In most people, body fat and weight remain remarkably constant over long periods despite fluctuations in food intake and activity level. The regulation of human energy balance is complex, involving numerous feedback loops to help control energy balance. In addition to short-term regulation of food intake, the body also regulates energy intake on a long-term basis. Along with leptin, the hormone insulin is also important in communicating adiposity to the brain. Resting metabolic rate represents a minimal rate of metabolism necessary to sustain life. Physical activity is a powerful metabolic stressor. Diet induced thermogenesis or the thermal effect of foods represents another important component of total daily energy expenditure. The interaction of heredity and environment may also explain why some people attain and maintain body weights higher than their set point. Setting reasonable and attainable goals is an important component of any successful weight management program. Physical activity is an important component of any well-designed weight management program.