Ketogenesis refers to the creation of ketone in the liver that occurs when the body is desperate for energy due to low carbohydrate availability. The body has complex sensing mechanisms that respond to energy availability and body weight. For example, mTOR is a powerful signaling pathway that responds to changes in energy, nutrients, and growth factors. Nutrients and growth factors activate mTOR, which promotes muscle protein synthesis. Energy deprivation and ketosis suppresses the pathway. When the body is well fed and growing, mTOR is turned on; conversely, when energy (most strongly affected by glucose availability to the cell) is low, mTOR is turned off. Bodybuilders are most interested in activating mTOR in muscle, as well as turning it off in fat tissue. Unfortunately, the natural signals are generally not tissue-specific, meaning that what increases muscle-building also tends to promote fat gain; the opposite is also true, to increase fat loss, one risks increasing muscle loss. This may account for some degree of the association of muscle loss during dieting. Ketogenic diets restrict carbohydrate intake to 10 to 20 grams per day. Will following a ketogenic diet reduce muscle gains or promote muscle loss? Sadly, it appears this may be the case, particularly for drug-free bodybuilders. Ketogenic diets cause much lower blood insulin levels than normal. High levels of insulin activate the mTOR pathway and increases muscle growth. Studies in children on ketogenic diets have shown that they experience growth impairments in height and mass. Very low-carbohydrate diets increase muscle loss in drug-free bodybuilders. The loss of anabolic/anti-catabolic signaling from reduced insulin concentrations, along with increased thyroid hormone activity (a catabolic hormone), and reduced resting testosterone levels, combine to promote muscle loss and inhibit muscle gains. In recent professional bodybuilding shows, some athletes failed to reach former levels of competitiveness. No names will be mentioned out of respect for the efforts and frustration these men endured. Some of these athletes followed a ketogenic plan. Even for drug-enhanced bodybuilders, a ketogenic diet may produce a minor but significant deficit that can mean the difference between winning and losing. When dieting, people seek the fastest and most effective way to lose fat. For athletes and bodybuilders, ketogenic dieting is counterproductive. Muscle loss is too high a price to pay for reduced fat
Posted on: Tue, 28 Jan 2014 01:16:01 +0000
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