HAMBURG A number of nutrionists are convinced that certain vegetable fats and oils can prevent weight gain. The fats, called medium-chain triglycerides (MCT) and found in coconut and palm oils, made dietary success possible, DPA quoted Professor Walter Feldheim, of Kiel University, at a presentation of a nutrition study in September in Hamburg as saying.

Feldheim's research team at Prague's Charles University, showed that volunteers could digest more calories in a diet rich in MCT without gaining weight. But Feldheim warned against exaggerated expectations: "Much more research is needed."

The German Nutrition Society (DGE) in Bonn expressed skepticism about the suitability of these "lightweight" fats for dieting purposes.

It believes that the current stand of research is not yet conclusive enough to justify its broader use in dieting plans.

Questioned by the German Press-Agency DPA, the DGE said that a mixed and balanced diet, consisting of wholemeal and low-fat foods and plenty of fruit and vegetables, is still important. MCTs are useful in the diets of convalescents and can also help remedy fat-absorption dysfunctions.

The Prague study was based on the diets of 35 women of normal weight aged between 19 and 24. Over a period of four weeks foods containing MCT was added to their normal diet. Normal foodstuffs such as margarine, oil, butter and other animal fats almost exclusively contain only long-chained triglycerides (LCT). Feldheim admits that since the volunteers were not supervised, the temptation to make false returns is naturally great.

One possible explanation for the positive effects of MCTs, say experts, could lie in the fact that energy needs increase when LCTs are exchanged for MCTs. The German Institute for Nutritional Medicine and Dieting (D.I.E.T.) refers to another study in Prague in 1994 which showed that the energy needs of volunteers increased to an average 135 kilocalories daily.