Studies have taken place in the US and in Norway that show that conjugated linoleic acid (CLA) helped overweight people lose fat but maintain the muscles in their bodies, in other words, it helped people shed fat without losing their body strength. It also improved the control of diabetes in adults.

CLA is a fatty acid found in many dairy products and beef. Animal studies have suggested that it also fights several types of cancer and the narrowing of arteries.

Results of the first human trials were presented to the annual meeting of the American Chemical Society in Washington DC.

The US trial took 6 months and eighty overweight people took part. Most people lost weight while dieting but put it back on when they stopped. For the ones who did not take CLA, the ratio of weight gained was 75 per cent fat to 25 per cent muscle - a typical balance for most people. However, for those who did take the supplement, the ratio was almost 50:50.

Study leaded Michael Pariza said: “That is very significant. This supplement could now prove to be useful in weight management. Our results also showed that the acid made it easier for people to stay on their diets.”