11 low-carb myths that will make you fat: almost one in three Americans is cutting down on carbs, believing it's carbs, not calories, that pack on the pounds. But if you're buying into this hype, you might need to buy yourself some bigger clothes. Here's what you really need to know.(health check)

Test Your Carb IQ

(1) You can lose weight on a low-carbohydrate diet even if you take in more calories than you normally would. True or False?

False. When you look closely at studies in which people lost weight on low-carb diets, they generally are fewer calories. In one much-publicized study, people Oil a low-carb, all-they-could-eat diet lost more weight than other dieters--but also averaged 190 fewer calories a day. "Nothing curbs the appetite like monotony," says David Katz, M.D., Yale University School of Public Health professor and author of The Way to Eat.

(2) Reducing the carbs in a food also reduces its calories. True or False?

False. Manufacturers often replace carbs with protein, which doesn't cut calories, since both nutrients contain 4 calories per gram. If carbs are replaced with nuts, for example, you often get more fat--and more calories (fat has 9 calories per gram). That said, some low-carb products are lower in calories and fat--but you need to read individual labels to find out.

(3) You'll feel more full after eating 100 calories of fat than after eating 100 calories of carbs. True or False?

False. "Fat is the least filling nutrient," says Dr. Katz. "Research shows that protein satisfies best and longest, followed by foods high in complex carbohydrates, such as beans and whole-grain cereals." One reason fat is less satisfying is that it's the most calorie-dense nutrient: 100…