Body composition is the proportion of fat and fat free mass in your body. A healthy body composition is one that includes a lower percentage of body fat and a higher percentage of fat free mass, which includes muscles, bones and organs. Body composition is measured to assess your health and fitness level. Your body fat percentage is essential to know when evaluating your health. Measuring weight alone is not a complete accurate assessment of health or fitness.Everyone needs some body fat but too much fat result in obesity.