Scientists have known for some time that diets rich in seafood were associated with better weight control.
For example, a study published in October of 2004 showed that a diet high in fish reduced both body weight and blood levels of leptin: a hormone that promotes storage of calories as body fat.
The finding that fish-rich diets suppress weight-gain-promoting leptin is important. But, as it turns out, the leptin-suppressing effect of fish may not fully explain its role in controlling weight.
The exciting results of a new study in mice show that EPA and DHA—the long-chain omega-3s abundant in salmon, sablefish, tuna, and sardines—likely account for a substantial part of the weight control benefits of fish.
In fact, people in search of "fat-burners” may need look no further than the fish in their refrigerators, or their bottle of omega-3 supplements.
How omega-3s affect weight gain
Czech researchers tested the effects of EPA and DHA from fish oil on mice and recorded these results:
- Weight gain resulting from a high-fat diet was reduced when EPA and DHA intake was increased from one percent to 12 percent of total dietary fats.
- Accumulation of adipose (fat-cell) tissue was reduced, especially in the abdominal region, where weight gain in humans is associated with higher risk of heart disease.
- Diets high in EPA and DHA improved metabolism of fat and glucose (sugar).
The scientists concluded that EPA and DHA reduce accumulation of body fat in the animals by limiting the increase in size and numbers of their bodies’ fat cells: increases that would otherwise result from diets lower in omega-3s relative to other dietary fats.
Lead researcher Morten Bryhn offered this explanation of the benefits of diets high in omega-3s:
"A diet rich in red meat and vegetable oils [as in the standard American diet] increases accumulation of fat in fat tissue because of a chronic disarray of genes responsible for handling fatty acids and carbohydrates. The number of fat cells increases, and turnover of carbohydrates into fat is facilitated. Genes are constantly programmed to a situation of starvation and they need to be reprogrammed. Omega-3 fatty acids from seafood seem to do exactly that."
Patient, holistic approach pays off
Dr. Bryhn noted that the process of reprogramming genes is slow, and that the weight-reducing results of increasing one’s intake of omega-3s (from fish or supplements) are not immediate.
He also offered these words of wisdom: "Weight control should be a combination of reduced intake of red meat, saturated fat and foods containing vegetable oils and carbohydrates; regular exercise; and increased intake of omega-3 fatty acids high in DHA." Well said!
- Bhryn M et al. Omega-3 PUFA of Marine Origin Limit Diet-Induced Obesity in Mice by Reducing Cellularity of Adipose Tissue. Lipids 2004 Dec;39:1177-1185.
- Mori TA, Burke V, Puddey IB, Shaw JE, Beilin LJ. Effect of fish diets and weight loss on serum leptin concentration in overweight, treated-hypertensive subjects. J Hypertens. 2004 Oct;22(10):1983-90.
- Ikemoto S, Takahashi M, Tsunoda N, Maruyama K, Itakura H, Ezaki O. High-fat diet-induced hyperglycemia and obesity in mice: differential effects of dietary oils. Metabolism. 1996 Dec;45(12):1539-46.