Obesity is a serious problem in the United States. More than 50% of adult Americans have body mass indices equal to or greater than 25--the new criteria for being overweight. US Government health organizations have recently issued clinical guidelines for the identification, evaluation, and treatment of obesity, and criteria for evaluating weight loss programs. Despite all this, overweight individuals often turn for guidance to weight loss books and programs promoted in the popular press rather than healthcare professionals. A review of some of the most popular diet programs reveals that they fall along a continuum from "anticarbohydrate" to "anti-fat." Several of these diets are discussed and evaluated based on the criteria proposed by obesity experts.