Caloric surplus required for lean muscle gain.
Muscle growth requires a slight caloric surplus — eating more than your TDEE. The size of the surplus determines how quickly you gain weight, but not how quickly you gain muscle. A smaller surplus (150–300 kcal) minimizes fat gain while still supporting muscle growth.
Beginners can build muscle faster and can afford a larger surplus. Advanced athletes gain muscle more slowly and need tighter control of their surplus to minimize fat accumulation.