Nutrition Calories and macronutrients Competitive bodybuilders traditionally follow two to four month diets in which calories are decreased and energy
expenditure is increased to become as lean as possible [2–6]. In addition to fat loss, muscle EPZ5676 mouse maintenance is of primary concern during this period. To this end, optimal caloric intakes, deficits and macronutrient combinations should be followed while matching the changing needs that occur during competition preparation. Caloric intake for competition To create weight loss, more energy must be expended than consumed. This can be accomplished by increasing caloric expenditure while reducing caloric intake. The size of this caloric deficit and the length of time it is maintained will determine how much weight is lost. Every pound of pure body fat that is metabolized yields approximately
3500 kcals, thus a daily caloric deficit of 500 kcals theoretically results in fat loss of approximately one pound per week if the weight loss comes entirely from body fat . However, a static mathematical model does not represent the dynamic physiological adaptations that occur in response to an imposed energy deficit . selleck chemical Metabolic adaptation to dieting has been studied in overweight populations and when observed, reductions in energy expenditure amount to as little as 79 kcal/d , to as much as 504 kcal/d beyond what is predicted from weight loss . Metabolic adaptations to bodybuilding contest preparation have not been studied however; non-overweight men who consumed 50% of their Thymidine kinase maintenance caloric intake for 24 weeks and lost one fourth of their body mass experienced a 40% reduction in their baseline energy expenditure. Of that 40% reduction 25% was due to weight loss, while metabolic adaptation accounted for the remaining 15% . Therefore, it should be expected that the caloric intake at which one begins their preparation will likely need to be adjusted over time as body mass decreases and metabolic adaptation occurs. A complete review of metabolic adaptation to dieting in athletes is beyond the
scope of this review. However, coaches and competitors are encouraged to read the recent review on this topic by Trexler et al.  which covers not only the physiology of metabolic adaptation, but also potential methods to click here mitigate its negative effects. In determining an appropriate caloric intake, it should be noted that the tissue lost during the course of an energy deficit is influenced by the size of the energy deficit. While greater deficits yield faster weight loss, the percentage of weight loss coming from lean body mass (LBM) tends to increase as the size of the deficit increases [7, 13–15]. In studies of weight loss rates, weekly losses of 1 kg compared to 0.5 kg over 4 weeks resulted in a 5% decrease in bench press strength and a 30% greater reduction in testosterone levels in strength training women . Weekly weight loss rates of 1.