There is little evidence to support the use of many commercial weight loss programs, according to a study in the US, which suggests that the search for new, more effective methods will continue to preoccupy dieters.
The study, published in the 1 January issue of the Annals of Internal Medicine, examined the evidence for the major commercial and organized self-help weight loss programs in the United States that provide in-person or online counseling.
It only included programs supported by randomized trials of at least 12 weeks long that included a follow-up evaluation lasting at least one year. These were eDiets.com, Health Management Resources, Take Off Pounds Sensibly, OPTIFAST, and Weight Watchers.
"Of three randomized, controlled trials of Weight Watchers, the largest reported a loss of 3.2 per cent of initial weight at two years," write authors Adam Gilden Tsai and Thomas A. Wadden from the University of Pennsylvania.
Research on very-low-calorie diet programs showed patients who completed treatment lost approximately 15-25 per cent of initial weight but these were associated with high costs, high attrition rates, and a high probability of regaining 50 per cent or more of lost weight in one to two years.
Commercial interventions available over the Internet and organized self-help programs produced minimal weight loss, added the authors.
"Because many studies did not control for high attrition rates, the reported results are probably a best-case scenario."
"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. Controlled trials are needed to assess the efficacy and cost-effectiveness of these interventions," they concluded.
More than 1 billion adults are overweight in the world, with at least 300 million of them clinically obese.