Solid evidence that major commercial weight loss programs are helpful over the long term is hard to come by, a study has found. What evidence there is indicates that while many people lose weight, many also drop out, or regain at least half of the weight they lost within two years.

The study examined data collected on a variety of programs, including those like Weight Watchers where people lose weight at a gradual rate without medical supervision, and more drastic, very low-calorie techniques such as OPTIFAST where dieters need to be followed by health professionals.

“There wasn’t really, for the most part, that much evidence to support” these programs, study author Dr. Adam Gilden Tsai told AMN Health.

However, every dieter is different, and many will likely shed pounds for good on some of these programs, Tsai noted. But before choosing one, dieters should be “savvy,” he said, and decide whether it’s worth what’s involved and the cost.

Co-author Dr. Thomas A. Wadden recommended that dieters first try to drop the weight on their own, then ask their doctors about which commercial program would be best only if the self-imposed weight plan doesn’t work.

Generally, the “three pillars of weight loss” are smaller portions, eliminating hidden calories or fat, and being active on a regular basis, Tsai noted.

To evaluate commercial weight loss programs, the researchers - both based at the University of Pennsylvania in Philadelphia - searched weight loss company web sites for the cost of the program, and called company representatives if the information was not provided.

To determine how well the programs work, the researchers reviewed all available research into the programs’ merits, finding studies about eDiets.com, Health Management Resources, Take Off Pounds Sensibly, OPTIFAST, and Weight Watchers.

Reporting in the Annals of Internal Medicine, the researchers found two studies where Weight Watchers dieters who regularly attended the program lost approximately 5 percent of their body weight in 3 to 6 months. This is enough of a weight loss to improve certain health problems, Tsai noted, including cholesterol, blood pressure and diabetes.

Among very low-calorie, medically supervised dieters, studies showed that people who finished the programs lost up to 25 percent of their initial weight, but were at high risk of regaining at least half of it back soon after, or dropping out of the program entirely.

Furthermore, medically supervised programs can cost around $2,000 for three months, while Weight Watchers typically charges only $12 per week. “You may not lose a lot of weight on Weight Watchers, but you won’t lose a lot of money, either,” Wadden said.

In terms of internet-based diets such as eDiets.com, there was little evidence to show whether they work or not, although research suggested that people fared better if they got regular e-mails from a counselor.

Wadden added that people tend to regain the weight they lost following a program because once it’s finished, they return to their normal eating habits. Furthermore, the body is always trying to fend off “what it perceives to be starvation,” he noted, and losing weight triggers hormone changes that make it difficult to keep shedding pounds.

SOURCE: Annals of Internal Medicine, January 1, 2005.