Lipids provide how many kilocalories per gram?

• A. 9 kcal/g
• B. 4 kcal/g
• C. 7 kcal/g
• D. 12 kcal/g

Answer: (A)

Energy density of macronutrients is being tested here. Lipids yield more energy per gram than carbohydrates or proteins because their fatty acid chains are highly reduced and carry many C–H bonds; when oxidized in metabolism, those bonds release a lot of energy. That’s why fats provide about 9 kilocalories per gram, while carbohydrates and proteins each provide about 4 kcal per gram. (Alcohol provides roughly 7 kcal per gram, but it isn’t a stored nutrient like fats.) So the best answer is 9 kcal per gram.