The slow carbs diet, on the other hand, allows you to eat carbs as long as they have a low glycemic index. But what does that mean? As Fitness Magazine tells it, “the glycemic index (GI) is a system of ranking carbohydrates based on how much they raise blood-glucose levels.” When you eat bad carbs (think sugar, cookies, donuts etc.) your blood-sugar level rises, your body releases more insulin to regulate those levels and then when your blood-sugar level crashes, you’re irritable, crabby, hungry, and craving more bad carbs. It’s a vicious cycle.