Utilization of protein at sub-maintenance energy intakes.

Adult rats fed a diet containing 14%, by weight, of protein displayed a negative N balance when energy intake was reduced to a value approximating basal metabolism. A positive N balance was induced, however, by raising the protein concentration in the diet, and N retention continued until body fat reserves were almost exhausted. These findings are in conflict with the widely-held view that N equilibrium can be achieved only when the need for energy is satisfied.