Hormones such as testosterone, growth hormone and insulin stimulate anabolic actions in muscle; that is, they promote muscular
growth. These processes involve either an increase in muscle enzymes that control the protein-synthesis rate or a decrease in
the normal catabolic rate. Anything that tips the scales in favor of an anabolic, or building, response, usually results in
increased muscular growth.
Other hormones, such as cortisol, promote muscle catabolism. The extent of this process is best appreciated when you realize that most of the muscle-building effects of anabolic steroids accrue from an interference with cortisol's catabolic effect on muscle. Thus, if the ratio between anabolic hormones, such as testosterone, and catabolic hormones, like cortisol, is elevated in favor of cortisol, you will lose muscle.
From a dietary standpoint, certain nutrients may aid muscular progress by inhibiting or even blocking cortisol's catabolic effects. Consuming sufficient protein can have this effect, particularly through ingestion of specific amino acids. Self-styled nutrition experts who often criticize bodybuilders for "excessive" protein consumption are apparently unaware of studies that point to the anticatabolic effects of a heightened protein intake.
Amino acids, which are the elemental form of proteins, also have potent effects in this regard. In fact, most of the research that has demonstrated the anticatabolic effects of amino acids has occurred under extreme catabolic conditions, such as those experienced by hospitalized burn patients.
Such amino acids or amino-acid combinations as glutamine, OKG and others appear to work at least partially by dousing the catabolic flames of cortisol.
Past studies involving animals have shown that dietary fats also play an important role in modifying hormone secretion. For example, consuming a meal rich in saturated fat can decrease testosterone levels by about 30% within two hours after a meal. A high blood level of free fatty acids inhibits the release of human growth hormone. Conversely, other types of fat, such as the omega-3 fats commonly found in certain fish, increase growth-hormone release.
The latter effect occurs through a modification of body chemicals called eicosanoids. The effect of food intake on these vital chemicals is the subject of intense research, as well as the best-selling Enter the Zone by Barry Sears, PhD. As Sears notes in his book, eicosanoids affect every hormone system in the body, and these chemicals are made from dietary fat.
A recent study published in the American Journal of Physiology (269:E1067-E1075, 1995) shows that by modifying cortisol metabolism in the body, certain dietary fats can increase cortisol levels. This, of course, wouldn't be desirable for those seeking increased muscular size and strength. Even more ironic, the type of fat most potent in this regard is the same fat suggested by Sears and others as being most beneficial to health!
To understand how fat affects cortisol, you should be aware that cortisol, like other hormones, does not circulate freely in the blood. Instead, it circulates bound to a protein. The protein that ferries cortisol in the blood is called eortico steroid binding globulin (CBS). Studies show that this protein binds 90% of the cortisol in blood. Only free, or unbound, cortisol, however, is active. Thus, anything that helps free cortisol from its binding protein increases cortisol activity.
The new study that examined the effects of dietary fat on cortisol activity discovered that two types of fat in particular were most potent in decreasing CBS and thereby increasing free cortisol levels. The fats were tallow (often used in fried foods), which has a 49% saturated fat content and, surprisingly, oleic acid, the main fatty acid in olive oil. Oleic acid is classified as a monounsaturated fat and is considered benign because of its neutral effects on eicosanoid synthesis and blood-cholesterol levels.
The study also showed that polyunsaturated fats, characterized by being liquid at room temperature, have little or no effect on CBS and cortisol. Significantly, monounsaturated fat is the variety suggested by Dr. Sears and others as the best type of fat to consume. Polyunsaturated fats appear to have little effect because of their comparatively rapid absorption rates. Again, the mechanism involves a decrease in CEG, which increases free cortisol levels.
Thus, you may want to temper your enthusiasm for mono- unsaturated fat, which to a certain extent may be considered a catabolic nutrient. Small amounts of these fats, however, are probably innocuous in this regard.