People are born with an inherited body type based on skeletal frame and body composition. Most people are unique combinations of the three body types: ectomorph, mesomorph, and endomorph. Ectomorphs are long and lean, with little body fat, and little muscle. They have a hard time gaining weight.A healthy body composition is one that includes a lower percentage of body fat and a higher percentage of non-fat mass, which includes muscle, bones, and organs.