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Med Sci Sports Exerc. 2008 Mar;40(3):505-12. doi: 10.1249/MSS.0b013e31815f6643.

Increased protein maintains nitrogen balance during exercise-induced energy deficit.

Author information

1
U.S. Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.

Abstract

PURPOSE:

This study examined how a high-protein diet affected nitrogen balance and protein turnover during an exercise-induced energy deficit.

METHODS:

Twenty-two men completed a 4-d (D1-4) baseline period (BL) of an energy balance diet while maintaining usual physical activity level, followed by 7 d (D5-11) of 1000 kcal.d increased energy expenditure via exercise (50-65% V O2peak). One group consumed 0.9 g of protein per kilogram per day and maintained energy balance throughout the 11-d intervention (BAL, N = 8). The other two groups consumed their BL energy intake throughout the 11 days, resulting in a 7-d, 1000-kcal.d energy deficit. These groups consumed either 0.9 g of protein per kilogram per day (DEF, N = 7) or 1.8 g of protein per kilogram per day (DEF-HP, N = 7). Mean nitrogen balance (NB), calculated per kilogram of fat-free mass (FFM), was determined for BL, days 5-8 (EX1), and days 9-11 (EX2). Whole-body protein turnover was derived from phenylalanine and tyrosine kinetics assessed while fasting at rest on days 4, 7, and 12, using a priming dose of L-[ring-N]tyrosine and a 4-h, primed, continuous infusion of L-[N]phenylalanine and L-[ring-H4]tyrosine.

RESULTS:

DEF experienced a decrease in NB from BL to EX 1 that was maintained in EX 2. No changes in NB occurred for BAL or DEF-HP over time. No within- or between-group differences were found over time for Phe flux (Qp), conversion rate of Phe to Tyr (Qpt), or the derived protein synthesis value (Sp).

CONCLUSION:

Increased dietary protein maintained NB during exercise-induced energy deficit, but this did not impact resting whole-body protein turnover.

PMID:
18379214
DOI:
10.1249/MSS.0b013e31815f6643
[Indexed for MEDLINE]

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