Obesity, particularly the abdominal phenotype, is associated with several reproductive disturbances. Whereas mechanisms by which obesity affect fertility are complex and still not completely understood, an important role appears to be played by the presence of a condition of functional hyperandrogenism and hyperinsulinaemia, which accompanies the insulin-resistant state. In women with the polycystic ovary syndrome, abdominal obesity may be co-responsible for the development of hyperandrogenism and associated chronic anovulation, through mechanisms primarily involving the insulin-mediated overstimulation of ovarian steroidogenesis and decreased sex hormone-binding globulin blood concentrations. By these mechanisms, obesity may also favour resistance to clomiphene and gonadotrophin-induced ovulation and reduce outcomes of IVF/ICSI procedures. Due to the beneficial effects of weight loss, lifestyle intervention programmes should represent the first-line approach in the treatment of infertile obese women. Insulin-sensitizing agents may add further benefits, particularly if administered in combination with hypocaloric dieting. Therefore, individualized pharmacological support aimed at favouring weight loss and improving insulin resistance should be widely extended in clinical practice in obese infertile patients. This may be beneficial even during pregnancy, thereby permitting favourable physiological delivery and healthy babies.