Lack of effects of fish oil supplementation for 12 weeks on resting metabolic rate and substrate oxidation in healthy young men: A randomized controlled trial

Abstract

Fish oil (FO) has been shown to have beneficial effects in the body via incorporation into the membranes of many tissues. It has been proposed that omega-3 fatty acids in FO may increase whole body resting metabolic rate (RMR) and fatty acid (FA) oxidation in human subjects, but the results to date are equivocal. The purpose of this study was to investigate the effects of a 12 week FO supplementation period on RMR and substrate oxidation, in comparison to an olive oil (OO) control group, in young healthy males (n = 26; 22.8 ± 2.6 yr). Subjects were matched for age, RMR, physical activity, VO2max and body mass, and were randomly separated into a group supplemented with either OO (3 g/d) or FO containing 2 g/d eicosapentaenoic acid (EPA) and 1 g/d docosahexaenoic acid (DHA). Participants visited the lab for RMR and substrate oxidation measurements after an overnight fast (10–12 hr) at weeks 0, 6 and 12. Fasted blood samples were taken at baseline and after 12 weeks of supplementation. There were significant increases in the EPA (413%) and DHA (59%) levels in red blood cells after FO supplementation, with no change of these fatty acids in the OO group. RMR and substrate oxidation did not change after supplementation with OO or FO after 6 and 12 weeks. Since there was no effect of supplementation on metabolic measures, we pooled the two treatment groups to determine whether there was a seasonal effect on RMR and substrate oxidation. During the winter season, there was an increase in FA oxidation (36%) with a concomitant decrease (34%) in carbohydrate (CHO) oxidation (p < 0.01), with no change in RMR. These measures were unaffected during the summer season. In conclusion, FO supplementation had no effect on RMR and substrate oxidation in healthy young males. Resting FA oxidation was increased and CHO oxidation reduced over a 12 week period in the winter, with no change in RMR.Trial Registration: ClinicalTrials.gov NCT02092649

Resting metabolic rate and skeletal muscle SERCA and Na + /K + ATPase activities are not affected by fish oil supplementation in healthy older adults

“…After the 12‐week supplementation period, we observed decrease in RMR and fat oxidation, and no change in CHO oxidation, with both OO and FO. These results suggest that n‐3 PUFA supplementation had no effect on RMR and substrate oxidation, consistent with recent investigations which reported no change on RMR and substrate oxidation after n‐3 PUFA supplementation in healthy young individuals (Jannas‐Vela et al, 2017; Noreen et al, 2010), sedentary older adults (Lalia et al, 2017), overweight individuals (Kratz, Callahan, Yang, Matthys, & Weigle, 2009), and insulin resistant patients (Lalia et al, 2015). In contrast, a study by our research group in untrained older females ( n = 12; 60–76 years) showed a significant increase in RMR (14%) and fat oxidation (19%) following 12 weeks of FO supplementation (2 g/day EPA, 1 g/day DHA), while the OO control group reported no change on either RMR or substrate oxidation (Logan & Spriet, 2015).…”

“…While evidence is mounting to suggest that n‐3 PUFAs do not regulate whole‐body energy metabolism in humans, it is possible that the molecular changes affecting RMR after FO supplementation cannot be detected by the current methods of indirect calorimetry (Jannas‐Vela et al, 2017). Rodent work has shown that n‐3 PUFAs have the capacity to affect ATPase enzymes (Fajardo et al, 2015); however, to date, there are no studies in humans that have examined if n‐3 PUFAs regulate the expression and activities of SERCA and NKA pumps.…”

“…One female participant from each group was removed due to unreliable resting metabolic measurements. The variability for RMR and substrate oxidation measurement is 2%–4% and 15%–25%, respectively (Jannas‐Vela, Roke, Boville, Mutch, & Spriet, 2017).…”

Adaptive thermogenesis by dietary n-3 polyunsaturated fatty acids: Emerging evidence and mechanisms

“…In parallel with these results, the inclusion of fish or fish oil in randomized trials of weight-loss-diets offered increased weight loss in healthy humans [74, 75]. Most recently, Jannas-Vela et al reported an interesting study [76] that determined the BMR and substrate oxidation in young healthy males subjects after 12 weeks of fish oil supplementation (2g/d EPA, 1g/d DHA) in comparison to olive oil intake. The authors identified that fish oil intake increased fatty acid and carbohydrate oxidation in the winter season, but not in summer, regardless of RMR.…”

“…The authors identified that fish oil intake increased fatty acid and carbohydrate oxidation in the winter season, but not in summer, regardless of RMR. These results imply that fish oil-mediated thermogenic activation may require additional environmental stimuli, such as cold temperature [76]. In the same context, the effects of n-3 PUFA were augmented with exercise [77], another signaling factor to promote adaptive thermogenesis [78].…”