are classified according to glycemic index (GI), a measure for how rapidly the food is digested. High-GI carbohydrates are considered bad. "Bad carbohydrates", such as those in potatoes, pasta, rice, and white bread, may not be taken together with "lipids". According to Montignac's theory, these combinations will lead to the fats in the food being stored as body fat.
Montignac's theory is disputed by nutrition experts, who claim that any calorie intake that exceeds the amount that the body needs will be converted into body fat. Despite these scientific doubts, there are other serious scientific studies which endorse this method (See British Journal of Nutrition article in external links). Montignac sold 15 million books about his diet.
Official Montignac Website