Try this weight loss diet that's most effective

In a bid to help physicians guide obese and overweight patients who want to try a commercial weight-loss program, a team of Johns Hopkins researchers reviewed 4,200 studies for solid evidence of their effectiveness but concluded only a few dozen of the studies met the scientific gold standard of reliability.

Among the findings, the investigators found that of 32 major commercial weight-loss programs marketed nationwide, only 11 have been rigorously studied in randomized controlled trials.

And from these studies, they found only two programs are supported by gold-standard data showing that participants, on average, lost more weight after one year in these programs than people who were either dieting on their own, got printed health information, or received other forms of education and counseling sessions.

Moreover, they wrote that results in those programs were generally "modest," with participants losing on average between 3 and 5 percent more than the studies' control groups of nonprogram participants.

The researchers found Jenny Craig and Weight Watchers were backed by clinical trials that lasted 12 months or longer and showed program participants had a greater weight loss than nonparticipants.

NutriSystem also produced more weight loss at three months than counseling or education alone, but the authors were unable to find any long-term trials of that program.

Participants in the very-low-calorie meal replacement programs lost more weight than nonparticipants in trials lasting from four to six months. But the authors found only one long-term study, which showed no benefit from such a program at 12 months. The authors noted that very-low-calorie programs also carry higher risks of complications, such as gallstones.

Programs based on the Atkins diet, high in fat, low in carbohydrates, also helped people lose more weight at six months and 12 months than counseling alone. The approach "appears promising," the authors wrote.

No definite conclusions could be made about Slim-Fast and the Internet-based programs.

The study is published in the Annals of Internal Medicine.