Influence of varying energy intake on nitrogen balance in men on two levels of protein intake.

Effect of changing energy levels of the diet at constant protein intakes on nitrogen balances in five young men were studied at two levels of protein--40 and 60 g. Nitrogen balance increased with increase in energy intake at both levels of protein. This was brought about primarily by a reduction in urinary nitrogen excretion. Energy levels at which nitrogen equilibrium was obtained were different for the two levels of protein intake. At 40 g protein intake the energy intake required for zero nitrogen balance was 2,249 kcal, while it was 2,066 kcal when the diet provided 60 g protein.