Most dietitians say that's baloney.
You see, not all carbohydrates are the same. Although you can't tell by looking at the food, the molecules of some carbs are like strands of tightly strung beads, while others are shaped more like a tree with many branches. This provides a quick spurt of energy for a strenuous run but can't properly sustain your body's regular activities. Any food that measures greater than 70 is one you need to watch out for. High-GI foods can promote weight gain because the bursts of energy they provide may be followed quickly by an energy slump and hunger, leaving you reaching for another snack.