The potential effects of angiotensin II receptor blockers (ARBs) on adipose tissue biology and body weight are of considerable interest, because these agents are frequently used to treat hypertension in patients who are prone to visceral obesity, the metabolic syndrome, and diabetes. In rats fed a high-fat, high-carbohydrate diet, we compared the effects of 2 ARBs, telmisartan and valsartan, on body weight, food intake, energy expenditure, fat accumulation, fat cell size, and hepatic triglyceride levels. Telmisartan, but not valsartan, promoted increases in caloric expenditure and protected against dietary-induced weight gain. In the telmisartan-treated rats, absolute food intake, but not food intake adjusted for body weight, was lower than in valsartan-treated rats or controls. Telmisartan reduced the accumulation of visceral fat and decreased adipocyte size to a much greater extent than valsartan and was also associated with a significant reduction in hepatic triglyceride levels. Moreover, telmisartan, but not valsartan, increased the expression of both nuclear-encoded and mitochondrial-encoded genes in skeletal muscle known to play important roles in mitochondrial energy metabolism. Thus, in addition to a class effect of ARBs in modulating adipocyte size, these findings raise the possibility that certain molecules, like telmisartan, may have a particularly strong impact on fat cell volume and fat accumulation, as well as distinctive effects on energy metabolism, that may help protect against dietary-induced visceral obesity and weight gain.