Meta-Analysis Says: Fish Oil Does Not Help You Lean Out! Plus: Why It's Still Worth Having Fatty Fish 1-2x/Week

SuppVersity readers know: Diet (and exercise) will make you lose weight. Supplements can only accelerate the process. However, it it really possible that fish oil does not even do that?

I guess those of you who are still taking it, will already have noticed that there is nothing to the whole hoopla about the "fat burning effects of DHA & EPA". A recent meta-analysis from the University of Sheffield in the United Kingdom does now confirm just that: The hypothesis that daily fish oil supplementation reduces body weight and BMI is not supported by scientific evidence -at least not in the overweight and obese study participants of the 9 studies that met the rigorous criteria of this meta-analysis.

The scientists had conducted a search of Web of Science, PubMed, Medline and Google Scholar for studies having the keywords ‘fish’, ‘fish oil’, ‘oily fish’, ‘omega three’, ‘omega-3’, ‘n-3’, ‘body weight’, ‘body composition’, ‘BMI’, ‘weight reduction’ or ‘weight loss’ in them.
From the query results, they filtered all papers that were not based on randomized controlled trials, had not compared the effect of fish oil supplementation with another (non-n-3) oil control [this is actually pretty interesting, because many trials simply throw the omega-3s on top of the regular diet and who can say that a spoon of olive oil would not have had similar, if not even more pronounced effects], had not used overweight or obese subjects and had not taken pre- and post-intervention measurements of body weight and BMI. Actually the fact that all of what they were left with were only 9 study is at least in my humble opinion an important result of this meta-analysis that tells you something about the "quality" of the omega-3 supplementation research out there.

Figure 1: Whether the participants received fish (FO) or placebo oil (PO) supplements did not make a difference; in fact, the results look (but aren't) slightly better in the placebo trial, usually (Harden. 2013)

The data I compiled in figure 1 gives you an overview of the results of the meta-analysis. It's not difficult to see that the remaining 9 studies clearly indicate that it is unrealistic to expect any direct effect on diet and/or diet + exercise induced weight loss.

---

Bottom line: While the weight loss effects of fish oils are in fact totally overblown, it should not be overlooked that their beneficial effects on the inflammatory processes that are particularly pronounced during phases of weight gain can ameliorate (but not blunt) many of the ill health effects that arise as a consequence of the steady increase of the adipose organ. I have previously discussed the possibility of becoming what scientists love to celebrate as "healthy obese" person by soothing the sickening inflammation that would otherwise increase with every pound of extra-weight. Now you would thus still end up being fat, but you would get rid of the fat much easier and most importantly without permanent damage to your health.

Figure 2: Effects of 2.8 g/day omega-3 supplement on reductions in weight, waist and hip width in severely obese women on very low carb, very  low fat low protein 550kcal diets (Kunesova. 2005)

Based on studies by Kunesova and Hlavaty from the years 2005 and 2008, respectively, n-3 supplementation can also offset the negative effects of crazy low carb + low energy diets, as they are used to treat severely obese men and women, they can keep the fatty acid composition of the serum lipids normal and help enhance body weight and more importantly body fat on low carb diets (as signified by the superior reduction in waist circumference; cf. figure 2) loss.

So, irrespective of whether you are trying to lose or gain weight, the 1-2x servings of fatty fish I would recommend as a preferred source of omega-3 fatty acids should remain a staple of your diet. If not for weight loss purposes, then for their beneficial effects on your overall health.


References:

• Harden CJ, et al. Preliminary meta-analysis of the effect of fish oil on body weight and body mass index in overweight and obese subjects does not support a link. Proceedings of the Nutrition Society(2013), 72 (OCE4), E283
• Hlavatý P, Kunesová M, Gojová M, Tvrzická E, Vecka M, Roubal P, Hill M, Hlavatá K, Kalousková P, Hainer V, Zák A, Drbohlav J. Change in fatty acid composition of serum lipids in obese females after short-term weight-reducing regimen with the addition of n-3 long chain polyunsaturated fatty acids in comparison to controls. Physiol Res. 2008;57 Suppl 1:S57-65.
• Kunesová M, Braunerová R, Hlavatý P, Tvrzická E, Stanková B, Skrha J, Hilgertová J, Hill M, Kopecký J, Wagenknecht M, Hainer V, Matoulek M, Parízková J, Zák A, Svacina S. 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. Physiol Res. 2006;55(1):63-72. Epub 2005 Apr 26.