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Does Taking Fish Oil Supplements Lead to Weight Gain?

author image Stephen Christensen
Stephen Christensen started writing health-related articles in 1976 and his work has appeared in diverse publications including professional journals, “Birds and Blooms” magazine, poetry anthologies and children's books. He received his medical degree from the University of Utah School of Medicine and completed a three-year residency in family medicine at McKay-Dee Hospital Center in Ogden, Utah.
Does Taking Fish Oil Supplements Lead to Weight Gain?
Fish oil capsules spilling from bottle Photo Credit: Hunterann/iStock/Getty Images

Fish oil supplements are a rich source of omega-3 fatty acids, specifically EPA and DHA. Because they confer a variety of health benefits, EPA and DHA have been the subjects of intense scientific scrutiny. Omega-3 fatty acids have been attributed with reducing your risk for heart disease, and they may exert beneficial effects on Alzheimer’s disease, rheumatoid arthritis, inflammatory bowel disease and a number of other chronic conditions. The role of omega-3s in weight management is less clear, and some people even wonder if fish oil supplements can cause weight gain.

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EPA and DHA are instrumental in a variety of metabolic processes in your body. They reduce inflammation by competing with other fatty acids for enzymes that synthesize inflammatory chemicals. In addition, omega-3 fatty acids are converted to protectins, resolvins, lipoxins and maresins, all of which actively reduce inflammation in your tissues. Omega-3s help to decrease your triglyceride levels, thereby reducing your risks for fatty liver, metabolic syndrome and type 2 diabetes. In fact, a prescription drug containing concentrated omega-3 esters is now available for treating markedly elevated triglyceride levels.


The American Heart Association recommends that Americans consume at least 500 mg of omega-3 fatty acids daily, either from oily fish or supplements. The metabolism of 1 g of fat produces 9 calories, so eating the recommended dose of omega-3s alone would confer 4.5 calories daily, an insignificant contribution to your total caloric intake. However, fish oil supplements contain other fats in addition to omega-3s. One serving of a fish oil supplement might contain 2.5 to 3 g of total fat, or 22.5 to 27 calories, the equivalent of less than 2 teaspoons of sugar.

Weight Loss

Due to their desirable effects, omega-3 fatty acids have been examined for their potential use in treating obesity. Several studies have alluded to a weight-loss benefit from taking fish oil supplements. However, the February 2011 issue of “The American Journal of Clinical Nutrition” demonstrated that omega-3 fatty acids were not an effective weight-loss aid in otherwise healthy overweight individuals. Thus, it is still unclear if omega-3 fatty acid supplementation could be useful for weight loss, but there is no evidence that fish oil consumption leads to weight gain.


The daily consumption of at least 500 mg of EPA and DHA from fish oil is associated with significant health benefits. Fish oil supplements have not been linked to weight gain; rather, there is some evidence, albeit inconsistent, that omega-3 fatty acids could help some people lose weight. When compared to your total daily intake, the additional calories obtained from a typical fish oil supplement are inconsequential.

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