A comprehensive definition of the use of nutritional ergogenic aids is 'dietary manipulation to improve physical and sports performance'. Nutritional ergogenic aids are a growing market and are increasing in popularity and variety. There are a large number of products marketed as nutrititional ergogenic aids that also claim to assist in weight management, by virtue of a purported capability to affect some aspects of energy metabolism or, more often, body composition, increasing lean body (muscle) mass and/or reducing fat mass. These include protein and amino acid supplements, and combinations of ephedrine and caffeine, already presented in the preceding section. Caffeine has been proven to have ergogenic effects in a number of human studies, although the mechanism(s) behind these effects are largely unknown: the popular view is that caffeine, by virtue of its capability to inhibit cAMP phosphodiesterases, increases fat supply to the muscle, which in turn can increase fat oxidation, spare glycogen and thus extend exercise time, but there are other ways in which caffeine may impact positively on exercise performance, including effects on Na/K ATPase and intracellular calcium distribution in muscle cells (reviewed in references 75, 196 and 197). Evidence for ergogenic effects of Ephedra alkaloids - or of their combination with caffeine, beyond the effect brought about by the latter - is weak and insufficient,163,197,198 as is the evidence for ergogenic effects of protein and amino acid supplements.77199
Other supplements marketed both as ergogenic aids and weight-loss aids, by virtue of purported effects on body composition, are presented below.
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