Which macronutrient provides the most energy per gram?

Which macronutrient provides the most energy per gram?

• A. Carbohydrates provide about 4 kcal/g
• B. Alcohol provides about 7 kcal/g
• C. Fats (lipids) provide about 9 kcal/g
• D. Proteins provide about 4 kcal/g

Answer: (C)

The energy density of macronutrients shows that fats provide the most energy per gram. Fats yield about 9 kilocalories per gram, because their molecules are rich in carbon–hydrogen bonds that release a lot of energy when oxidized in the body. In contrast, carbohydrates and proteins each yield about 4 kilocalories per gram, since their structures are more oxidized and contain more oxygen, yielding less energy per gram. Alcohol provides roughly 7 kilocalories per gram, but it isn’t a macronutrient; it’s an energy source, not one of the body’s essential macronutrients. So, fats have the highest energy per gram among macronutrients.

The energy density of macronutrients shows that fats provide the most energy per gram. Fats yield about 9 kilocalories per gram, because their molecules are rich in carbon–hydrogen bonds that release a lot of energy when oxidized in the body. In contrast, carbohydrates and proteins each yield about 4 kilocalories per gram, since their structures are more oxidized and contain more oxygen, yielding less energy per gram. Alcohol provides roughly 7 kilocalories per gram, but it isn’t a macronutrient; it’s an energy source, not one of the body’s essential macronutrients. So, fats have the highest energy per gram among macronutrients.