Conjugated linoleic acid (CLA) is highly found in fats from ruminants and it appears to favorably modify the body composition and cardiometabolic risk factors. The capacity of CLA to reduce the body fat levels as well as its benefic actions on glycemic profile, atherosclerosis and cancer has already been proved in experimental models. Furthermore, CLA supplementation may modulate the immune function, help re-synthetize of glycogen and potentiate the bone mineralization. CLA supplementation also could increase the lipolysis and reduce the accumulation of fatty acids on the adipose tissue; the putative mechanisms involved may be its action in reducing the lipase lipoprotein activity and to increase the carnitine-palmitoil-transferase-1 (CAT-1) activity, its interaction with PPARγ, and to raise the expression of UCP-1. Although studies made in human have shown some benefits of CLA supplementation as the weight loss, the results are still discordant. Moreover, some have shown adverse effects, such as negative effects on glucose metabolism and lipid profile. The purpose of this article is to review the available data regarding the benefits of CLA on the energetic metabolism and body composition, emphasizing action mechanisms.