Multi-step integrative calculation and reasoning: A person maintains weight at 1,800 kcal/day. They add a 700 kcal/day surplus for 8 weeks and start resistance training; measured changes: +1.5 kg lean mass (via DEXA) after 8 weeks. Using 7,700 kcal/kg as the energy equivalent of gained tissue, estimate the fat mass gained (kg). Show all steps and justify whether the observed change in body composition is consistent with the energy surplus.

• A. Approximately 3.6 kg of fat gained (plus 1.5 kg lean), which is consistent with the 700 kcal/day surplus over 8 weeks when using 7,700 kcal/kg.
• B. Fat gain cannot be estimated from caloric surplus or measured lean mass; therefore any numeric estimate is invalid and should be discarded.
• C. No fat gain; all surplus calories would be converted to muscle when resistance training is performed, so fat gained is 0 kg regardless of caloric surplus.
• D. About 10 kg of fat gained because the body stores calories at an efficiency that always triples the theoretical weight gain.

Answer: (A)