The measures of body composition indicated that the HPLC group lost significantly more fat than group. Along with their greater absolute weight loss, however, they also lost significantly more lean body mass than the LF group, despite a significantly and substantially greater dietary protein intake. The literature is conflicting with respect to body composition changes in children on a so-called"protein sparing modified fast." Studies that have relied on skinfold measurements have reported preservation of lean body mass with a high protein, very low calorie diet(30-32). In contrast to our protocol, several of these interventions had a structured exercise component, which may have affected the impact of weight loss on lean body mass(31,32). Studies in adults have reported an additive effect of exercise and protein in the preservation of lean body mass during weight loss(21,33). Our data suggest that HPLC diet alone cannot be accurately termed a"protein sparing" regimen. The absence of significant changes in bone mineral density over the intervention for either group is reassuring. An increase in urinary calcium excretion and a small decrease in bone mineral content were reported during 8 weeks of a carbohydrate restricted diet in adolescents, but these changes were reversed with liberalization of carbohydrates. The absence of a comparison control group and the very small sample size limits the generalizability of those findings(6) Despite significantly