The difference between aerobic and anaerobic metabolism lies primarily in how the body produces energy. Aerobic metabolism occurs when oxygen is available, typically during sustained, moderate-intensity exercise, and relies on carbohydrates and fats as fuel. This process supports long-duration activities. In contrast, anaerobic metabolism occurs when there is insufficient oxygen, primarily during high-intensity, short-duration activities like sprinting or weightlifting, where the body relies on stored energy sources, resulting in lactic acid production. Understanding this difference is crucial for tailoring exercise programs to meet specific fitness goals.