QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Todd, K. S. Articles by Calloway, D. H. Search for Related Content PubMed PubMed Citation Articles by Todd, K. S. Articles by Calloway, D. H.

Nitrogen Balance in Men with Adequate and Deficient Energy Intake at Three Levels of Work^1,2,

Department of Nutritional Sciences, University of California, Berkeley, Berkeley, CA 94720

Two studies were conducted to investigate the effects of mild exercise on nitrogen balance in men given diets supplying adequate or slightly limiting energy. In experiment A the diet supplied 91 mg N/kg body weight (0.57 g protein/kg, the FAO/WHO safe level of intake) as egg white; in experiment B the same source was used to provide the 1980 NRC-RDA for adult males, 128 mg N/kg body weight (0.8 g protein/kg). By adjusting energy intake and activity, periods of energy equilibrium and negative energy balance (-15%) were achieved at three levels of activity (X for exercise): no programmed work (0.85X), 1 hour of treadmill walking (1.0X) and 1 hour each of treadmill and cycle ergometry (1.15X). "True" nitrogen balance (TNbal) was more positive or less negative during periods of energy equilibrium as compared to those of energy deficit. This effect of energy balance on TNbal increased with physical activity. At the lower protein intake the mean difference in TNbal between the period of energy equilibrium and that of energy deficit at 1.0X was 0.19 g N/day (nonsignificant difference) and 0.54 g N/day at 1.15X. When protein intake was increased, the difference in TNbal between periods of equilibrium and deficit was significant at all levels of activity: 0.65 g N/day at 0.85X, 0.93 g N/day at 1.0X and 1.09 g N/day at 1.15X. Physical activity was anabolic when energy balance was maintained. In experiment A the addition of 1 hour of exercise (1.0X to 1.15X) spared 2.5 mg N/kg body weight; reducing activity by 1 hour (1.0X to 0.85X) cost 1.4 mg N/kg body weight. In experiment B, TNbal was more positive with increased activity (by 5.9 mg N/kg body weight) and more negative (by 11.5 mg N/kg body weight) when the men were sedentary. During periods of energy deficit, the anabolic effect of activity was also present, although less markedly. When activity increased from 1 to 2 hours in experiment A, TNbal improved by 2.1 mg N/kg body weight and in experiment B, by 3.5 mg N/kg body weight. Thus, circumstances of negative energy balance with adequate protein intake are better tolerated when the energy deficit is generated by physical activity than when it derives from reduced intake; the picture when protein intake is marginal requires further investigation.

KEY WORDS: • nitrogen balance • protein-energy interaction • work

¹ This investigation was supported in part by a grant from the National Institute of Arthritis, Diabetes and Kidney Diseases of the National Institutes of Health, no. AM-10202, and in part by State and Healch Funds allocated to California Agricultural Experiment Station, University of California, Berkeley.

² A preliminary report of part of this research was presented at the 65th Annual Meeting of the Federation of American Societies for Experimental Biology, Atlanta, Georgia, April 12–17, 1981. Butterfield, G. & Calloway, D. H. (1981) Protein utilization (PrU) in men fed inadequate energy at three levels of work. Fed. Proc. 40, 857 (abs. 3565).

³ Present address: Western Human Nutrition Research Center, U.S. Department of Agriculture, Agricultural Research Service, P.O. Box 29997, Presidio of San Francisco, CA 94129.

Manuscript received 22 March 1984.

This article has been cited by other articles:

				K. D. Hall Computational model of in vivo human energy metabolism during semistarvation and refeeding Am J Physiol Endocrinol Metab, July 1, 2006; 291(1): E23 - E37. [Abstract] [Full Text] [PDF]

				M. A. Pikosky, P. C. Gaine, W. F. Martin, K. C. Grabarz, A. A. Ferrando, R. R. Wolfe, and N. R. Rodriguez Aerobic Exercise Training Increases Skeletal Muscle Protein Turnover in Healthy Adults at Rest J. Nutr., February 1, 2006; 136(2): 379 - 383. [Abstract] [Full Text] [PDF]

				J. A. Bell, S. Fujita, E. Volpi, J. G. Cadenas, and B. B. Rasmussen Short-term insulin and nutritional energy provision do not stimulate muscle protein synthesis if blood amino acid availability decreases Am J Physiol Endocrinol Metab, December 1, 2005; 289(6): E999 - E1006. [Abstract] [Full Text] [PDF]

				K. D. Tipton, E. Borsheim, S. E. Wolf, A. P. Sanford, and R. R. Wolfe Acute response of net muscle protein balance reflects 24-h balance after exercise and amino acid ingestion Am J Physiol Endocrinol Metab, January 1, 2003; 284(1): E76 - E89. [Abstract] [Full Text] [PDF]