The body utilizes fats as a source of energy during exercise through a process called lipolysis, where stored fat is broken down into fatty acids and glycerol. During prolonged or moderate-intensity activities, the body relies on fat as a primary energy source, particularly when glycogen stores become depleted. This transition maximizes endurance by holding onto limited carbohydrate reserves for high-intensity efforts. As exercise duration increases, the efficiency of fat oxidation improves, allowing the body to sustain performance. Proper training and nutrition can enhance this energy utilization, optimizing overall exercise effectiveness.