A summary of 39 scientific studies involving 11 popular diet plans singled out Weight Watchers and Jenny Craig as most effective.

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CHICAGO — Trying to slim down? Weight Watchers and Jenny Craig scored the best marks for effectiveness in a review of research on commercial diet programs, but many other plans just haven’t been studied enough to evaluate long-term results.

The two plans are among the most popular and had the best evidence that dieters could lose meaningful amounts of weight and keep it off for at least a year, the review authors said.

Pooling results from several studies, the researchers found that Weight Watchers dieters lost an average of at least 8 pounds and kept it off for at least 12 months versus about 15 pounds for those using the Jenny Craig plan.


Weight Watchers


Jenny Craig


Most participants remained overweight, with weight loss of between 3 percent and 5 percent of their initial weight — but that’s a range that doctors typically recommend to achieve healthful benefits including lower blood pressure and cholesterol levels.

“It’s a really important first step to reach,” even if it doesn’t meet patients’ expectations, said study author Dr. Kimberly Gudzune, an internist and researcher at Johns Hopkins University’s medical school.

The study was published Monday in Annals of Internal Medicine.

The research review included 39 rigorous studies involving 11 popular diet programs that include support or counseling services and involve fees for products or services. Most studies compared the programs with standard diet information or behavioral counseling patients get from health care providers; long-term results for Weight Watchers and Jenny Craig were mostly better than the comparisons.

The researchers didn’t attempt to make head-to-head comparisons of different diet plans. They note that the Affordable Care Act makes obesity screening and counseling more accessible to many Americans, and that with two-thirds of U.S. adults overweight or obese, it’s important for doctors to know which diet plans work.

Diet companies had no role in the research, Gudzune said.

Weight Watchers and Jenny Craig include behavioral counseling, coaching or social support — important for long-term weight-loss success, according to an Annals editorial.

Weight Watchers costs about $43 monthly, which includes costs for attending online or in-person support groups or coaching sessions. Participants can buy the company’s low-calorie products or buy their own food, but each item is assigned points and dieters aim not to exceed a daily point limit.

Jenny Craig provides pre-made meals and costs about $600 monthly.

Michele Rouse, an administrative coordinator at Johns Hopkins’ medical school who used to work for Gudzune, said she had lost seven pounds since starting on Weight Watchers a month earlier and had already seen a drop in her elevated blood pressure. Rouse said she didn’t know much about the new study and picked Weight Watchers because she’d had success with it years ago.

It’s too soon to tell whether the program will help her reach her 70-pound weight-loss goal, but Rouse said it’s a sensible plan that’s more like a lifestyle change than a harsh diet.

“You’re not starving yourself,” said Rouse, 49.