One of the consequences of stress is abdominal fat-cell growth and loss of muscle mass—a scenario that leads to insulin resistance and obesity. This complex set of events orchestrated by the adrenal hormone cortisol, which is released in response to stress, is ultimately responsible for the fact that stress promotes weight gain. Cortisol is also a contributing factor in the blood glucose roller coaster so many suffer from. It has the exact opposite effect of insulin; cortisol raises blood sugar levels. Elevated cortisol levels are also associated with increased appetite, cravings for sugar and weight gain.
Fish Oil as a Weight-Loss Aid
The long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found in fish oil, have been shown to have a number of effects that indicate they are of value in improving metabolism and helping with weight loss. Studies show that animals who eat fish oil have significantly lower total body fat stores compared to those that have diets rich in other fatty acids. The exact mechanisms responsible for this phenomenon are not completely understood, but there are several possible explanations:
- EPA and DHA are very effective at suppressing the synthesis of lipids (fats) in the body.
- EPA and DHA increase the oxidation of lipids as a result of an increase in carnitine acyltransferase I (a substance that breaks down fats) activity.
- EPA can increase mitochondrial (cell energy) lipid oxidation.
- EPA and DHA can increase thermogenesis (heat production in the body).
- EPA and DHA can increase lean body mass.
New research is investigating whether EPA and DHA promote weight loss by lowering cortisol levels. Volunteers in a double-blind study were given either 4 grams a day of safflower oil or 4 grams a day of fish oil (1,600 mg of EPA and 800 mg of DHA) for six weeks. Results demonstrated that EPA/DHA significantly increased lean body mass and decreased fat mass. In addition, the volunteers who took EPA/DHA had a significant reduction in salivary cortisol. These results indicate that fish oil may exert an effect on central mechanisms in the body that control the release of cortisol.
Noreen EE , Sass MJ , Crowe ML, et al., Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. J Int Soc Sports Nutrition 2010, 7:31