An anthropological perspective on obesity considers both its evolutionary background and cross-cultural variation. It must explain three basic facts about obesity: gender dimorphism (women greater than men), an increase with modernization, and a positive association with socioeconomic status. Preindustrial diets varied in quality but shared a tendency to periodic shortages. Such shortages, particularly disadvantageous to women in their reproductive years, favored individuals who, for biological and cultural reasons, stored fat. Not surprisingly, the majority of the world's cultures had or have ideals of feminine beauty that include plumpness. This is consistent with the hypothesis that fat stores functioned as a cushion against food shortages during pregnancy and lactation. As obesity has increased, the traditional gap between males and females in its prevalence has narrowed. Under Western conditions of abundance, our biological tendency to regulate body weight at levels above our ideal cannot be easily controlled even with a complete reversal of the widespread cultural ideal of plumpness.