Metabolism is a complex process that determines how many calories your body burns. It's not as simple as just looking at your lean body mass and calculating a specific number. Your metabolism can vary even among people with similar characteristics. The best explanation I've heard is that your body has a range of calories it will burn with the same lean body mass. Your metabolism can become more or less efficient based on various factors like your environment, stress levels, sleep quality, and exercise type. These factors can influence your body's decision to store or burn calories. Think of it like an AI car that can decide to burn more or less gas with the same engine size.