Evidence suggests that fish oils are beneficial to the health. One of the effects of fish oil consumption appears to be a decrease in systemic inflammation. This may explain the weight loss effects of fish oils as inflammation is associated with weight gain and obesity. Fish oils contain a number of fatty acids, but two that have been identified as contributory in the health effects of the oils are the omega 3 fatty acids eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)). In humans, both DHA and EPA accumulate in cell membranes following consumption, and here they acts as a labile supply of precursor molecules for a group of cell regulatory hormones including eicosanoids and docosanoids. Evidence suggests that EPA and DHA are converted to anti-inflammatory eicosanoids and docosanoids that are able to counter the pro-inflammatory effects of eicosanoids that are produced from another fatty acid belonging to the omega 6 family, called arachidonic acid (AA, C20:4 (n-6)).
A number of studies have looked at the cellular mechanisms by which fish oils may exert their beneficial effects. In this regard, much of the molecular work has been performed in cell culture and animals studies. For example, in one study1, researchers used cell culture and a mouse study to investigate the anti-inflammatory and anti-lipogenic effects of EPA. Mice were fed a low fat diet, a high fat diet, or a high fat diet supplemented with EPA for 11 weeks, or a high fat diet for 6 weeks and then a high fat diet supplemented with EPA for 5 weeks. Those mice consuming the EPA with the high fat diet had significant reductions in body fat compared to the high fat diet mice. Adiposity, adipocyte size and macrophage infiltration to the adipocytes (a pro-inflammatory condition) were significantly reduced in the EPA groups. However, no overall difference in weight was observed between the mice suggesting that the EPA groups may have had increases in lean mass to compensate for the weight lost through body fat reductions.
One interesting aspect of this study was that those mice fed the high fat diet followed by the high fat diet supplemented with EPA, demonstrated significantly lower mean adipocyte sizes and lower macrophage infiltration compared to the high fat only diet. This suggests that EPA is able to reverse the detrimental effects of a high fat diet including increases in adipocyte size and inflammatory markers. The cell culture studies conducted by the same group of researchers showed that addition of EPA to cultured cells significantly increased the mitochondrial activity of the cells and also increased the fat oxidation rates. Therefore it is suggested from the data that perhaps the EPA is able to increase the oxidation of fat, and this is the mechanisms by which the EPA in the diet of the mice was able to reduce the mean adipocyte size. This in turn might decrease the influx of macrophages to the tissue, which in turn decreases the inflammation observed. Therefore EPA may have anti-obesogenic effects, at least in mice.
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