South Beach in a Nutshell

WHAT IT IS

A three-phase plan that has been likened to the low-carbohydrate Atkins program because during the first two weeks, South Beach eliminates most carbs, including bread, pasta, potatoes, fruit and most dairy products. In Phase 2, healthy carbs, including most fruits, whole grains and dairy products are gradually reintroduced, but processed carbs such as bagels, cookies, cornflakes, regular pasta and rice cakes remain on the list of foods to avoid or eat rarely. Ditto for carrots, corn, bananas, raisins, pineapple, fruit juice and watermelon. This phase lasts until the weight goal is reached. In Phase 3, adherents are urged to stick mostly with the same foods as in Phase 2. Agatston notes, however, that lapses are inevitable and dieters may need to "switch back to Phase 1 for a week or two" when they overindulge and regain weight.

PHILOSOPHY

The program is based largely on reducing or eliminating foods with a high glycemic index -- a measure of the rise in blood sugar after eating a particular food. The South Beach Diet, Agatston writes, "corrects the way your body reacts to the very foods that made you overweight," especially sugar.

Reality Check: "The glycemic index is interesting," notes Wadden, but there isn't enough evidence to prove its effectiveness in weight loss. Adds Wing, "For weight loss, the bottom line continues to be calories, not the glycemic index."

WHAT IT PROMISES

Eight- to 13- pound loss in the first two weeks; about one to two pounds per week after that. Belly fat is said to vanish first, though Agatston doesn't explain why.

HOW IT STACKS UP

Calories aren't counted, but based on serving sizes and ingredients provided in sample menus and recipes, intake in all phases runs about 1,200 to 1,400 calories daily, provided that you eat reasonable portions. This calorie level should produce weight loss of about a pound per week. Fat - much of it healthful fat from salmon and olive oil - provides 40 to 50 percent of calories, higher than the 30 percent or less targeted by low-fat diets and groups such as the American Heart Association. According to the Healthy Eating Index, South Beach Phase 1 could fall short on fruit and grains for women and men, and may have too much saturated fat, but it appears to hit the mark on milk, vegetables, meat, cholesterol and variety. Phase 2 may still skimp on grains and some dairy products and may have too much cholesterol because of eggs. But for women especially, it appears to score well on vegetables, fruit, meat, saturated fat, sodium and variety. Men may need more vegetables.

PHYSICAL ACTIVITY QUOTIENT

Newspaper ads promise that exercise is not needed for success on the South Beach Diet. The book offers just a half-page on physical activity, which Wadden says is surprising given that Agatston is a cardiologist. "It's true that you don't have to exercise to lose weight," Wadden says, "but it sure helps." And as Wadden notes, increased physical activity is good for improving such other things as energy, sleep, mood and blood pressure.