The main treatment forms of canine obesity are restriction diets and physical activity. In the present study, the effects of diet and exercise were analyzed in 30 obese female dogs, whose mean age was 7.1 yrs. These animals were divided in two groups: A (14 dogs treated with diet) and B (16 dogs treated with diet and exercise). Swimming was the physical activity of choice, for 20 min, twice a week. After six months, group A showed a higher mean weight reduction (15.7%) than group B (10.3%). On the other hand, body fat decrease was higher in group B (16%) than in group A (7.5%). Regarding blood biochemical analysis, group A presented a mean reduction of 33% in triglyceride levels, whereas group B had 35.8%. Cholesterol concentrations remained unaltered in group A and presented a decrease of 6.12% in group B. As for platelet count, group A presented a reduction of 28.9% and group B, 31.85%. Systolic blood pressure (SBP) decreased in 11.4% of dogs in group A and 13.5% in group B. We conclude that, although weight loss was higher in those dogs under diet, the diet and exercise combination was more efficient for the treatment of obesity, as it promoted a higher body fat loss, greater reduction in cholesterol levels and platelet count, as well as a significant decrease in SBP.