Optimal dietary therapy for obese adolescents: comparison of protein plus glucose and protein plus fat

Nitrogen balance in six obese adolescent boys and three obese girls was studied during two nonconsecutive three-week dietary periods. Protein intake was based on an ideal body weight calculated from the measurement of total body water. The diets consisted of 1.5 gm meat protein/kg IBW/day plus 1.0 gm glucose/kg IBW/day, or an isonitrogenous diet made isocaloric with fat. Each dietary period was preceded by a controlled five-day diet designed to achieve weight maintenance. The first dietary period was followed by a one-month period of re-equilibration. The addition of carbohydrate to protein produced a significantly better cumulative nitrogen balance than P + F. Significant nitrogen losses persisted throughout the entire dietary period of P + F in three patients, but were observed in only one patient during P + G. Lymphopenia occurred in one subject on P + F but did not occur during P + G. Serum albumin concentrations were unchanged on both diets. Transferrin values decreased during P + F, but did not differ significantly from prediet levels during P + G. However, the observation of prolonged nitrogen losses in one subject on P + G and the limited experience with highly restrictive diets in obese adolescents emphasize that such diets must be used with caution and monitored carefully.