| Three weeks of caloric restriction alters protein metabolism in normal-weight, young men. | |
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MedLine Citation:
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PMID: 15870104 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The effects of prolonged caloric restriction (CR) on protein kinetics in lean subjects has not been investigated previously. The purpose of this study was to test the hypotheses that 21 days of CR in lean subjects would 1) result in significant losses of lean mass despite a suppression in leucine turnover and oxidation and 2) negatively impact exercise performance. Nine young, normal-weight men [23 +/- 5 y, 78.6 +/- 5.7 kg, peak oxygen consumption (Vo2 peak) 45.2 +/- 7.3 ml.kg(-1).min(-1), mean +/- SD] were underfed by 40% of the calories required to maintain body weight for 21 days and lost 3.8 +/- 0.3 kg body wt and 2.0 +/- 0.4 kg lean mass. Protein intake was kept at 1.2 g.kg(-1).day(-1). Leucine kinetics were measured using alpha-ketoisocaproic acid reciprocal pool model in the postabsorptive state during rest and 50 min of exercise (EX) at 50% of Vo2 peak). Body composition, basal metabolic rate (BMR), and exercise performance were measured throughout the intervention. At rest, leucine flux (approximately 131 micromol.kg(-1).h(-1)) and oxidation (R(ox); approximately 19 micromol.kg(-1).h(-1)) did not differ pre- and post-CR. During EX, leucine flux (129 +/- 6 vs. 121 +/- 6) and R(ox) (54 +/- 6 vs. 46 +/- 8) were lower after CR than they were pre-CR. Nitrogen balance was negative throughout the intervention ( approximately 3.0 g N/day), and BMR declined from 1,898 +/- 262 to 1,670 +/- 203 kcal/day. Aerobic performance (Vo2 peak, endurance cycling) was not impacted by CR, but arm flexion endurance decreased by 20%. In conclusion, 3 wk of caloric restriction reduced leucine flux and R(ox) during exercise in normal-weight young men. However, despite negative nitrogen balance and loss of lean mass, whole body exercise performance was well maintained in response to CR. |
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Authors:
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Anne L Friedlander; Barry Braun; Margaret Pollack; Jay R MacDonald; Charles S Fulco; Steve R Muza; Paul B Rock; Gregory C Henderson; Michael A Horning; George A Brooks; Andrew R Hoffman; Allen Cymerman |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. Date: 2005-05-03 |
Journal Detail:
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Title: American journal of physiology. Endocrinology and metabolism Volume: 289 ISSN: 0193-1849 ISO Abbreviation: Am. J. Physiol. Endocrinol. Metab. Publication Date: 2005 Sep |
Date Detail:
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Created Date: 2005-08-10 Completed Date: 2005-09-21 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 100901226 Medline TA: Am J Physiol Endocrinol Metab Country: United States |
Other Details:
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Languages: eng Pagination: E446-55 Citation Subset: IM |
Affiliation:
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Geriatric Research Education and Clinical Center and Research and Medical Services, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, USA. friedlan@stanford.edu |
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| MeSH Terms | |
Descriptor/Qualifier:
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Adolescent Adult Body Composition Body Weight Caloric Restriction* Calorimetry Carbon Isotopes / diagnostic use Energy Metabolism / physiology* Exercise / physiology* Humans Insulin / blood Leucine / metabolism Male Nitrogen / metabolism Proteins / metabolism* |
| Chemical | |
Reg. No./Substance:
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0/Carbon Isotopes; 0/Proteins; 11061-68-0/Insulin; 61-90-5/Leucine; 7727-37-9/Nitrogen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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