The study found that at 12 months, Weight Watchers participants saw at least a 2.6 percent greater weight loss than those not on the plan, while Jenny Craig resulted in a 4.9 percent greater weight loss. That compares with 0.1 percent to 2.9 percent for Atkins during a similar time period, according to the study which was published in the Annals of Internal Medicine on Tuesday. Participants saw a greater weight loss at six months for very low calorie plans -- at least 4 percent for Medifast and OPTIFAST -- but that initial loss appeared to taper off in subsequent months.
Weight loss is a $2.5 billion and growing industry in the United States. With more than a third of U.S. adults obese and many more seeking to lose that extra 10 to 15 pounds, commercial weight loss programs -- which cost anywhere from around $50 to $700 a month -- have become increasingly popular tools. But physicians haven't had a lot of information to be able to recommend certain commercial programs, other diets or education and counseling.
A previously published study in the Journal of the American Medical Association in September 2014 found that low-carb and low-fat diets in branded weight loss programs -- those that are recommended through books, or in-person or online -- seem to work similarly well. "Despite potential biological mechanisms explaining why some popular diets should be better than others, recent reviews suggest that most diets are equally effective, a message very different from what the public hears in advertisements or expert pronouncements," the researchers wrote.