All study participants took regular doses of either omega-3-rich tuna oil or sunflower oil -- which is free of omega-3s -- but did not otherwise change their diets. Then, some of the participants were instructed to take a 45-minute walk or run three times a week. The exercising tuna oil group lost an average of 4 pounds while the exercising sunflower oil group, and both of the non-exercising groups, lost no weight at all.
Before the study, which was presented at the Congress of International Society for the Study of Fatty Acids and Lipids in Cairns, omega-3s -- like those found in grains, nuts and vegetables -- were known to help with cardiovascular problems, but their effect on weight loss was unknown.
"We were very surprised to see (tuna oil) was so effective, especially since these people were still eating whatever they wanted," said researcher Alison Hill. "It's pretty exciting because this implies the results would be even better if you did control diet and exercised more heavily."
Hill said that scientists are still not sure how omega-3 fatty acids work to assist weight loss, but they theorize that they "improve blood flow to exercising muscles and stimulate key enzymes to transport fat that needs to be used as fuel," an ability that is almost always impaired in overweight people, she said.
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