By Kathryn Doyle
(Reuters Health) - An updated review of 11 popular commercial diets found that only Jenny Craig and Weight Watchers show evidence for effective long-term weight loss.
Doctors might prioritize these options when talking to patients about commercial weight loss programs, at least until other types of diets, like Nutrisystem or SlimFast, have produced substantial evidence of consistent long-term results, the experts conclude.
"We're not necessarily excluding any of these programs," said lead author Dr. Kimberly Gudzune of The Johns Hopkins University School of Medicine in Baltimore, Maryland.
"We're trying to highlight the ones that do have the scientific evidence proving that they do work to lose weight and keep it off," Gudzune told Reuters Health by phone. "For others it is unclear, they may show short term weight loss with no long term results, or in the long term people start to begin to regain the weight."
Gudzune and her coauthors reviewed evidence in support of Weight Watchers, Jenny Craig, Nutrisystem, Health Management Resources, Medifast, OPTIFAST, Atkins, SlimFast, The Biggest Loser Club, eDiets and Lose It!
These programs emphasize dietary change or meal replacement and behavioral counseling or social support, but do not necessarily address physical activity.
Gudzune and her team selected 45 dietary trials, including 39 randomized controlled trials comparing the diets to a control group, completed between 2002 and 2014. Many were sponsored by the commercial programs themselves.
In six trials, by the one-year mark, people on Weight Watchers had lost almost 3% more of their initial body weight than did people in control groups. But they did not lose any more weight on average than people in comparison groups who had access to behavioral counseling consultations with providers, which would also encourage weight loss.
Three trials found that people on Jenny Craig had at least 4.9% greater weight loss maintained at the one-year point compared with people in a control group or those in a behavioral counseling group.
Three trials found that people using Nutritystem had at least 3.8% greater weight loss compared to control or counseling at the three-month point, but no trials continued a full year.
Similarly, programs which require very low calorie intake, like Health Management Resources, Medifast and OPTIFAST, did demonstrate more weight loss after three months than a control or counseling group, but effectiveness seemed to diminish beyond six months, the authors write in the Annals of Internal Medicine online April 6.
"While obesity continues to be a significant health risk in the U.S., our program provides the personal support and behavioral strategies that lead to healthy lifestyle change and can provide an effective solution for clinicians," Monty Sharma, CEO and president of Jenny Craig, told Reuters Health in a statement. "We are gratified that this independent study in a reputable journal has prioritized us as a weight loss solution for patient referrals and that the review showed that Jenny Craig is one of the most effective long-term weight loss solutions."
Trials of the Atkins diet found between 0.1% and 2.9% greater weight loss than counseling after one year, but potential harmful side effects and drop-out rates from the program were rarely reported, the authors write.
A representative for the Atkins diet disputes these conclusions.
"What the study does show is that any clinician recommending a weight loss program with a cost is going to help people lose weight but at a premium price," Colette Heimowitz, vice president of nutrition and education at Atkins Nutritionals, told Reuters Health in a statement. "Atkins is 100% free and its efficacy is proven with more than 80 independent clinical studies."
SlimFast trial results were mixed, and there was little evidence for weight outcomes for other programs.
Weight Watchers and Jenny Craig may be among the most effective programs because they are highly structured and often include in-person social support, according to Dr. Christina C. Wee of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston.
But weight loss with these programs is modest and likely below patients' expectations, which may make it harder for patients to stick with, and pay for, the programs long-term, Wee wrote in an editorial accompanying the new results.
"Medically we hope people achieve and sustain 3% to 5% weight loss from their starting weight," and people on Jenny Craig and Weight Watchers did meet that goal, Gudzune noted.
The trials in the review were not designed to pit the diets against each other and determine why one works better than another, she said, but the review should help doctors and patients discuss whether or not a commercial diet program is a good choice, and if so, which one to try.
In addition to evidence of effectiveness, people should consider varying costs and time commitments, she said.
"There is no one-size-fits-all solution for this," Gudzune said.