An article just came out (see the link) about a study that was published in the Journal of the American Medical Association. The study was done with participants in a weight loss study over a 12 week period. Three groups: the low-fat group, low-glycemic index group and the low-carbohydrate group.
You can read the study for yourself, but basically your body metabolism burns faster on certain diets. The slowest metabolism was the low-fat group. However, the next group was the low-glycemic group, which does still involve still eating whole grains. That group burned about an extra 200 calories a day over the low-fat group. However, the winner–the low-carb group, burned 300 more calories a day over the low-fat group, merely because of the type of foods consumed and less whole grains and starchy vegetables.
So, if you are trying to lose weight and not following a low-carb diet, you are throwing away the opportunity to burn an extra free 300 calories a day with no physical labor involved. 300 calories is equivalent to a vigorous one hour exercise class.