Fishy diet may cut hunger hormone

A fishy diet may well be beneficial to health

A study of African tribes found that the one with a fish-based diet had lower levels of a hormone which influences appetite.

It suggests that people eating a fish-rich diet may find it easier to control their appetite - and perhaps their weight.

The tribes came from neighbouring regions, and ate a diet with the same number of calories - but composed of different types of food.

One was predominantly fish-based, while the other ate a vegetarian diet.

Researchers, from the Mayo Clinic in Rochester, Minnesota, looked at the levels of a hormone called leptin in men and women.

This hormone is produced by fat cells, and its role, in people with normal weight, is to tell people when they have had enough food.

They do this by producing the feeling of "satiety", or fullness.

Obesity link

High levels of the hormone have been linked both with obesity and a higher risk of heart disease.

This is possibly because as people gain weight, they need to produce more of the hormone to get the same effect.

We don't know if the findings will apply to a semi-overweight, urban-dwelling, North American population

Professor Virend Somers, Mayo Clinic

The researchers found that, on average, the fish-eating men had leptin levels of 2.5 nanograms per millilitre of blood, and the women 5.0ng/ml.

The vegetarian tribe men had an average reading of 11.2ng/ml and the women 11.8ng/ml.

The researchers said that the readings for women were particularly significant, as normally, women have higher leptin levels than men - which was not the case when women from the fish-eating tribe were compared with vegetarians.

However, the findings do not prove that reducing leptin levels can improve cardiovascular health.

Professor Virend Somers, from the Mayo Clinic, said: "We speculate that fish diet may change the relationship between leptin and body fat and somehow make the body more sensitive to the leptin message.

"However, this study only describes an association."

He said that the process might also work differently in Caucasians compared with Africans.

"We don't know if the findings will apply to a semi-overweight, urban-dwelling, North American population."

He said that fish consumption was low in most US diets, and that he would not recommend a wholesale dietary change on the basis of this study.