Exercise provides a means of increasing energy expenditure and may help adjust energy balance for weight loss and maintenance. At least 30 minutes a day of moderate intensity aerobic exercise per day is recommended for weight loss and maintenance but greater amounts appear to increase the magnitude of weight loss and maintenance. Resistance training has recently been shown to have positive effects on body composition but does not typically show significant decreases in weight. Regardless of weight loss, both aerobic exercise and resistance training have been shown to diminish risk factors for cardiovascular disease and diabetes. Since exercise is only effective if sustained, behavioural strategies such as self-monitoring, goal setting, social support, etc. are used to help individuals start and maintain exercise programs and show improved results compared to exercise programs without behavioural strategies. The available evidence indicates that exercise is an important component of weight loss and perhaps the best predictor of weight maintenance.