While each of these macronutrients provides calories, the amount of calories that each one provides varies.
Carbohydrate provides 4 calories per gram.
Protein provides 4 calories per gram.
Fat provides 9 calories per gram.
This means that if you looked at the Nutrition Facts label of a product and it said 12 grams of carbohydrate, 0 grams of fat, and 0 grams of protein per serving, you would know that this food has about 48 calories per serving (12 grams carbohydrate multiplied by 4 calories for each gram of carbohydrate = 48 calories).
Besides carbohydrate, protein, and fat the only other substance that provides calories is alcohol. Alcohol provides 7 calories per gram. Alcohol, however, is not a macronutrient because we do not need it for survival.
A NOTE ON MICRONUTRIENTS
Although macronutrients are very important they are not the only things that we need for survival. Our bodies also need water (6-8 glasses a day) and micronutrients. Micronutrients are nutrients that our bodies need in smaller amounts, and include vitamins and minerals. (See the Vitamins and Minerals handout for more information).