Which macronutrient provides the most energy per gram?

• A. Fat (9 kcal per gram).
• B. Alcohol (7 kcal per gram).
• C. Carbohydrate (4 kcal per gram).
• D. Protein (4 kcal per gram).

Answer: (A)

Energy density is the amount of energy a food provides per gram of nutrient. Among the macronutrients, fat yields the most energy per gram—about 9 kcal/g. Carbohydrate and protein each provide about 4 kcal/g, which is why they are less energy-dense than fat. Alcohol can deliver about 7 kcal/g, but it’s not classified as a macronutrient that supports body functions in the same way as fat, carbs, and protein. Because fat supplies the highest energy per gram, it is the most energy-dense macronutrient.