Variable effects of 12 weeks of omega-3 supplementation on resting skeletal muscle metabolism

Omega-3 supplementation has been purported to improve the function of several organs in the body, including reports of increased resting metabolic rate ( RMR ) and reliance on fat oxidation. However, the potential for omega-3s to modulate human skeletal muscle metabolism has received little attention. This study examined the effects of eicosapentaenoic acid ( EPA ) and docosahexaenoic acid ( DHA ) supplementation on whole-body RMR and the content of proteins involved in fat metabolism in human skeletal muscle. Recreationally active males supplemented with 3.0 g/day of EPA and DHA ( n = 21 ) or olive oil ( n = 9 ) for 12 weeks. Resting muscle biopsies were sampled in a subset of 10 subjects before ( pre ) and after ( post ) omega-3 supplementation. RMR significantly increased ( 5.3%, p = 0.040 ) following omega-3 supplementation ( Pre, 1.33 ±0.05; Post, 1.40 ±0.04 kcal/min ) with variable individual responses. When normalizing for body mass, this effect was lost ( 5.2%, p = 0.058 ). Omega-3s did not affect whole-body fat oxidation, and olive oil did not alter any parameter assessed. Omega-3 supplementation did not affect whole muscle, sarcolemmal, or mitochondrial FAT/CD36, FABPpm, FATP1 or FATP4 contents or mitochondrial electron chain and PDH proteins, but did increase the long form of UCP3 by 11%. In conclusion, supplementation with a high dose of omega-3s for 12 weeks increased RMR in a small and variable manner in a group of healthy young men. Omega-3 supplementation also had no effect on several proteins involved in skeletal muscle fat metabolism and did not cause mitochondrial biogenesis.