Two 100 g snacks each contain 500 kcal. Snack A is high-fat with most energy from fat; Snack B gets most energy from carbohydrates. From the standpoint of energy density per gram of macronutrient, which snack requires less mass of macronutrient to provide the 500 kcal and why?

• A. Snack A (high in fat) requires less mass of macronutrient because fat provides 9 kcal/g, more than twice the energy per gram of carbohydrates or protein at 4 kcal/g.
• B. Snack B requires less mass because carbohydrates have lower water content in most snacks, making the carbohydrate portion denser and more calorically concentrated by product mass.
• C. Snack B (high in carbohydrate) requires less mass because carbohydrate molecules are metabolically more efficient and therefore release more usable energy per gram when digested.
• D. Both require equal macronutrient mass because total calories are identical and the body converts all macronutrients to a standard energetic currency with equal mass requirements.

Answer: (A)