Effect of protein intake and physical activity on 24-h pattern and rate of macronutrient utilization

Am J Physiol. 1999 May;276(5):E964-76. doi: 10.1152/ajpendo.1999.276.5.E964.


Effects of moderate physical activity (90 min at 45-50% of maximal O2 uptake 2 times daily) and "high" (2.5 g protein. kg-1. day-1, n = 6) or "normal" protein intake (1.0 g protein. kg-1. day-1, n = 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 high- vs. 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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Calorimetry
  • Calorimetry, Indirect
  • Carbon Isotopes
  • Dietary Carbohydrates / administration & dosage
  • Dietary Carbohydrates / metabolism
  • Dietary Proteins / administration & dosage*
  • Dietary Proteins / metabolism
  • Energy Metabolism*
  • Exercise / physiology*
  • Fasting
  • Humans
  • Leucine
  • Male
  • Oxidation-Reduction
  • Oxygen Consumption
  • Proteins / metabolism*
  • Urea / metabolism


  • Carbon Isotopes
  • Dietary Carbohydrates
  • Dietary Proteins
  • Proteins
  • Urea
  • Leucine