Fish Oil / Omega 3’s Part 1: Can Fish Oil Help the Pounds Swim Away?

Almost everyone knows about fish oil now, but is it really everything it’s cracked up to be? Many people say the omega 3s from fish oil help with building muscle, increasing strength, developing power, losing fat, lubricate joints, as well as a myriad of other beneficial health effects. Furthermore, most “experts” say that you should strive to have an omega 3 to omega 6 ratio of 1:1. Is this really the best goal for a bodybuilder?

This article will be the first of a series that will delve into these claims to better understand if they are all myths or if there is solid evidence to back them up. This first article will be reviewing the effects of fish oil on fat loss in humans.

Fat Loss

One of the primary reasons that people take fish oil is for their supposed ability to increase fat loss. There are even some individuals who recommend megadosing (30g or more) on fish oil for this purpose. Now, aside from the logical improbability of this advice (adding 30g of oil will be adding roughly 270 cals to your diet every day, assuming you don’t compensate for the added calories), let’s see what research has been done in this area.

At first sight, it seems that the research is mixed and inconclusive. There are studies supporting fish oil for weight loss [2,4,5,6], and there are studies that show that it doesn’t make any sort of difference [1,3]. What is the reason for the discrepancy? As we will soon see, it has to do with financial incentives due to source of funding for the study as well as the studies designs.

Let’s start with the studies that showed that fish oil helped with weight loss.

  • Couet et al. showed that “Dietary [fish oil] reduces body fat mass and stimulates lipid oxidation in healthy adults.”
  • Kunesová et al. showed that “…long chain n-3 [omega 3’s] PUFA enhance weight loss in obese females treated by VLCD [very low calorie diet]. Docosahexaenoate [DHA] (22:6n-3) seems to be the active component.”
  • Hill et al. supports the notion that “Increasing intake of n?3 FAs could be a useful adjunct to exercise programs aimed at improving body composition and decreasing cardiovascular disease risk.”
  • Noreen et al. had the conclusion that “6 wk of supplementation with FO significantly increased lean mass and decreased fat mass.”

If one were to cherry pick only these studies, it might seem to be a good idea to go drown yourself in fish oil and watch the pounds come off.

Not so fast.

There are some major limitations to the above studies that should make us be very cautious about their conclusions:

  •  Couet et al. showed a whopping weight loss of 0.88 kg in the fish oil group vs. 0.3 kg in the placebo group over a 3 week period. Nothing remarkable, especially since longer trials fail to see this weight loss benefit [3]. Furthermore, the short-term respiratory quotient they measured (a way to determine fat vs. carb oxidation) does not correlate with higher loss of fat in the long term.
  • Kunesová et al. had the obese participants on a very low calorie diet and the participants did no resistance training. Thus, the results might only be applicable to this population studied. Also, the effect size was small (7.55±1.77 kg in fish oil group vs 6.07±2.16 kg of weight loss in placebo). Furthermore, the participants only had around 40 g of protein per day and only 9g of fat per day. This is much lower than what most people would have while dieting. The low fat could have also made them deficient in essential fatty acids (which could be why the fish oil helped) and they might not have been deficient with a more usual amount of fat in their diet (and thus the benefit of fish oil might have diminished).
  • While Hill et al. did say that n-3’s (omega 3’s) could be a useful adjunct to exercise programs, this important facet might get overlooked. In fact, the fish oil group on it’s own didn’t have any effect on fat loss (see figure 1 below). A more important detail though is that the authors did not control for total caloric intake between groups! This seems quite astonishing, seeing as their goals was to measure weight loss. The fish oil group had 143.4 kcal less on average than the control group (sunflower oil was used as the control). Taking this into account, fish oil only had a 0.32 kg difference in weight in 12 weeks. This difference could obviously be attributable to error in reporting food intake. Thus, this study actually does not support the use of fish oil for fat loss – it supports the use of exercise for fat loss (though it seems that fish oil can possibly augment the effect of exercise)!FIGURE 6.
                            Figure 1: Effect of Fish oil vs. Sunflower Oil on fat loss with or without exercise (Hill et al., 2007)
  • Noreen et al. had quite a few limitations. There was no exercise program, so we don’t know how the results would have turned out in a more athletic population. There was no dietary control, so one group could have consumed less calories. Their use of air displacement plethysmography (ADP) is pretty good, but still has its problems, and since the weight of the groups did not change much, the outcome of the study is almost entirely at the mercy of the accuracy of this assessment. Taking into account the accuracy of the testing device and the amount of fat loss in 6 weeks (-0.5 ± 1.3 kg, pretty pathetic), this study is not a strong supporter of fish oil for fat loss.

