In a perfect world, we could go to the gym for 30 minutes and gain massive amounts of muscle while burning away all the fat. Unfortunately, this does not happen. Similar to other areas of the body, there is a balance between muscle breakdown and muscle formation. The stress applied to us by the outside world dictates which direction these mechanics will sway. This is the fundamental concept of adaptation. For example, if an animal comes across a large meal, it will store this meal as fat as well as create muscle to allow it to hunt for another meal. If, however, it does not eat at all, the muscle may begin to atrophy and will be used as fuel reserves along with the fats.