The word "endomorph" is a once-common term for a human body type characterized by a greater percentage of fat and sturdiness of bone. The endomorphic body typically has excess fat stored in the trunk and thighs, with extreme specimens having rounded, sometimes bulbous shapes. The endomorph is one of the three somatotypes, classifications of human bodies based on the distribution of muscle, bone, fat and other tissues.
The other two somatotypes are ectomorphs and mesomorphs. Ectomorphs tend to have long bones and a predisposition toward thinness. Mesomorphs, in contrast, are heavily muscled but also have little body fat. Scientists once believed a person’s body type remained largely the same even if he or she acquired characteristics of another. For example, an athletic mesomorph could gradually begin to look more like an endomorph with age and lack of exercise.
The terms endomorph, mesomorph and ectomorph were created by American psychologist Dr. William Herbert Sheldon. Sheldon based the somatotypes on the three cell types formed during embryonic development. Endodermal cells form the digestive tract, mesodermal cells grow into muscle tissue and the circulatory system, and ectodermal cells become the nervous system and skin. Sheldon theorized that endomorphs had longer digestive systems that contributed to their body mass and tendency to gain weight. The three body classification terms are still used as guidelines by exercise specialists, but much of Sheldon’s work in this area has long been discredited.
Sheldon’s use of somatotypes became particularly problematic when he tried to link specific personality traits to body types. Endomorphs were believed to be easygoing, tolerant extroverts who sought pleasure, especially with food. Mesomorphs, Sheldon theorized, were more active and aggressive, and ectomorphs were typically sensitive, intelligent introverts with a tendency toward nervous excitement. Many modern scientists find that Sheldon’s work overlaps uncomfortably with eugenics, the selective breeding of human beings. Eugenics gained notoriety in the 1930s and 1940s when the Nazis forcibly sterilized hundreds of thousands of German citizens who had disabilities and other traits deemed undesirable.
The term "endomorph" is more casually used these days to help people identify their own metabolic tendencies. Exercise magazines and fitness trainers encourage specific regimens for overweight people, emphasizing different exercises to help them shed unwanted pounds. Such regimens tend to emphasize fat-burning aerobic activities such as running, walking, cycling and any movement that elevates the heart rate. Even those who still use these terms note that the classifications are not rigid, and that many human bodies tend to be combinations of the somatotypes.