digested and absorbed by the small intestine and transported directly to the liver via the portal vein. Essentially, all of the carbohydrate you eat is converted to glucose by the liver before being released into the bloodstream. After a meal your blood glucose level rises as carbohydrates are released. This rise in blood sugar triggers a release of insulin from the pancreas. Insulin is required to help move glucose into cells by a process called “facilitate diffusion.” Once inside cells, the glucose is burned for energy or stored as glycogen. Everything is fine so far. The problem arises when carbohydrates are released into the bloodstream too fast. This causes too much insulin to be released. When insulin levels get too high, some of the carbohydrate is converted to fat instead of being stored as glycogen. Also, if insulin levels get too high this actually causes too much sugar to be moved into cells. This results in “hypoglycemia,” which means low blood sugar. If your blood sugar is too low you feel very tired. Simple sugars cause your blood sugar level to spike, then paradoxically to decrease to a lower level than before (because of insulin over-release).
This is why the rate of digestion of your meals is important. On the Parrillo diet you stay away from foods containing simple sugars (sweets, fruit, dairy products) and refined carbohydrates (bread and pasta) because these are released into the bloodstream too fast, causing too much insulin to be released. This channels calories to fat storesóthe opposite nutrient partitioning we want. These foods also have the effect of raising the set pointóthe amount of fat your hypothalamus programs your body to store (1).
Combining protein and fibrous carbs with your starches, and avoiding simple and refined carbohydrates, slows the release of glucose into the bloodstream resulting in a lower, but longer, insulin release. This gives you a uniform energy level and channels calories toward muscle and away from fat.
In summary, the most important role of insulin is to regulate blood glucose levels. It does this by moving 
glucose into cells after a meal. It also increases the use of glucose for energy and increases glycogen stores. Too much insulin has the effect of promoting fat storage.
Glucagon is another hormone secreted by the pancreas, but it has the opposite effect of insulin. An increase in blood sugar triggers a release of insulin but inhibits glucagon release. Glucagon is released several hours after a meal when blood sugar levels drop. Glucagon has the effect of reducing glucose for energy and stimulating breakdown of body fat and the use of fat for energy. Glucagon also stimulates the glycogen breakdown. The net result of glucagon is to raise the glucose levels back to normal and to signal the body to begin using fat for energy since itís running low on carbs. This is how the insulin-glucagon axis acts to regulate blood sugar levels. Insulin decreases blood sugar by moving glucose into the cells, stimulating glucose burning for energy and increasing glycogen storage. Glucagon acts to increase blood glucose levels by stimulating glycogen breakdown, stimulating glucose synthesis (by a process know as gluconeogenesis) and by shifting the metabolism from carb-burning to fat-burning.
This is why you have to eat relatively more carbohydrates during the growth season and reduce carbs during the pre-contest diet. Insulin is an anabolic hormone, acting to stimulate growth. Glucagon acts to stimulate fat loss. The insulin to glucagon ratio is determined entirely by the ratio of carbohydrate to protein in your diet (3,4), so you can control it exactly. The insulin:glucagon ratio is believed to be one of the most important factors (if not the most important factor) in determining your set point (2). The precise levels of protein and carbohydrate to eat in order to optimize these hormones to maximize muscle growth or fat loss are described in detail in the Parrillo Performance Nutrition Manual. First, you want to meet your protein requirement by eating 1.0 to 1.5 grams of protein per body of body weight per day. Next, limit fat calories to 5% of your total daily caloric intake. Last, make up the remainder of your calories with a combination of carbs and CapTri. For weight loss, you generally want to limit carb:protein ratio to 1.0:1.5 and use more CapTri. For muscle gain you will want to increase the carb:protein ratio as well as increasing total calories.
Of course, there is considerable biochemical variation among individuals. Hi-Protein Powder and Pro-Carb Powder are very useful tools for dialing in your own bodyís optimal insulin:glucagon ratio. To gain lean body mass, meet your bodyís protein requirement then slowly add in more Pro-Carb until you find the optimal caloric level and insulin level for your body to gain lean mass. To lose fat you want to decrease carbs while increasing protein and CapTri®. Hi-Proteinô and Pro-Carbô are a convenient way for you to experiment and find how to optimize your bodyís hormonal responses. Weíve all had the experience of going to the trouble of weighing our food and filling out our Diet Trac Sheets only to find out the numbers donít work out right and we have to do it all over again. Hi-Protein and Pro-Carb are perfect for adjusting your dietary intake from food to make your numbers work out right on your Diet Trac Sheets.
One last thing about insulin. In addition to it enhancing transport of glucose inside cells, it is also required for transport of certain amino acids into cells. These include the branched chain amino acids (3), and this is why it is important to take your Muscle-Amino Formula with meals and not on an empty stomach. It has been found that neither insulin nor growth hormone alone is sufficient to stimulate growth you have to have both of them together at the same time (3). This at least partly due to the fact that these two hormones act to transport different sets of amino acids inside cells, and you need all of the amino acids present at the same time in order for growth to occur (3).
