Starch in food plays an important role in the metabolic process. Starch is a carbohydrate that aids in the conversion of glucose to energy. Many vegetables are high in starch, including corn, potatoes and squash. Starch can also be added to the diet by consuming whole wheat bread.
As of 2014, CDC guidelines indicate that 45 to 65 percent of calories in a diet should come from carbohydrates. Sixty percent of total carbohydrate calories should come from a starchy carbohydrate. Carbohydrates contain 4 calories per gram. Protein also has 4 calories per gram. In comparison, fat contains 9 calories per gram, and alcohol has 7 per gram.