Undernutrition has a known and well recognized negative impact on reproductive hormones, and ultimately fertility. In contrast, much less is known regarding the potential effects of overnutrition on the same hormones. Epidemiological data suggest that overnutrition might have a deleterious impact as well on the fertile potential of affected women, but very little is known about the mechanisms implicated. Such knowledge may be of importance, given the increasing prevalence of overweight and obesity worldwide.