Simple and complex carbs are eventually metabolized into glucose. While simple carbs break down quickly, complex carbs take extra time. Complex carbs, such as starch, start breaking down in your mouth when saliva turns them into maltose, which is a simple carbohydrate. Maltose travels down into your small intestine where it is further broken down and absorbed through intestinal walls as glucose. Both types of carbohydrates offer 4 calories per gram, and between 45 and 65 percent of your total calories should come from carbs. If you normally stick to a 2,000-calorie diet, you need 225 to 325 grams daily. Your diet should have a balance of complex and simple carbohydrates.