Macronutrients

Macronutrients are nutrients that the body uses in great amounts. Some examples are proteins, carbohydrates and fats. Macronutrients provide a good amount of calories to the body (which gives it energy) and it also helps perform other functions. The main purpose is to provide energy, but the amount of energy that each macronutrient provides varies. As we know, Carbohydrates and protein provide 4 calories per gram and fats provide 9 calories per gram. Lastly, macronutrients contribute to the taste, consistency and appearance of foods to make a more varied and enjoyable diet. (Davey)

http://lowcarbdiets.about.com/od/glossary/g/glosstermmacro.htm
http://www.diet.com/g/macronutrients