Purpose: Energy deficiency decreases muscle protein synthesis (MPS), possibly due to greater whole-body essential amino acid (EAA) requirements and reliance on energy stores. Whether energy deficit-induced anabolic resistance is overcome with non-nitrogenous supplemental energy or if increased energy as EAA is needed is unclear. We tested the effects of energy as EAA or carbohydrate, combined with an EAA-enriched whey protein, on postexercise MPS (%·h -1 ) and whole-body protein turnover (g protein·240 min -1 ).
Methods: Seventeen adults (mean ± SD; age: 26 ± 6 yr, body mass index: 25 ± 3 kg·m -2 ) completed a randomized, parallel study including two 5-d energy conditions (BAL; energy balance; daily energy requirements (DEF), -30% ± 3% energy requirements) separated by ≥7 d. Volunteers consumed EAA-enriched whey with added EAA (+EAA; 304 kcal, 56 g protein, 48 g EAA, 17 g carbohydrate, 2 g fat; n = 8) or added carbohydrate (+CHO; 311 kcal, 34 g protein, 24 g EAA, 40 g carbohydrate, 2 g fat; n = 9) following exercise. MPS and whole-body protein synthesis (PS), breakdown (PB), and net balance (NET; PS-PB) were estimated postexercise with isotope kinetics.
Results: MPS rates were greater in +EAA (0.083 ± 0.02) than +CHO (0.059 ± 0.01; P = 0.015) during daily energy requirements, but similar during BAL ( P = 0.45) and across energy conditions within treatments ( P = 0.056). PS rates were greater for +EAA (BAL, 117.9 ± 16.5; daily energy requirements, 110.3 ± 14.8) than +CHO (BAL, 81.6 ± 8.0; daily energy requirements, 83.8 ± 5.9 g protein·240 min -1 ; both P < 0.001) and greater during BAL than daily energy requirements in +EAA ( P = 0.045). PB rates were less in +EAA (8.0 ± 16.5) than +CHO (37.8 ± 7.6 g protein·240 min -1 ; P < 0.001), and NET was greater in +EAA (106.1 ± 6.3) than +CHO (44.8 ± 8.5 g protein·240 min -1 ; P < 0.001).
Conclusions: These data suggest that supplementing EAA-enriched whey protein with more energy as EAA, not carbohydrate, maintains postexercise MPS during energy deficit at rates comparable to those observed during energy balance.
Trial registration: ClinicalTrials.gov NCT04621175.
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