Increased Protein Maintains Nitrogen Balance during Exercise-Induced Energy Deficit

• Autores: Matthew A. Pikosky, Tracey J. Smith, Ann Grediagin, Carmen Castaneda Sceppa, Lauri Byerley, Ellen L. Glickman, Andrew J. Young
• Localización: Medicine & Science in Sports & exercise: Official Journal of the American College of Sports Medicine, ISSN 0195-9131, Vol. 40, Nº. 3, 2008, págs. 505-512
• Idioma: inglés
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• Resumen

  • 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[middle dot]d-1 increased energy expenditure via exercise (50-65% V[spacing dot above]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[middle dot]d-1 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-15N]tyrosine and a 4-h, primed, continuous infusion of L-[15N]phenylalanine and L-[ring-2H4]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