So you think you know how to eat right—what foods are healthy, what foods keep the weight off—yet you can't avoid peeking at the latest fad diet. A voice inside says you'd lose the weight without cutting calories if you ate your cheeseburger without the bun, drank a liquid protein concoction, and stopped eating for three hours before you go to bed, or ate exactly 40 percent of calories from carbohydrates, 30 percent from protein, and 30 percent from fat at each meal and snack.Sound crazy? Sure it does. Yet at any given time, about two-thirds of us are trying to lose weight or keep it off. That helps make weight loss a $43-billion-a-year industry.