Effects of omega-3 supplementation in combination with diet and exercise on weight loss and body composition

Journal Title (Medline/Pubmed accepted abbreviation): Am J Clin Nutr
Year: 2011
Volume: 93
Page numbers: 455-462
doi (if applicable): 10.3945/ajcn.110.002741

Summary of Background and Research Design

Background:Omega-3 fatty acids may have a weight loss-enhancing benefit. Preclinical results in animal models suggest that omega-3 fatty acids promote weight loss through various mechanisms including increased fat oxidation, adiponectin, suppression of fat deposition, adipocyte apoptosis, and/or appetite suppression. However, results of clinical studies have been mixed, with some cancer studies showing a weight gain with omega-3 supplementation.

Hypothesis/purpose of study: The study evaluated whether the addition of omega-3 fatty acids to diet and exercise would increase weight loss over 6 months compared with placebo.

Subjects:The study included 128 sedentary (exercising < 20 min/day on ≤ 3 day/wk) adults 30 to 60 years of age and a body mass index (BMI) ≥ 26 and < 40 without serious comorbidities.

Experimental design:Single institution, placebo-controlled, randomized study

Treatments and protocol:Individuals were randomized to receive 5 omega-3 capsules (3 g eicosapentaenoic acid [EHA] + docosahexanoic acid [DHA][5:1] in a 60% concentration of 2,258 mg fish-oil concentrate and 1,400 mg omega-3 fatty acids [1,000 mg EPA, 200 mg DHA] per dose) or placebo (soybean and corn oil [1:1]). Capsules were ingested during 2 meals each day, half-way through each meal. Compliance was monitored. All participants received counseling for exercise (based on maximal oxygen consumption [VO2max]) and diet, and completed exercise and dietary logs. Fasting blood samples were collected and assayed for lipoprotein, chemistry panel, complete blood count, C-reactive protein, thyroid-stimulating hormone, and red blood cell essential fatty acid analyses. Body composition, BMI, resting metabolic rate, and stress test electrocardiogram responses were assessed at baseline and Week 24. The Food Craving Inventory (FCI) was completed at baseline and Weeks 4, 8, 12, 20, and 24.

Summary of research findings
  • 81 individuals completed the study, but 84 were analyzed
      – Baseline characteristics of the participants in each group were similar.
  • 5 participants had treatment-related gastrointestinal adverse events; 3 in the omage-3 group and 2 in the placebo group.
  • Both groups lost > 5% of body weight, BMI, body fat, and waist circumference, with no statistically significant differences between groups.
       – Resting metabolic rate was also similar between groups.
  • There were no significant differences between groups for changes from baseline in blood pressure, glucose, insulin, high-density lipoprotein, and triglycerides.
       – Triglycerides decreased > 20%.
       – Low-density lipoprotein rose slightly from baseline in the omega-3 group and decreased in the placebo group resulting in a significant difference at study end (P = .03).
  • Both groups had a decrease in caloric intake; no interaction effect was observed between groups.
  • The FCI showed decreased cravings in both groups, with no significant differences between groups.

Interpretation of findings/Key practice applications:

There was no weight reduction benefit or change in cardiovascular disease risk factors with the addition of omega-3 to diet and exercise in sedentary overweight/obese individuals compared with placebo. Previous studies have reported mixed results with omega-3 supplementation. However, study design and subject populations varied widely and cannot be easily compared. In the current population, comparable lifestyle and dietary changes were achieved and supplementation compliance was high in both the omega-3 and placebo groups. Therefore, any differences in weight loss attributable to the omega-3 supplementation would likely have been detected. However, the study was limited by a high withdrawal rate and lacked power to detect a statistically significant weight loss difference. Study retention was 63% at 6 months, which was comparable to other weight-loss studies. The study had 80% power to detect an absolute effect of ≥ 1.4 kg; however, the absolute difference observed in this study was only 0.61 kg. In addition, the study population was relatively healthy and without metabolic abnormalities, which may have masked potential metabolic benefits of omega-3, such as triglyceride reduction in individuals with hypertriglyceridemia. The study showed a lack of effect from omega-3 supplementation on weight loss in healthy obese individuals; however, the potential cardiovascular effects from decreased triglycerides during omega-3 supplementation were likely present.
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