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Background The prevalence of obesity has increased dramatically. A direct comparison in the predisposition to obesity between males, premenopausal females, and postmenopausal females with various caloric intakes has not been made. To determine the effects of sex and ovarian hormones on the susceptibility to obesity, we conducted laboratory studies with mice. To eliminate confounders that can alter body weight gain, such as age and food consumption; we used mice with the same age and controlled the amount of calories they consumed. Methods We determined sex-specific susceptibility to obesity between male, non-ovariectomized female, and ovariectomized female mice. To compare susceptibility to gaining body weight between males and females, animals from each sex were exposed to either a 30% calorie-restricted, low-fat (5% fat), or high-fat (35% fat) diet regimen. To establish the role of ovarian hormones in weight gain, the ovaries were surgically removed from additional female mice, and then were exposed to the diets described above. Percent body fat and percent lean mass in the mice were determined by dual energy x-ray absorptiometry (DEXA). Results In all three diet categories, male mice had a greater propensity of gaining body weight than female mice. However, ovariectomy eliminated the protection of female mice to gaining weight; in fact, ovariectomized female mice mimicked male mice in their susceptibility to weight gain. In summary, results show that male mice are more likely to become obese than female mice and that the protection against obesity in female mice is eliminated by ovariectomy. Conclusion Understanding metabolic differences between males and females may allow the discovery of better preventive and treatment strategies for diseases associated with body weight such as cancer and cardiovascular disease.

Alcohol consumption promotes insulin sensitivity. In obesity, a decrease in body fat levels decreases the risk of developing insulin resistance; therefore, it is possible that alcohol improves insulin sensitivity by negatively affecting body fat. The aim of this study was to determine whether alcohol consumption promotes insulin sensitivity by reducing body fat levels in C57BL/6 male mice. We examined the effects of alcohol consumption on insulin sensitivity in male mice with three different body weight (BW) phenotypes. The BWs were induced by feeding the mice a 30% calorie-restricted (CR) regimen, a low-fat (LF) diet and a high-fat (HF) diet. The mice had free access to water or 20% ethanol in the drinking water. To determine the effects of the three different BW phenotypes and of alcohol on glucose regulation and insulin sensitivity, we performed the insulin tolerance test (ITT) and glucose tolerance test (GTT) on the mice. The effects of the diets and alcohol on body composition, percent body fat (% BF), percent lean mass and bone mineral density (BMD) were determined by dual-energy X-ray absorptiometry (DEXA). Data show that mice with the highest body fat levels (HF) were insulin resistant and glucose intolerant. In contrast, mice with the lowest body fat levels (CR) were the most insulin sensitive and cleared the injected endogenous glucose the fastest. Results show that alcohol did not affect GTT in any of the BW phenotypes. However, alcohol consumption promoted insulin sensitivity in mice consuming both the LF and HF diets. Alcohol consumption increased insulin sensitivity without affecting body fat levels, as body fat levels were similar in mice consuming the LF or HF diets and drinking either water or alcohol. Alcohol consumption promotes insulin sensitivity without affecting body fat levels in mice consuming LF and HF diets.