Proof of diet plans' effectiveness slim

PHILADELPHIA -- A review of 10 of the nation's most popular weight-loss programs found there was not enough evidence to support the claims many of them make about helping people shed pounds and keep them off.

Of the programs that researchers examined, only Weight Watchers had strong documentation that it worked -- with one study showing that participants lost around 5 percent (about 10 pounds) of their initial weight in six months and kept off about half of it two years later.

However, the researchers who conducted the review published in today's Annals of Internal Medicine stressed that the lack of scientific evidence should not be viewed as an attack on diet programs.

"There are no data on weight loss when you go to a health club, either," said Thomas Wadden, a University of Pennsylvania weight-loss expert and the study's co-author. "We hope that doctors and patients will use this information to make more informed decisions."

The weight-loss plans examined included Jenny Craig Inc., which typically provides prepared meals and diet and exercise counseling.

Lisa Talamini, chief nutritionist for the Carlsbad, Calif.-based company, said Jenny Craig will soon start a large study of the sort urged by the review authors.

She also cited a recent analysis by The Cooper Institute, a research organization that focuses on exercise, that found people who followed Jenny Craig for a year lost 15 percent, or an average of 22 pounds, of their initial body weight.

The authors of the latest review could not find any published evaluations about another big commercial plan, LA Weight Loss. And they said there was insufficient evidence to prove the effectiveness of self-help programs like Overeaters Anonymous and Take Off Pounds Sensibly.

As for doctor-supervised, low-calorie diets Optifast and Health Management Resources, which cost around $2,000 for the first three months, the data on their long-term success rates are not highly promising, researchers said.

However, they said such plans still can be appropriate for severely overweight people who need aggressive weight loss.

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