Omega-3 supplementation not effective for weight loss
MedWire News: Dietary supplementation with long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) during a weight loss program does not assist weight loss, report Australian researchers in the journal Obesity Research and Clinical Practice.
Studies in animals have consistently shown that supplementing the diet with n-3 PUFAs reduces body weight, say Irene Monroe and Manohar Garg from the University of Newcastle in New South Wales.
They therefore investigated whether n-3 PUFAs, combined with a reduced energy diet, facilitated weight loss in obese (body mass index 30-40 kg/m2) men and women aged between 18 and 60 years.
All participants (n=35) followed an energy reduced, portion controlled, healthy eating weight loss diet, comprising a daily intake of 5000 kJ for women and 6000 kJ for men, for 12 weeks.
Eighteen individuals were randomly assigned to receive six 1 g capsules of monounsaturated oil per day (placebo) while 17 received six 1 g capsules of n-3 PUFAs (fish oil) per day. Each fish oil capsule contained tuna oil comprising n-3 PUFAs 360 mg with docosahexaenoic acid (DHA, 270 mg) and eicosapentaenoic acid (EPA, 70 mg).
Fasting blood samples, anthropometric measurements, and 3-day food diaries were collected at baseline and at 12 weeks.
Monroe and Garg report that there was a greater than two-fold increase in plasma levels of both EPA and DHA after 12 weeks of supplementation with fish oil. This difference was highly significant from baseline, as was the difference in EPA and DHA levels between the two groups post-intervention, they say.
Despite this increase, there was no significant difference within and between the placebo and fish oil groups for weight reduction (3.37 and 4.35%, respectively) or fat mass reduction (8.95 and 9.76%).
In addition, no significant differences for inflammatory biomarkers or blood lipids within or between groups were observed, apart from triglycerides which were reduced by a significant 27% in the fish oil group.
These findings suggest that n-3 PUFAs may not contribute to loss of weight or fat mass in humans, write the authors. However, because n-3 PUFAs have been shown to reduce body weight in animals, they suggest that these findings could be attributed to dietary compliance in humans.
"It is easier to manage dietary compliance when working with animals compared to working with humans, particularly when faced with feelings of hunger on an energy restricted diet," say Munro and Garg. "Self-reporting of dietary compliance can be misleading both through under-reporting and over-reporting dietary intake."
They conclude that future studies should consider more effective management strategies to encourage dietary compliance.
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By Nikki Withers