Two thirds of Americans are overweight, but anyone who’s tried to lose even a few pounds here and there knows what a struggle it can be. For assistance, millions of people turn to commercial weight-loss programs, like Jenny Craig or Nutrisystem, and even then, people find it difficult to lose weight and keep weight off. If this sounds familiar, take heart – a study by the Johns Hopkins School of Medicine found that few commercial diet programs have enough evidence to back their claims.
“Primary care doctors need to know what programs have rigorous trials showing that they work, but they haven’t had much evidence to rely on,” says Kimberly Gudzune, M.D., M.P.H., an assistant professor of medicine and a weight-loss specialist at the Johns Hopkins University School of Medicine. “Our review should give clinicians a better idea of what programs they might consider for their patients.”
The authors reviewed over 4,000 studies of commercial weight-loss programs, yet found that only about a dozen were scientifically reliable. Most weight-loss programs, they found, have spurious scientific evidence supporting their claim that people lose more weight with them than without. Most programs simply don’t have enough – or long enough – studies backing them to honestly make their claims.
Of 32 major commercial weight-loss programs marketed nationwide, only 11 have been rigorously studied in randomized controlled trials. The programs included three high-intensity programs:Weight Watchers, Jenny Craig and NutriSystem, which incorporate goal setting, self-monitoring, nutritional information and counseling. Three very-low-calorie meal replacement programs: HMR, Medifast and OPTIFAST were also included, along with five self-directed programs: Atkins, SlimFast, and the Internet-based Biggest Loser Club, eDiets and Lose It! Of those 11, only two were supported by gold-standard data showing that participants, on average, lost more weight after one year in these programs than people who were either dieting on their own: Weight Watchers and Jenny Craig. Even in those instances, results were “modest,” with participants losing 3-5% more weight than control groups.
The researchers cautioned that even the studies that met their standards weren’t perfect or uniform in their design or quality. Few ran for longer than 12 months, so it’s difficult to say how participants fared in the long run.
“Clinicians could consider referring patients who are overweight or obese to Weight Watchers or Jenny Craig. Other popular programs, such as NutriSystem, show promising weight-loss results, but additional studies evaluating long-term outcomes are needed,” the authors wrote.
The researchers noted that other programs aren’t necessarily bad, just unsupported by research. The low-carbohydrate Atkins diet, for instance, appears to have promising weight-loss figures for participants at the six and 12-month marks.