Conjugated linoleic acid (CLA) leads to an improved muscle-fat ratio, reduces the fat proportion and at the same time preserves the fat free muscle mass. In addition, CLA can reduce the yoyo effect. We assume that CLA reduces the fat storage, decreases the number and the size of the fat cells and promotes the fat combustion. As muscles are clearly heavier than the body fat, CLA does not primarily generate a weight reduction, but more muscle mass in relation to the body fat!
A two years long study [1] in healthy, but overweight persons showed an up to 9% body fat reduction, a better maintain of the reduced weight and therefore a reduced yoyo effect. Another study with sportswomen showed a fat mass reduction of 8% with a body fat proportion decrease of about 6 % even without training [2]. The effect was even raised with training (-11% fat mass, -9% body fat)! The fat reduction effect of CLA was once more confirmed in a comparison of 18 studies in people about CLA and fat reduction [3].
As protection against free radicals, the anti-oxidative attributes of CLA are also interesting for sportspeople. The strength sportsmen also profit of a decreased catabolic effect and with it of a faster recovery of the musculature [4].
CLA is only found in food of animal origin. Nevertheless, modern animal feeding methods, diets with less meat and milk products as well as mainly vegetable fats have led to the situation that the content of CLA have decreased in the food. Meanwhile, the lowered amount of CLA in the food is also seen as a possible factor of the increasing overweight problems!

Literature - please have a look on the product details!