Study Shows No One Knows Which Diets Work Best

No one really knows which diets work and which are a waste of time, with the possible exception of Weight Watchers, U.S. researchers reported on Monday.

A review of 10 separate studies of weight-loss programs showed there was very little hard data to support any commercial or nonprofit diet approach, the researchers found.Only Weight Watchers had scientific research to back up its simple approach of keeping a food diary and focusing on low-calorie foods, especially vegetables and whole grains, they wrote in the Annals of Internal Medicine.”With the exception of one trial of Weight Watchers, the evidence to support the use of the major commercial and self-help weight-loss programs is suboptimal,” Dr. Adam Tsal and Thomas Wadden of the University of Pennsylvania wrote.The pair started out scanning more than 1,500 diet studies, but rejected most because they were done outside the United States, had fewer than 10 participants, lasted only a few weeks or differed from the diet as offered to the public.They also looked for at least one year of follow-up and did not include commercial self-help programs based on books alone or meal replacement plans.They ended up with 10 studies that included Weight Watchers, Jenny Craig, eDiets.com and the nonprofit Overeaters Anonymous group.”Currently, the three largest nonmedical commercial programs in the United States are Weight Watchers, Jenny Craig and LA Weight Loss,” Tsal and Wadden wrote.The largest trial showed dieters using the Weight Watchers program lost and kept off 3.2 percent of their weight after two years.”Weight Watchers, at $12 per week, is moderately priced, whereas the weekly costs of Jenny Craig’s prepackaged meals ($70 to $100) make it expensive,” they noted.”Controlled trials are needed to determine the amount of weight lost and health benefits associated with Jenny Craig and LA Weight Loss programs,” the study said.Some diets can be dangerous, according to the researchers.”Medifast offers both very-low-calorie and low-calorie meal replacement plans, which participants may purchase directly from the manufacturer,” they wrote. But it does not require medical supervision, as is advised by government experts for very-low-calorie diets.”Serious complications, including death, have been reported in obese persons who consumed very-low-calorie diets without medical supervision,” they wrote.Many Internet-based programs are available, but there is little study to show whether they work, the researchers said. (Source: Reuters Health, January 2005)