A couple of weeks ago one of my blog posts focused on a study which suggests that getting adequate sleep can have beneficial effects on body composition. While the mechanism that may be responsible here is not known, I speculated that it might have something to do with cortisol – lack of sleep can cause levels of this stress hormone to rise, which in turn could lead to a tendency to increased muscle breakdown and enhanced fat deposition in the body.
The idea that cortisol might have something to do with body composition has come up again in another recent study. In this particular study, individuals were randomised to take either 4 grams of safflower oil or 4 gram of fish oil (containing a total of 2400 mg of EPA and DHA) for a period of 6 weeks. At the end of the study, those taking the fish oil were found to have higher fat free mass (fat free mass in the body includes muscle) as well as lower fat mass. In addition, those taking the fish oil were found to have a tendency to lower levels of cortisol, although this was not statistically significant. The authors of this study do suggest that some ability to reduce cortisol levels might explain, at least in part, the ability of fish oil to improve body composition.
However, the authors of this study also consider other potential mechanisms. For example, they cite evidence which shows that omega-3 fats such as EPA and DHA have the ability to enhance fat ‘oxidation’ (metabolism) in the body, partly by facilitating the transfer of fat into the ‘mitochondria’ (the structures in the body’s cells responsible for turning fuel into energy). Omega-3 fats appear to stimulate fat burning too. Other work suggests that omega-3 fats can increase something called ‘thermogenesis’ (the production of heat in the body), as well as increase lean body mass (which would also tend give the metabolism a boost).
The authors of this study make mention of research which found that fish oil supplementation significantly reduced fat mass compared to supplementation with sunflower oil .
Fish oil has been linked with a variety of benefits for health, particularly with regard to cardiovascular disease prevention and enhanced brain function. Mounting evidence also links this particular type of fat with improvements in body composition, including lower levels of fat in the body.
1. Noreen EE, et al. Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults. Journal of the International Society of Sports Nutrition 2010, 7:31
2. Hill AM, et al. Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors. Am J Clin Nutr 2007;85:1267-1274