American Journal of Clinical Nutrition, Vol 42, 380-390, Copyright © 1985 by The American Society for Clinical Nutrition, Inc

ORIGINAL RESEARCH COMMUNICATIONS

Interrelationships of glucose and protein metabolism in obese adolescents during short-term hypocaloric dietary therapy

WH Dietz Jr and RR Wolfe

We studied the interrelationship of nitrogen balance (N-bal) and rates of glucose appearance (Ra), determined isotopically using U-13C- glucose, in 14 obese adolescents consuming either (1.5 g protein and 1.0 g glucose)/kg ideal body weight/day or an isonitrogenous diet made isocaloric with fat. Nitrogen balance was significantly (p less than .01) more positive with added glucose. Changes in plasma insulin, free fatty acids, or beta-hydroxybutyrate did not reliably predict N-bal. The Ra of glucose decreased significantly on both diets, but was significantly lower (p less than .001) after the addition of fat. A significant correlation of N-bal with Ra (r = 0.70, p less than .01) was observed only in the absence of dietary glucose. Insulin levels correlated with N-bal only in the presence of dietary glucose (r = 0.72, p less than .01). Nitrogen balance in the absence of dietary carbohydrate may be a consequence of net peripheral protein catabolism that is not directly mediated by the need for gluconeogenic precursors.