[Carlyn Waffa is a senior at The University of North Carolina at Chapel Hill. She is majoring in Exercise and Sport Science, and a National Academy of Sports Medicine Certified Personal Trainer. She is currently an Athletic Development Intern at Athletic Lab.] An athlete's metabolism, or their physiological capacity to transform chemical energy in food (kcal) to other types of usable energy in the body, is an adaptable mechanism that adjusts based on substrate availability and imposed physical demands. In athletes, weight cycling is a common phenomenon. Just like a yo-yo oscillates up and down, an athlete's weight may go up and down in the same fashion, as an athlete's weight frequently fluctuates between "in-season" and "off-season" training schedules. Weight loss phases are achieved from a caloric deficit, which may be the result of increased exercise or caloric restriction or a combination of the two. Nonetheless, quick-fix, short-term methods of weight-loss are not employed without consequence. Recent research suggests a causal link between the number of times an athlete cyclically loses and regains weight and a higher percentage of body fat later in life (Saarni, 2006). Oscillating weight loss and gain wreaks havoc on an athlete's metabolism, and the success rate of long-term weight loss from yo-yo dieting is painfully low. In fact, while dieting may work for an athlete to "make weight" in the short term, cyclical weight loss and regain is detrimental to weight control in the long term and may even predispose an athlete to obesity later in life (Saarni, 2006). Dieting can create a caloric deficit, or a negative energy balance, within the body. This is a less-than ideal situation from a biological perspective, as the human body naturally strives to [...]