High Compared To Standard Essential Amino Acid Intakes Enhance Whole-Body Protein Balance During Energy Deficit

Abstract

BACKGROUND: The effects of energy deficit on postabsorptive, postprandial, and post-resistance exercise muscle protein synthesis are generally well described. However, few studies have assessed whole-body protein turnover responses to energy deficit and concomitant protein feeding after exercise, particularly after ingesting varying amounts of essential amino acids (EAA). Assessing the post-exercise whole-body protein kinetic response to EAA feeding during energy deficit may provide a critical indication of the potential protein requirements needed to prevent disruptions in whole-body protein balance induced by the metabolic stress of underfeeding. PURPOSE: Determine the effects of consuming varying EAA intakes on integrated whole-body protein turnover during energy deficit. METHODS: Nineteen males (mean ± SD; 23 ± 5y; 25.4 ± 2.7kg/m2) completed a randomized, double-blind crossover study consisting of two, 5d periods of controlled energy deficit (30 ± 4%), separated by a 14d washout. Whole-body protein synthesis (PS), breakdown (PB), and net protein balance (NET) were determined at rest and post-resistance exercise at the end of each energy deficit period using primed, constant infusions of 2H5-phenylalanine and 2H2-tyrosine. Drinks providing standard (0.10g/kg/meal, 7.87 ± 0.87 g) and high (0.30g/kg/meal, 23.5 ± 2.54 g) EAA amounts were consumed post-exercise. Whole-body protein turnover (g protein/180min) is expressed as the change between the postabsorptive, resting period and the postprandial, post-resistance exercise period. RESULTS: Stimulation of PS (3.6 ± 0.6 vs. 0.2 ± 0.5) and suppression of PB (-25.5 ± 1.2 vs. -9.8 ± 0.7) was greater for high than standard EAA (P < 0.05). The resulting NET was more positive for high (29.0 ± 0.9) than standard (10.0 ± 0.4) EAA (P < 0.05). CONCLUSION: These data demonstrate that higher EAA intake enhances net protein balance in response to the combined stress of exercise and energy deficit, largely by attenuating protein breakdown, suggesting higher protein meals are necessary to support whole-body protein balance during the metabolic stress of underfeeding. Supported by USAMRDC; authors’ views not official U.S. Army or DoD policy.