AENDO May 39/5

Forslund, Anders H., Antoine E. El-Khoury, Roger M. Olsson, Anders M. Sjödin, Leif Hambraeus, and Vernon R. Young. Effect of protein intake and physical activity on 24-h pattern and rate of macronutrient utilization. Am. J. Physiol. 276 (Endocrinol. Metab. 39): E964–E976, 1999.— Effects of moderate physical activity (90 min at 45–50% of maximal O2 uptake 2 times daily) and ‘‘high’’ (2.5 g protein·kg21 ·day21, n 5 6) or ‘‘normal’’ protein intake (1.0 g protein·kg21 ·day21, n 5 8) on the pattern and rate of 24-h macronutrient utilization in healthy adult men were compared after a diet-exercise-adjustment period of 6 days. Energy turnover (ET) was determined by indirect and direct (suit) calorimetry, and ‘‘protein oxidation’’ was determined by a 24-h continuous intravenous infusion of [1-13C]leucine. Subjects were in slight positive energy balance during both studies. Protein contributed to a higher (22 vs. 10%) and carbohydrate (CHO) a lower (33 vs. 58%) proportion of total 24-h ET on the highvs. normal-protein intake. The highest contribution of fat to ET was seen postexercise during fasting (73 and 61% of ET for high and normal, respectively). With the high-protein diet the subjects were in a positive protein (P , 0.001) and CHO balance (P , 0.05) and a negative fat balance (P , 0.05). The increased ET postexercise was not explained by increased rates of urea production and/or protein synthesis.