An individual consumes an extra 300 kcal/day from fat compared to their usual energy needs. Evaluate the approximate monthly weight gain attributable to that surplus, assuming 1 lb body fat ≈ 3500 kcal. Show your reasoning.

• A. Exactly 1 pound per month because the body always converts 3,000 kcal into 1 lb of fat regardless of macronutrient source.
• B. Approximately 0.86 pounds in a month because fat is stored inefficiently and most excess dietary fat is excreted.
• C. No weight gain will occur because adipose tissue cannot expand after early adulthood and excess calories are directed to muscle hypertrophy only.
• D. Approximately 2.57 pounds gained in a month (9,000 kcal surplus ÷ 3,500 kcal/lb ≈ 2.57 lb); this is the best estimate.

Answer: (D)