Effects of reduced energy intake on protein utilization in obese children

Dietary treatment of pediatric obesity is a challenge given the need for adequate nutrients to support the maintenance of lean tissue and growth. The primary purpose of this investigation was to assess the effects of reduced energy intake on protein turnover in obese children aged 8 to 10 years. Following a 2-week baseline period, 16 subjects reduced energy intake during a 6-week intervention period. At baseline and following the intervention, 15N-glycine methodology was used to measure nitrogen flux (Q), protein synthesis (PS), protein breakdown (PB), and net turnover ([NET] PS - PB). Other criterion measures included resting metabolic rate (RMR), fat mass (FM), fat-free mass (FFM), urinary creatinine to height ratio (Cr:Ht), and nitrogen balance (NB). On average, subjects lost 2.2 +/- 0.3 kg, of which greater than 85% was FM. Decreased Q (P = .03) indicated downregulation of protein turnover in response to diet-induced weight loss. While PB did not change, NET declined slightly (P = .06) as a consequence of reduced PS (P = .03). Reductions in FFM (P = .09), Cr:Ht (P = .02), and NB (P = .03) accompanied alterations in protein turnover, but there was no change in the RMR. In conclusion, while short-term therapy promoted the loss of FM and did not compromise RMR, practitioners must be cautious when prescribing diets, given the observed changes in protein utilization and somatic protein status. Longitudinal studies are needed to further characterize the metabolic responses of obese children to long-term diet therapy.