The world is experiencing an epidemic of obesity and its concomitant health problems. One implication is that the normally robust negative feedback system that controls energy homeostasis must be responding to different inputs than in the past. In this review we discuss the influence of gender on the efficacy of adiposity hormones as they interact with food intake control systems in the brain. Specifically, the levels of insulin and leptin in the blood are correlated with body fat, insulin being related mainly to visceral fat and ieptin to subcutaneous fat. Since females carry more fat subcutaneously and males carry more fat viscerally, leptin correlates better with total body fat in females and insulin correlates better in males. High visceral fat and plasma insulin are also risk factors for the complications of obesity, including type-2 diabetes, cardiovascular problems, and certain cancers, and these are more prevalent in males. Consistent with these systemic differences, the brains of females are more sensitive to the catabolic actions of low doses of leptin whereas the brains of males are more sensitive to the catabolic action of low doses of insulin. The implications of this are discussed.