Support for this idea comes from more than a dozen randomized trials that have compared various types of diets. Though some show that low-carb diets result in greater weight loss during the first six months, any advantages disappear after one year.
In a longer-term study published in the New England Journal of Medicine, 800 overweight adults were randomly assigned to one of four diets, each with a different percentage of carbs, fat, and protein. Calories were also restricted. After two years, all four groups had lost the same amount of weight--about nine pounds on average.
Likewise, in a two-year randomized study that pitted a low-carb diet against a low-fat diet, the low-carb eaters lost no more weight. However, they did have a greater increase in their HDL (good) cholesterol levels. On the other hand, they were more likely to experience side effects such as bad breath, hair loss, constipation, and dry mouth.
The bottom line: Carbohydrates aren't the main cause of weight gain, and you don't have to shun them to shed pounds.