Of the various commercial diet plans, Weight Watchers is most successful in helping overweight and obese individuals shed pounds and stick to healthy ways, according to a new study published in the June edition of Consumer Reports.

Slim-Fast and two stages of the Atkins diet produced the most weight loss after six months, and Slim Fast and the vegetarian Ornish diet produced the best weight loss after a year.

But Weight Watchers came in tops when combined with other factors such as nutritional value and dropout rates, according to Consumer Reports' Senior Editor Nancy Metcalf.

"It was the only one rated good for long-term adherence, which is one of the reasons it was rated quite good overall," she said. "It's also extremely nutritionally balanced. It's the one that doesn't exclude any food groups."

Diets had to have been studied among at least 30 people trying the program, and the results had to be published in peer-reviewed scientific journals in order to qualify for the Consumer Reports rating. Thus, eDiets, Jenny Craig, Volumetrics and two versions of the South Beach diet weren't included due to inadequate or nonexistent data.

Slim Fast, a meal-replacement plan in which participants substitute most of breakfast and lunch with a Slim Fast bar, shake or smoothie, then eat a regular dinner, came in second overall in the Consumer Reports study.

"It's another technique that's tried and true in the weight-loss field, which is controlling people's portions," Metcalf said.

But the bottom line is overweight and obese individuals only lose weight when they burn more calories than they consume, according to nutrition experts. The diets in the study, as a result, mostly ranged from 1,500 to 1,600 calories per day.

Other sources: Consumer Reports