Macro partitioning

Muscle hypertrophy is driven by recurrent periods of positive net protein balance (NPB) resulting from resistance exercise coupled with protein feeding, rather than solely by transient increases in muscle protein synthesis (MPS) rates in the fasted state.

Do not train fasted if your goal is maximum muscle growth. Resistance exercise stimulates both muscle protein synthesis and breakdown, but in a fasted state, breakdown wins, resulting in a net loss. To build muscle, you must consume protein close to your workout to ensure your body stays in a positive protein balance over time.