Increased blood levels of the omega-3 fatty acids EPA and DHA is linked to lower incidence of obesity, suggesting a role for fish oils in weight management.
New findings reported in the British Journal of Nutrition indicate that overweight and obese people have blood levels of omega-3 fatty acids almost 1 per cent lower than people with a healthy weight.
“Our findings suggest that n-3 PUFA may play an important role in weight status and abdominal adiposity,” wrote the researchers, led by Professor Monohar Garg from the University of Newcastle, and president elect of the Nutrition Society of Australia.
Previous studies have implicated omega-3 in protective benefits against obesity, and the new study adds to this small but growing body of evidence. A considerable number of studies already support the benefits of the omega-3 fatty acids eicosapentaenoic acid (EPA, C20:5 n-3) and docosahexaenoic acid (DHA, C22:6 n-3) for cardiovascular health, and cognitive health. Other areas of potential for the fatty acids include mood and behaviour, eye health, cancer risk reduction, and improved infant development.
“Previous studies involving children and adolescents have shown a negative correlation between adiposity and plasma omega-3 PUFA and DHA concentrations, but there appears to be a paucity of research in adults,” explained the researchers.
The researchers recruited 124 people of varying weights: 21 were classified as having a healthy weight, according to their body mass index (BMI); 40 were classed as overweight; and 63 were obese. The researchers note that people who consumed omega-3 supplements were excluded from their study.
Blood samples were taken after the subjects fasted for at least ten hours. Prof Garg and his co-workers recorded an inverse relationship between total omeg-3 blood levels, as well as blood levels of DHA and EPA, with BMI, the subject’s waist size, and their hip circumference.
Indeed, obese people had omega-3 levels of 4.53 per cent, compared to 5.25 per cent in their healthy-weight peers. When the researchers classed the people according to their omega-3 levels, and not by their weight, they again observed that increased omega-3 levels were associated with a healthier BMI, a smaller waist, and a lower hip size.
“[Other] studies, along with our observations, suggest that omega-3 PUFA supplementation may play an important role in preventing weight gain and improving weight loss when omega-3 PUFA are supplemented concomitantly with a structured weight-loss programme,” wrote the researchers.
Commenting on the potential mechanism, the Australia-based researchers noted that is was “biologically plausible” that omega-3 fatty acids may aid weight management. Results from animal studies, for example, suggested that omega-3s may increase the production of heat by burning energy (thermogenesis).
Another study suggested a role of omega-3s in boosting the feeling of fullness after a meal (postprandial satiety) during weight loss in both overweight and obese individuals. Such observations are linked to changes in levels of hunger hormones like ghrelin and leptin which impact on appetite, said the researchers.
“Thus, the idea that fish oil can regulate weight status via improved appetite control along with a subsequent reduction in energy intake is plausible and worthy of further investigation,” wrote Prof Garg and his co-workers.
It is not clear from the results of this study if the link is causal or mere correlation. “[The studies conducted to date] make the basis for conducting more intervention trials in adults examining the influence of dietary supplementation with omega-3 PUFA-rich fats/oils in assisting weight loss and weight maintenance,” they concluded.
Source: British Journal of Nutrition
Published online ahead of print, doi: 10.1017/S0007114509382173
“Plasma n-3 polyunsaturated fatty acids are negatively associated with obesity”
Authors: M. Micallef, I. Munro, M. Phang, M. Garg