Ingestion of a lipid-rich meat matrix blunts the post-exercise increase of myofibrillar protein synthesis rates in healthy adults: A randomized controlled trial

Background: There is considerable variation in the anabolic action of ingesting protein-dense foods on the stimulation of postprandial myofibrillar protein synthesis rates (MPS) despite ingesting similar amounts of protein and essential amino acids (EAA). Objectives: To determine the effects of consuming high-fat pork (HFP), low-fat pork (LFP), or a carbohydrate control (CHO) on the MPS response. Methods: In a semi-crossover design, sixteen physically active adults (25 ± 5 y; 25.0 ± 2.3 kg·m-2; 12M, 4F) received primed-constant infusions of L-[ring-13C6]phenylalanine and performed an acute bout of resistance exercise. Following exercise, participants ingested either HFP (266 kcal, 20 g protein, 20.6 g fat), LFP (120 kcal, 20 g protein, 4.4 g fat), or CHO (266 kcal, 0 g protein, 0 g fat, 73.3 g carbohydrate). Repeated blood and muscle samples were collected at rest and throughout 0-5 h post-exercise recovery to measure plasma variables and MPS. Linear mixed-effects models with time and condition as fixed factors weused to detect differences. Results: Both HFP and LFP conditions increased MPS above post absorptive values (P = 0.028 and P < 0.001, respectively), with LFP eliciting a greater post exercise MPS (0.106 ± 0.026 %·h-1; [95% confidence interval (CI): 0.088, 0.118]) than HFP (0.072 ± 0.027 %·h-1; [95% CI: 0.057, 0.087]; P = 0.030) and CHO (0.056 ± 0.035 %/h-1; [95% CI: 0.41, 0.71]; P < 0.001). The absolute change in MPS from basal was significantly correlated with peak essential amino acid and leucine concentrations (r = 0.4638, P = 0.017; r = 0.4211, P = 0.032). Conclusions: LFP stimulated MPS more than HFP or CHO conditions. Our work demonstrated that other nutrients in the food matrix, beyond total ingested protein or EAAs, can impact the regulation of MPS in healthy adults.