Bodybuilding sometimes lends itself to enthusiasts pushing their physiques to lean extremes. This can include an incredibly restricted diet. Since dieting is catabolic (meaning it leads to muscle breakdown), bodybuilders may find themselves shedding the weight and the muscle. The leaner these athletes become, the more the body turns to muscle to satisfy its energy needs. As the body searches for an energy source, it continually breaks down protein, eventually liberating muscles of amino acids for fuel. The consequence of this is that protein synthesis is decreased due to a reduced energy intake.
A thermogenic is a broad term for any supplement that the manufacturer claims will cause thermogenesis , resulting in increased body temperature, increased metabolic rate, and consequently an increased rate in the burning of body fat and weight loss. Until 2004 almost every product found in this supplement category comprised the " ECA stack ": ephedrine , caffeine and aspirin . However, on February 6, 2004 the Food and Drug Administration (FDA) banned the sale of ephedra and its alkaloid , ephedrine, for use in weight loss formulas. Several manufacturers replaced the ephedra component of the "ECA" stack with bitter orange or citrus aurantium (containing synephrine ) instead of the ephedrine.