Factors affecting the energy expenditure of exercises include intensity, duration, and the individual's body composition. Higher intensity workouts generally burn more calories in a shorter period, while activity duration also contributes to total calorie expenditure. Further, individuals with higher muscle mass tend to burn more energy, even at rest, compared to those with a higher fat ratio. Additionally, age and gender influence metabolic rate, altering energy expenditure during similar activities. Overall, understanding these factors can help tailor fitness programs for optimal results.