A new review of thousands of studies has found little evidence for the long-term benefit of commercial weight loss programs in the US – with a few exceptions.
John Hopkins researchers examined 4200 studies, but only 11 weight loss programs had been actually studied in randomised clinical trials – and in the few commercial programs tested this way for 12 months or more, participants achieved modest, sustained weight loss.
“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 Dr Kimberly Gudzune, 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.”
Participants in these trials lost, on average, more weight after a year than people who were dieting on their own, got printed health information, or received other forms of education and counselling sessions.
The weight loss was between 3 and 5% more than that achieved by the nonprogram participants.
The researchers cautioned that not all the studies in any category were equally well designed. And since they found few studies that ran 12 months or longer, it was often unclear how many participants sustained their weight loss over the long term.
Based on their analysis of the studies, the researchers found Jenny Craig and Weight Watchers were backed by clinical trials that lasted 12 months or longer and showed program participants had a greater weight loss than nonparticipants. “Given these findings,” the authors write, “it may be reasonable for clinicians to refer patients to Weight Watchers or Jenny Craig.”
Programs based on the Atkins diet — high in fat, low in carbohydrates — also helped people lose more weight at six months and 12 months than counseling alone. The approach “appears promising,” the authors write.