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Years of studying various aspects of nutritional research have convinced me that it's important to supplement branched- chain amino acids (BCAAs) while dieting. In those on a lowered caloric intake, the primary amino acids extracted from muscle for energy are BCAAS and glutamine.
When that occurs, the muscle is in a catabolic state. It seems logical that supplementing these expendable aminos should provide at least a partial metabolic buffer against muscle catabolism. The BCAAs comprise three essential amino acids: leucine, isoleucine and valine. The
term "essential" means that these three must be supplied in the diet. Other aminos are termed "nonessential," which is a misnomer, since they are indeed essential to normal human metabolism. However, they are synthesized in the body. Branched-chain amino acids are unique in that
they are metabolized directly in muscle, in contrast to most other amino acids, which are metabolized in the liver, During exercise, the muscle enzyme that catalyzes BCAA reactions becomes more active, This is particularly true during prolonged exercise (over four hours), when
protein becomes an energy source. A recent study in the American Journal of Physiology (272:E233-E238, 1997) found that this BCAA-activating enzyme is also up-regulated during low- carbohydrate diets. Glutamine is another amino acid important to muscle function. It's found mostly
in muscle, where it constitutes 60% of the amino-acid content. Under catabolic conditions (or under the influence of cortisol, the adrenal catabolic hormone), glutamine exits the muscles because stress requires additional amounts of the amino acid for immune-cell activity.
Branched-chain aminos appear to contribute nitrogen "skeletons," which muscles use to synthesize glutamine. This is one way in which BCAAs may exert an anti catabolic effect in muscle. They are also used for gluconeogenesis in the liver, the process in which noncarbohydrates are converted into glucose for energy.
A recent study on the effects of various low-calorie diets underscores the vital role BCAA supplementation plays for athletes engaged in intense exercise and/or dieting. The research, published in the International Journal of Sports Medicine (18:47-55, 1997), involved 25 competitive wrestlers who restricted caloric intake for 19 days on the following diets: normal calories (as control), low calories, low calories/high protein, low calories/high. BCAAs and low calories/low protein. The findings clearly pointed to beneficial effects on body composition in the low-calorie/high-BCAA group. They showed greater weight loss and decrease in bodyfat percentages than the others. It was also noted that they lost fat primarily in the abdominal visceral area and the thighs. This is especially significant because abdominal visceral fat is closely associated with insulin resistance, which perpetuates bodyfat accretion.
Earlier studies showed that during catabolic states, such as starvation, plasma levels of BCAAs increase, indicating that proteins are being used as energy sources. Other research indicated that BCAAs can directly promote the synthesis of and prevent the breakdown of muscle protein without the presence of insulin. Indeed, the BCAA leucine is one of the most potent noncarbohydrate stimulators of insulin release. This is important since insulin is known to prevent muscle-protein breakdown. None of the participants in the International Journal of Sports Medicine investigation showed a decline in either anaerobic or aerobic exercise performance. This was attributed to the intake of sufficient carbohydrates (four and a half grams per kilogram of body weight. When the diets were compared with regard to body composition, those higher in protein proved most effective in. promoting weight reduction.
The study's authors attribute the fat losses evident in the lower-calorie diets to both decreased caloric intake and increased circulating growth hormone (OH) levels. The latter effect was especially noticeable in the diets high in protein and BCAAs.
This would seem to indicate 'that a higher protein intake may favor increased GH release during low-calorie diets, which in turn helps maintain lean tissue while fostering fat mobilization. The low-calorie diets also led to a decrease in active thyroid hormone (T3). This reduction is commonplace during dieting; it's a safeguard against the body cannibalizing its own tissues due to lack of calories. The authors of the report, however, presented no explanation for this decreased thyroid activity.