The effects of two hypocaloric diets on body weight (BW), percent body fat (%BF), lean body mass (LBM) and static muscular endurance were studied in college aged experienced male weightlifters for 7 days. Nineteen (X age = 20.6) volunteers were randomly assigned to one of three groups: control (n=5), High Protein/Moderate Carbohydrate - HP/MC (n=7) or Moderate Protein/High Carbohydrate - MP/HC (n=7). The two hypocaloric groups consumed 18 kcal/kg body weight for 7 days. The HP/MC group's diet contained 1.6 g/kg body weight/day of protein while the MP/HC group consumed 0.8 g/kg body weight/day of protein. Fat content of both diets was approximately equal so that carbohydrate content varied inversely with protein content. The control group was asked to follow a weight maintenance diet. All groups followed a similar supervised weight training regimen approximately 2 hours per day, six of the seven days of the study. Analysis of variance revealed that weight loss for the control group was not significant over the seven day experiment but that the two experimental groups showed a similar significant decrease in body weight of 3.6 kg for the HP/MC group and 4.0 kg for the MP/HC group. %BF of all subjects was significantly lower over the 7 day study using both skinfold measurements and hydrostatic weighing but there was no significant difference between the groups. LBM losses calculated from skinfold measurements were seen over time for all subjects and a significant interaction showed the 2 experimental groups to lose significantly more LBM over the 7 day study. LBM determined from hydrostatic weighing produced losses as well, but no differences were noted between the groups. All groups experienced quadricep endurance decrements over the 7 day study, but did not differ from each other. No significant changes were found for bicep endurance. It was concluded that neither the HP/MC diet nor the MP/HC diet was effective for maintaining LBM or quadricep endurance. However, both diets did produce significant losses in BW and %BF over the week long study. / M.S.