Macronutrients are nutrients that supply energy or calories needed for growth, metabolism and other functions of the body. Carbohydrates, proteins and fats are types of macronutrients.
Carbs are the primary source of fuel for the human body. They are simple or complex sugar molecule structures. Complex carbs contain two or more sugar molecules. Milk and fruit contain simple carbs, while starch, fiber and glycogen are examples of complex carbs.
Proteins transport nutrients throughout the body and maintain fluid and acid-base balance. Some proteins even work as antibodies. Fats are used as an energy reserve. Fats provide essential fatty acids and carry fat-soluble nutrients, such as vitamins, alpha-carotene and lycopene, throughout the body.