Being either underweight or overweight can affect a womanʹs fertility. Irregular menstrual cycles, reduced spontaneous and assisted fertility and an increased risk of miscarriage are risks associated with obesity that are often overlooked. Excessive weight and central distribution of body fat are both related to an increased risk of normogonadotrophic anovulation. Weight loss can re-establish ovulation in obese anovulatory patients or improve their response to ovulation induction. However, even a small amount of weight loss (5%) may improve fertility. Men who are overweight or obese have significantly lower sperm counts than men of normal weight.