Protein provides energy at how many kilocalories per gram?

• A. 2 kcal/g
• B. 9 kcal/g
• C. 0 kcal/g
• D. 4 kcal/g

Answer: (D)

Macronutrients deliver energy in fixed amounts per gram. Fat provides about 9 kcal per gram, while both carbohydrate and protein supply about 4 kcal per gram. Protein’s main role is to supply amino acids for tissue growth, repair, and metabolic functions, but when it is used for energy, each gram yields roughly four kilocalories. This is the value used in nutrition labeling and common estimates.