Unfortunately, diets rarely lead to permanent weight loss. An overview of commercial programs found that participants typically regained the weight they lost relatively quickly. Even in studies of medically supervised low-calorie diets, patients who succeeded in losing 15 to 25 percent of their body weight tended to be the exception, and many regained that weight fairly quickly.
Despite these trends, diets and commercial weight loss programs are still pervasive. Reasons for this include that the body quickly adapts to changes in caloric intake, weight loss programs tend to exaggerate their claims, and the media often depicts thinness as an essential part of attractiveness.