Blunted Muscle Protein Synthetic Response To Feeding And Resistance Exercise In Obese Young Adults

Abstract

Obesity induces anabolic resistance of myofibrillar protein synthesis rates (MPS) to the ingestion of a protein-dense food in young adults. However, the effectiveness of acute resistance exercise before food ingestion to enhance the amino acid sensitivity of MPS with obesity has not been examined. PURPOSE: To compare the impact of resistance exercise on MPS responses to protein-dense food ingestion in normal-weight (NW) and obese (OB) young adults. METHODS: 7 NW (21±1y, BMI 21.9±0.5 kg/m2) and 7 OB (22±1y, BMI 35.7±2.3 kg/m2) men and women underwent primed continuous L-[ring-13C ]phenylalanine infusions coupled with blood and muscle biopsy collections to measure MPS at basal and fed-state of the exercise (EX) and non-exercise (CON) legs. Participants performed unilateral resistance exercise (4 sets × 10-12 repetitions) followed by the ingestion of 6 oz of lean pork loin (36 g protein; 4 g fat; 180 kcal). RESULTS: Total work performed during exercise was similar among groups (NW: 1610±164 kg; OB: 1888±154 kg, P=0.24). Plasma essential amino acid concentrations increased similarly after pork ingestion in both groups (time effect: P<0.05) with peak values at 2 h of the postprandial period. Basal MPS was similar between NW and OB groups (P>0.05). MPS was stimulated in the EX and CON legs after pork ingestion in both the NW (absolute change from basal: CON 0.027±0.008 %/h; EX 0.058±0.011 %/h) and OB groups (CON 0.027±0.006 %/h; EX 0.033±0.011 %/h; P<0.05). MPS was stimulated to a greater extent in the EX vs. CON legs in NW (P=0.02) but not OB group (P=0.26). CONCLUSION: Our results suggest that increased adiposity may attenuate the effectiveness of resistance exercise to augment the postprandial MPS response. Funding provided by the ACSM Foundation Doctoral Student Research Grant