Obesity can impact on reproductive functions by causing hormonal imbalance and ovulatory dysfunction. Furthermore, obesity is associated with a range of adverse health consequences. There is a tight coupling between the reproductive system and energy balance. Obesity results from chronic imbalance between energy intake and energy expenditure, and therefore changes in energy expenditure impact on the reproductive system. Physical activity, through its effect on energy expenditure, plays an imperative role in maintaining energy balance and thus improving health. It is therefore recommended that weight loss is the best and the cheapest therapy for infertile obese women.