High(er) Dose Fish Oil (3g EPA+DHA per Day), an Effective Thermogenic for Older Women - 187 kcal/Day Higher RMR

This study is different from the average "fish oil is good for you" study and that's both refreshing and revealing. Speaking of "fresh" you got a 50/50 chance you buy fresh, not rancid fish oil.

I am not exactly a fan of fish oil supplementation, but I am neither ignoring the few gems among the bazillion of "fish oil is good for you" papers. Samantha L. Logan's and Lawrence L. Spriet's latest paper in the open access journal PLOS|ONE looks as if it was one of those gems. A gem that suggests that 3g of DHA + EPA per day (2 g/d EPA, 1 g/d DHA, to be precise) will not just lower the triglyceride levels of community dwelling older, healthy women by 29%, but also (a) increase their lean mass by 4%, (b) boost their functional capacity by 7% and (c) bump up their resting metabolic rate by 14%, their energy expenditure during exercise by 10%, and the rate of fat oxidation during rest and low-intensity cycling by 19% and 27%, respectively.
What? Yep, now I got your attention, right? Well, the objective of the study was to evaluate the effect of fish oil (FO) supplementation in a cohort of healthy, community-dwelling older females. Now, in contrast to your average fish oil study, the scientists did not restrict themselves to measuring the effects on blood measures of insulin, glucose, c-reactive protein, and triglycerides, though. Their primary study outcomes included the effects on the subjects' metabolic rate and substrate oxidation at rest and during exercise as well as on body composition, strength and physical function.

For the study, twenty-four healthy females (66 ± 1 yr) were recruited and randomly assigned to receive either 3g/d of EPA and DHA or a placebo (PL, olive oil) for 12 wk. Exercise measurements
were taken before and after 12 wk of supplementation and resting metabolic measures were made before and at 6 and 12 wk of supplementation.

Figure 1: Relative changes in metabolic parameters at rest and during 30 min of exercise (Logan. 2015).

As you already know and can now see in Figure 1, the fish oil supplementation significantly increased the subjects' resting metabolic rates, energy expenditure during exercise and the rate of fat oxidation at rest and during exercise. What is kind of funny, though, is that the scientists either misreported the actual values or miscalculated the changes, because I used the data from their study to calculate the relative differences in Figure 1 and as you can easily see those are significantly different from the values reported in the introduction - values I copied directly from the abstract.
Now the reason I am not going to spend time to find out, whether I or the researchers have made a mistake is that the statistically significant increase in resting metabolic rate for example amounts to 7kcal per hour, if the actual value is 2-5% lower or higher that's absolutely irrelevant. Since the same can be said for the other values, I think we all should be able to cope with any potential deviation from the actual data in the following overview I've compiled based on the (hopefully accurate) data from the tables in the full text of the study graphically in Figure 2.

Figure 2: Graphical overview of the absolute increase in energy expenditure and fat oxidation (Logan. 2015).

In conjunction with the marginal, but significant increase in lean mass, which does by the way only partially explain the increase in energy expenditure, these changes are not just statistically, but practically relevant - that's something even I, as a fish oil critic, have to admit ;-)
References:

• Logan, Samantha Louise. Physical Activity and Nutrition as Modifiable Lifestyle Factors for Healthy Aging in Older Adults. Diss. The University of Guelph, 2013.