This study investigated the existence of difference of fat deposition and lipid metabolism in horses with different races and skills that were used for the same kind of sport. 20 Purebred Arabian and 20 Thoroughbred horses trained for flat race were evaluated. The analyses performed were body condition score, weight and blood collected for determination of triglycerides, total cholesterol and non-esterified fatty acids. Ultrasonography of the thickness of the subcutaneous fat layer was performed on the Longissimus dorsi muscle between the 17th and 18th rib, the thickness of the subcutaneous fat layer on the Gluteus medius muscle using the acetabulum as reference, and the cross section of the same muscle. Race-trained Arabian horses showed greater fat layer deposition in the Gluteus medius and Longissimus dorsei muscles than Thoroughbred horses. These facts indicate that there is a metabolic difference, besides the phenotype, between the races. They also indicate the need to study specific physical conditioning programs for each kind of race.