SUMMARYIn light of the widespread phenomena of diet failure and excessive dieting, this paper presents a theoretical economic analysis of the decision‐making process of weight‐loss dieting. The paper incorporates behavioral elements involved in the process of dieting: effort exerted in dieting, influence of social norms concerning body weight, time‐inconsistent present biased preferences, and a distinction between naiveté and sophistication. The model explains cyclic dieting and provides interesting insights on the extent of weight‐loss dieting. The extent of dieting is an increasing function of initial body weight and a decreasing function of the effort exerted in dieting and the strength of social norms concerning ideal weight. Income and diet strictness have an ambiguous effect. In addition, greater dieting efforts are not necessarily balanced against a slowdown in body metabolism or a higher initial body weight. Copyright © 2011 John Wiley & Sons, Ltd.