Stimulation of the alpha-receptors signals the cells to start storing more fat. However, when these receptors are blocked (i.e., by alpha-antagonists such as yohimbine), the fat storage process is averted. Some researchers suggest that supplementing yohimbine, in combination with exercise, can maximize fat loss by increasing lipolysis. Exercise stimulates beta-receptors on fat cells, resulting in fat being released and used for energy, and supplemental yohimbine, through its actions on alpha-receptors, may block the normal resynthesis of fat during recovery.
Research has demonstrated that supplementation of yohimbine in adults significantly elevated blood markers of fat metabolism and was further enhanced with the addition of exercise. In one study, highly trained men who supplemented 10 mg of yohimbine twice a day for 3 weeks experienced significantly greater fat loss than the placebo group. However, because alpha-receptors are present in the heart, arteries, and lungs, in addition to fat tissue, many side effects of yohimbine use may occur. Some of the most common side effects are feelings of panic, clumsiness, and confusion. Based on the available research, the current recommendations are 0.2 mg per kg of body weight per day in two equally divided doses. The field of sports nutrition is rapidly advancing, with new research providing evidence in support of, or contesting the use of, supplements to augment performance (see Table 9.2). Concomitantly, the use of supplements in athletics and performance has increased considerably in efforts to enhance training, strength adaptations, recovery, metabolism, and hydration, as well as to reduce fatigue and deter injury. While many advantageous supplements exist, an equal number of ineffective aids persist, many of which are highly marketed, leaving consumers with uncertainty and a cause for possible harm. This chapter outlines the more widely used supplements, evaluating the available human-related evidence and the true performance and physiological effects that may be observed. Guidelines for rational use are profiled throughout the chapter and illustrated in Table.
