The authors looked for studies of the following types of commercial weight loss programs: nonmedical programs (Weight Watchers, Jenny Craig, and L A Weight Loss), very-low-calorie diet, medically based programs (Health Management Resources and OPTIFAST), and commercial Internet-based programs (eDiets.com). They also included 2 nonprofit self-help programs (Overeaters Anonymous and Take Off Pounds Sensibly). The authors chose these programs because information about them has been published. The authors looked for studies that included adults in the United States, had more than 10 participants, lasted more than 12 weeks, and examined the program under the same conditions as it is offered to the public. The authors collected information about each program, the studies that had been done, and weight loss achieved in the studies.