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Fish Oil for Fat Loss

Written by Tom Nikkola - Director of Nutrition & Weight Management

Most people would love the idea of keeping their lifestyle the same as it has been, taking a supplement and changing their body composition. There is no pill that will lead to six-pack abs, sculpted shoulders or tightly toned thighs, but a new study in the Journal of the International Society of Sports Nutrition shows that fish oil can be a big help.

Forty-four men and women supplemented with either four grams of safflower oil or four grams of fish oil. Those taking the fish oil decreased body fat and body fat percentage, increased lean body mass and saw a decrease in cortisol levels. Interestingly, the study participants were not instructed on diet or exercise. They were encouraged to keep their nutrition and exercise patterns the same as prior to the study.(1)

How does fish oil improve body composition?

The exact mechanisms in which fish oil decreases body fat mass were not part of this study. It is known the stress hormone cortisol, when it is elevated, increases the storage of body fat. In this study, cortisol levels were decreased along with body fat mass, so it’s possible the lower cortisol levels helped with decreases in body fat.

In addition, the omega-3 fatty acids found in fish oil have been shown to decrease inflammation. They are especially important for people who consume large amounts of omega-6 fatty acids, common in the standard American diet. Inflammation can be increased when people consume excessively high levels of omega-6 fatty acids found in vegetable oils, processed foods and conventionally raised meat and fish. Oftentimes, those who consume such a diet find tremendous benefit from supplementing with higher amounts of fish oil. As levels of inflammation decrease, the body may be better suited to handle blood-sugar and manage insulin.

Aside from reducing cortisol levels and inflammation, omega-3s can support fuel partitioning. The fatty acids can help the body to store more calories as glycogen (stored carbohydrate) rather than as fat. Though the body is able to store only limited amounts of carbohydrate as glycogen, omega-3 fatty acids’ ability to steer more nutrients toward glycogen storage steers them away from fat storage.(2)

Supplementing with omega-3 fish oil has also been shown to improve satiety, meaning people feel full longer.(3) The JISSN study did not have a diet for the participants to follow. They were told to eat as they had been and diet was not tracked over time. It’s possible, the people supplementing with omega-3 fish oil, ate less food without knowing it. A reduction in total food intake could also contribute to the decreased fat mass, but it would not explain the increase in lean body mass, also found in the study participants. If, in fact, people had fewer cravings, it’s possible the fish oil could have helped them make better nutrition choices without them consciously choosing different foods.

Finally, though it was not shown in this study, omega-3 fatty acids have been shown to raise metabolic rate as well. Though it is not a significant amount, the small increase in metabolic rate in combination with a decrease in cortisol, inflammation and an increase in glycogen storage can all lead to the decreased body fat levels associated with fish oil consumption.(4)

How much should I take?

The JISSN study used four grams of fish oil to produce the changes in body composition and decreases in cortisol. Each fish oil capsule usually contains 1-1.2 grams of fish oil. The concentration of DHA and EPA, the two most important omega-3 fatty acids, can vary significantly among different fish oil products. Look for one that has at least 50% of its fish oil coming from EPA and DHA. Some studies have shown that health benefits can be achieved with as little as two grams per day, others have used much higher levels.

As one’s diet improves, including consuming fewer processed foods and vegetable oils, and more pasture-raised, grass-fed or wild caught animal proteins, the need for high levels of fish oil can decrease. Those following a solid nutrition program, like in the Eat Well. Live Well. Nutrition Guide can likely get by with two to four grams of fish oil each day. Those who consume more processed foods and vegetable oils may need to take in more to balance the ratio of omega-6 to omega-3 fatty acids. If you’re unsure about the exact amount you should take, be sure to talk with a LifeTime Nutrition Coach.


In the battle against weight gain, there are a number of nutritional supplements to choose from. Some of the products designed for weight loss are only effective if everything else in one’s nutrition plan is spot on. With fish oil, people may find body composition benefits regardless of their current diet. That’s not to say simply taking fish oil will help an individual achieve a healthy weight, but it is clear that taking fish oil is beneficial even when the diet isn’t perfect. In addition, fish oil provides a number of other health benefits, which many weight loss supplements do not provide, such as supporting heart health, decreasing triglycerides, reducing joint pain and other benefits. Along with a high-quality multivitamin, fish oil is important whether you are a performance athlete, someone trying to lose weight, or just an individual looking to optimize health and live as long as possible. That’s why a high-quality multivitamin and omega-3 fish oil should help build the foundation of almost every individual’s nutrition plan. Talk to a Fitness Professional or Nutrition Coach to find out how much you should use and what kind to take.


  1. Noreen E, Sass MJ, Crowe ML, Pabon VA, Brandauer J, Averill LK. Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. JISSN. 2010;7:31
  2. Perricone, N. The Perricone Weight Loss Program. LE Magazine. November, 2005
  3. Parra D, Ramel A, Bandarra N, Kiely M, Martinez JA, Thorsdottir I. A diet rich in long chain omega-3 fatty acids modulates satiety in overweight and obese volunteers during weight loss. Appetite. 2008;51(3):676-680.
  4. Couet C, Delarue P, Autoine JM, Lamisse F. Effect of dietary fish oil on body mass and basal fat oxidation in healthy adults. Int J Obes. 1997;21:637-643

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

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