Zhang, Qinmin, and Michael G. Tordoff. No effect of dietary calcium on body weight of lean and obese mice and rats. Am J Physiol Regul Integr Comp Physiol 286: R669-R677, 2004. First published December 18, 2003 10.1152/ajpregu.00655.2003.-Recent epidemiological and animal studies have led to the hypothesis that low dietary calcium intakes contribute to obesity. Here, we evaluated whether calcium influenced the body weight of normal-weight and obese rodents. All experiments involved female C57BL/6J mice or SpragueDawley rats fed normal-or high-energy-density diets (3.8 or 4.7 kcal/g). Calcium intake was manipulated by allowing mice to drink sweetened 30 mM CaCl2 solution or feeding mice and rats diets differing in calcium content (0.2%, 0.6%, or 1.8% Ca 2ϩ ). Blood samples were taken from rats to confirm that the diets had their intended effects on metabolism. There were no effects of the calcium manipulations on energy intake, body weight, or carcass fat content and no simple relation between calciotropic hormones and body weight. One experiment found a significant decrease in body weight gain of lean and obese rats fed the 1.8% Ca 2ϩ diet, but we suspect that this was due to forced consumption of the unpalatable diet, reducing growth. These studies provide little support for the hypothesis that dietary calcium contributes to the etiology or maintenance of obesity.1,25-dihydroxyvitamin D3; parathyroid hormone; appetite; palatability; food intake THERE HAS BEEN CONSIDERABLE recent interest in the hypothesis that body fat stores are modulated by calcium intake (50, 55). Several epidemiological studies have found inverse correlations between calcium intakes and body weight (7, 10, 13, 17, 22-24, 30, 55). There are also reports that body weight is reduced during clinical trials involving calcium supplementation (10,15,29,55). A measure of the enthusiasm for this hypothesis is the number of reviews written about it (28,35,(48)(49)(50)52).Experimental support for an inverse relation between calcium intake and body weight has been derived from animal studies. There are several reports of reduced body weight gain in rats fed high-calcium diets relative to controls fed moderate levels of calcium (6,26,34,38,54). However, interest has been piqued recently by three studies showing that high dietary calcium reduces the obesity produced by feeding high-energy diets. Two studies (33, 55) involved groups of male aP2-agouti mice fed high-sucrose, high-lard diets that differed in the amount and source of calcium (i.e., 0.4% Ca 2ϩ from CaCO 3 , 1.2% Ca 2ϩ from CaCO 3 , 1.2% Ca 2ϩ from nonfat dry milk, or 2.4% Ca 2ϩ from nonfat dry milk). In one of these studies (33), food intakes of some groups were yoked to those of mice fed the 0.4% Ca 2ϩ diet. In both experiments, the high-calcium diets significantly reduced weight gain and fat pad mass, increased core body temperature, inhibited adipocyte fatty acid synthase expression, stimulated lipolysis, and reduced fasting plasma insulin and glucose concentrations. The third study (27...