Fish Oil and Fat Loss
by Mike Roussell
Let's look at some of the studies that have recently displayed the effectiveness of fish oil in helping shed those nasty pounds. The first one comes from the International Journal of Obesity where they took 324 overweight and obese men and women and put them on a reduced calorie diet. (3) These people then received either nothing, fatty fish, lean fish, or fish oil capsules.
I should mention that the diets they were put on weren't very conducive to weight loss. Participants were consuming 50% of their calories from carbohydrates and only 20% of their calories from protein. They also weren't exercising — it was like the researchers were setting them up to fail!
Despite the odds, the men lost an average of 14 pounds, and the men that ate fish or took fish oil lost an extra 2 pounds. There was an added weight loss advantage even in the group of men that ate cod (non-fatty fish). However, the driving force behind this stumped the researchers.
One of the first studies to show the fat loss effects of fish oil was published back in 1997. The participants were put on a diet containing 50% calories from carbohydrates. Instead of supplementing with fish oil the whole time, 12 weeks into the study some of the participants were asked to replaced 6 grams of fat in their diet with 6 grams of fish oil for the remaining three weeks. (4)
The people who replaced fats in their diet with fish oil lost 2 pounds over three weeks while the non-fish oil group lost 0.7 pounds. That may not seem like a lot at first but you need to consider that these people didn't do anything different except for replacing fat in their diet with fish oil — they didn't exercise and they were on a high carbohydrate diet.
What's the take-home message here? These two studies suggest that even when people are put on high carbohydrate diets, fish oil supplementation can increase fat loss and fat oxidation (especially in men).
The most popular fish oil and weight loss study as of late was published in the American Journal of Clinical Nutrition. (5) Unlike the previous two studies we've looked at, this study used a fish oil supplement that contained high levels of DHA (much like Flameout).
In this all-male study, the participants were given either sunflower oil or DHA-rich fish oil. Some were instructed to exercise while others were not. The exercise component was walking at 75% of their maximum heart rate for 45 minutes, three times a week.
Regardless of the less-than-optimal program design, the fish oil and exercise people experienced decreases in body mass greater than any of the other groups combined. The authors noted, "Both FO supplementation and regular aerobic exercise reduced fat mass."
And here's some unpublished/unreleased info regarding this study, a T-Nation exclusive. One variable that the researchers measured but haven't yet reported on was heart rate. The fish oil group experienced a significant reduction in resting heart rate compared to the others not receiving fish oil.
Because their exercise goals were heart rate oriented (75% max heart rate), the fish oil group had to work harder to achieve their exercise goal. This is potentially one of the reasons that the fish oil group lost more weight.
How fish oil effects resting heart rate is also not fully understood; however, we know from cardiovascular research that increased consumption of EPA/DHA can change the electro-chemistry of your heart. This is why fish oil can help prevent sudden death from heart attacks. This is also probably the reason why fish oil can modulate resting heart rate.
Another way that fish oil mediates fat loss is through substrate utilization, as fish oil has been previously shown to increase fat utilization during exercise. Because we also saw a fat loss effect of fish oil independent of exercise in the first two studies, it looks like there are several mechanisms at work to boost fat loss — some exercise related, some not.
The exact mechanism in which fish oil potentates fat loss isn't completely understood. There seems to be both exercise and non-exercise pathways. Here are some potential ways that fish oil can help boost fat burning:
• DHA has been shown to prevent the conversion of pre-adipocytes to adipocytes and mediate pre-adipocyte death (kill 'em before they become immortal fat cells). (6)
• Fish oil has the ability to increase the clearance of chylomicrons and fats following a meal. This potentially can have a positive effect on substrate utilization. (7)
• Fish oil can "artificially" decrease heart rate thus increasing the level of exertion needed to reach desired intensity.
• Fish oil upregulates mitochondrial machinery and increases oxidation of fats within fat cells. (8, 9)
You may be wondering why improving insulin sensitivity isn't on the list? If you examine the broad range of studies that look at this, you'd see that there doesn't seem to be much of an effect (if any), especially in healthy people. Potentially there may be an insulin sensitizing effect in people with type II diabetes.