Well, things look a little bit different now, don’t they? This is why anyone can “prove” almost anything they want to by citing abstracts of studies. When looking into the full text is when you can really get to the bottom of the matter.


Let’s now look at the two studies that are not in support of fish oil for fat loss:

  • Bortolotti et al. concluded that “[Fish oil] supplementation did not significantly alter energy metabolism and energy efficiency during exercise in healthy humans.”
  • DeFina et al. argue that “Omega-3 fatty acids were not effective as an adjunct for weight loss in this otherwise healthy, overweight population.”

Let’s see if there were any methodological issues or limitations with these two studies:

  • Bortolotti et al. had a study duration that lasted only 14 days. This is likely too short to see any benefit in terms of fat loss. Also, the exercise component could have blunted any effect of the fish oil; however, when most people diet they exercise too, so this is not really a limitation.
  • DeFina et al. had a methodological design that was actually pretty tight: it was a long study duration (24 weeks), included an exercise component, and used DXA for measuring body composition, which is considered the “gold standard” in this regard. Below you can see the results of the study (Table 1). As you can see, there was no difference detected between groups.


Table 1: Mean change in adiposity measures in the omega-3 supplement and placebo groups (DeFina et al., 2011)

So what conclusions can we take away from all this? Until more robust and well-designed research becomes available, we can only conclude that fish oil and omega 3’s likely exert either a very small or no benefit for fat loss unless perhaps you are severely inflamed (very obese) or on a very low calorie diet with hardly any fat in it. It is possible that fish oil might have more of an effect if an exercise component is combined (Hill et al., 2007), further research needs to be done in this area. Lastly, many of the people used in the above studies were not very physically fit or performed high intensity exercise regularly. These two factors can possibly change the conclusion. Nonetheless, the current evidence for fish oil to aid fat loss is weak at best, but when additional research  comes out, you’ll know where to find it!

In the next article of this series, I will be reviewing the effects of fish oil on muscle growth. Stay tuned!



For an interactive list of the studies, abstracts, and limitations discussed in this post, click here.



  1. Bortolotti, M., Tappy, L., & Schneiter, P. (2007). Fish oil supplementation does not alter energy efficiency in healthy males. Clinical Nutrition,26(2), 225-230. doi:10.1016/j.clnu.2006.11.006. Retrieved from
  2. Couet, C., Delarue, J., Ritz, P., Antoine, J. M., & Lamisse, F. (1997). Effect of dietary fish oil on body fat mass and basal fat oxidation in healthy adults. International Journal of Obesity and Related Metabolic Disorders: Journal of the International Association for the Study of Obesity, 21(8), 637–643.
  3. DeFina, L. F., Marcoux, L. G., Devers, S. M., Cleaver, J. P., & Willis, B. L. (2011). Effects of omega-3 supplementation in combination with diet and exercise on weight loss and body composition. The American Journal of Clinical Nutrition, 93(2), 455–462. doi:10.3945/ajcn.110.002741
  4. Hill, A. M., Buckley, J. D., Murphy, K. J., & Howe, P. R. (2007). Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. The American Journal of Clinical Nutrition, 85(5), 1267–1274.
  5. Kunesová, M., Braunerová, R., Hlavatý, P., Tvrzická, E., Stanková, B., Skrha, J., … Svacina, S. (2006). The influence of n-3 polyunsaturated fatty acids and very low calorie diet during a short-term weight reducing regimen on weight loss and serum fatty acid composition in severely obese women. Physiological Research / Academia Scientiarum Bohemoslovaca, 55(1), 63–72.
  6. Noreen, E. E., Sass, M. J., Crowe, M. L., Pabon, V. A., Brandauer, J., & Averill, L. K. (2010). Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. Journal of the International Society of Sports Nutrition, 7, 31. doi:10.1186/1550-2783-7-31