How do insulin and glucagon exert their effects over carbohydrate and fat metabolism? By activating or inhibiting the key regulatory enzymes which carry out these processes (5). Insulin acts to increase enzymes involved in the conversion of glucose to energy and enzymes carrying out glycogen synthesis, and to inhibit the enzymes of glucose synthesis and glycogen breakdown. [For those of you technically inclined, this means that insulin increases the activity of glucokinase and phosphofructokinase, which increases glycolysis (the first stage in the conversion of glucose to energy). Insulin also decreases gluconeogenesisóthe synthesis of glucose from from amino acids. Insulin increases the activity of glycogen synthase, the key enzyme regulating glycogen synthesis, and inhibits phosphorylase A, the enzyme responsible for glycogen breakdown.]
Glucagon has the opposite effects. These two hormones act to stabilize blood sugar levelsóinsulin by decreasing blood sugar and glucagon by increasing blood sugar. These effects are brought about by exerting control over the enzymes regulating carbohydrate metabolism. Regarding fat metabolism, insulin acts to activate the two most important enzymes regulating fat synthesis and storage. Glucagon inhibits these same two enzymes. In addition, glucagon initiates a cascade of events resulting in mobilization of fatty acids from fat stores. The fats are then transported to the muscles and used for energy. This is why this information is important for bodybuilders.
[Again, for those of you attuned to strict biological terminology, glucagon decreases phosphofructokinase and glycogen synthase, which decrease glycolysis and glycogen synthesis, respectively. Glucagon also increases the activities of fructose-1,6-biphosphatase and phosphorylase, which increases gluconeogenesis and glycogenolysis, respectively.] [Regarding fat metabolism, insulin acts to stimulate aceytl-CoA carboxylase and lipoprotein lipase, the most important enzymes regulating fat synthesis and storage, respectively. Glucagon inhibits these same two enzymes. In addition, glucagon activates adenylate cyclase which initiates a cascade of events resulting in mobilization of fatty acids from fat stores. The fats are then transported to the muscles and used for energy.]
In summary, insulin acts to increase enzymes involved in the conversion of glucose synthesis, and to inhibit the enzymes glucose and glycogen breakdown. Glucagon has the opposite effects. These two hormones act to stabilize blood sugar levelsóinsulin by decreasing blood sugar and glucagon by increasing blood sugar. These effects are brought about by exerting control over the enzymes regulating carbohydrate metabolism.
By now you know that insulin is a powerful growth-promoting hormone ósome people consider it the most powerful anabolic hormone. Does this mean we want to overeat carbohydrates or eat simple sugars to get our insulin levels really high? No, obviously not. Although insulin is absolutely required for muscular growth since it transports certain amino acids inside cells, it is not very selective in its actions. It promotes growth of fat cells as well as muscle cells (3,5). When insulin levels get too high some of the carbs “spill over” into fat stores.
When dieting, do we want to go on a zero-carb diet to minimize insulin and maximize glucagon? No way. Under these conditions muscle growth is impossible because some of the amino acids cannot get inside cells (3). However, your body continues to undergo a process called “obligatory protein loss,” which is the process of disposing of worn out proteins. (Proteins are the machinery of the cell, and they get worn out like any other machine.) This amounts to the obligatory loss of proteins from the body at about the rate of 30 grams per day, during starvation (3). When consuming a normal diet, these worn out proteins are simply replaced, but this canít happen if the amino acids canít get inside cells. So if you want a sure way to lose lean mass, go on a zero-carb diet. During a zero-carb diet the body is in a very catabolic state, and breaks down proteins to supply amino acids which are converted to glucose, which the brain requires for fuel. This makes the problem even worse.
Of course you want to adjust your carb:protein ratio, but moderation is the key. Going to extremes is asking for disaster. People have actually died from zero-carb diets even while getting plenty of protein, because they lost so much protein from their heart muscle. In general, stick to the formula in the Nutrition Manual, as outlined above. That will put you real close to optimal. Experiment with Hi-Proteinô and Pro-Carbô to find the perfect ratio for you. Learning to control the insulin-glucagon axis is one of the most important aspects of nutrient partitioning, and it will take you a long way toward a top physique.
Parrillo Performance Products
(800) 344-3404
References
1. Remington DW, Fisher AG and Parent EA. How to Lower your Fat Thermostat. Vitality House International, Provo, 1983.
2. de Castro JM, Paullin SK and DeLugas GM. Insulin and glucagon as determinants of body weight set point and microregulation in rats. J. Comp. Physiol. Psychol. 92: 571-579, 1978.
3. Guyton AC. Textbook of Medical Physiology. WB Saunders, 1991.
4. Westphal, SA, Gannon MC and Nuttall FQ. Metabolic response to glucose ingested with various amounts of protein. Am. J. Clin. Nutr. 52: 267-272, 1990.
5. Mathews CK and van Holde KE. Biochemistry. Benjamin/Cummings Publishing Company, Redwood, 1990.
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