Macronutrients are nutrients that provide calories. Calories are used as energy in your body. Nutrients are substances needed for growing, digestion, and other body functions. Since "macro" means large, macronutrients are nutrients needed in large amounts. There are three categories of macronutrients:
Carbohydrates are mostly in foods in the starchy foods groups, but also in vegetables, fruits, dairy foods, and sugars. The primary sources of protein are meats and dairy products. Fat can be found in dairy and meats. Fat can also be added to food, such as salad dressing or margarine. Fat can also be added when food is made, such as chips, cookies, or pizza.
When food is digested, the protein is broken down into amino acids; the fat is broken down into fatty acids; and the carbohydrate is broken down into glucose. It is easy to see, then, that most of the glucose (sugar) in your blood comes from the carbohydrate in foods.