Three years ago, I took it upon myself to radically change my diet—and, in turn, to see if I could make any muscular gains. A relative of mine told me that no matter what I did, it would probably be hard for me to do because I am, in his words, a “hard gainer.” In other words, I’m an ectomorph: lanky and lean, with a high metabolism, little body fat, and not a lot of muscle.
Ectomorph is a common term at the gym, along with mesomorph and endomorph. Taken together, they represent three generalized body types, or somatotypes. Ectomorphs are long and lean. Endomorphs are rounded, with lots of muscle and body fat, a stockier structure, and a slower metabolism. (Think of football linemen.) Mesomorphs are athletic and muscular, capable of gaining weight or losing weight easily thanks to their efficient metabolisms.
Body types are often discussed among bodybuilders, nutritionists, and personal trainers. How someone is built typically informs what someone should eat and the exercises someone might do in order to achieve a particular physical end. But the history of somatotypes, and their legacy (and usefulness) today, is not so straightforward as it might appear.
Sheldon’s Theory
The somatotypes are the product of William Sheldon. In the 1940s, the American psychologist and physician posited that the psychologies of people were biologically predetermined by their physiological makeups. What you looked like, Sheldon argued, correlated with how you behaved. Long and lean ectormorphs were thought to be sensitive, introverted, and shy. Muscular mesomorphs were thought to be active, assertive, and aggressive. Rounded endomorphs were expected to be extroverted and relaxed, but also lazy.
Sheldon’s research was highly irregular and controversial. He based his assumptions, for instance, off of nude pictures of college students, who thought they were being photographed for the purpose of posture correction. (Which would have been weird enough.) He assigned personality traits to each person’s shape—and, from there, linked someone’s shape to their behavior. “Through body type,” wrote Amanda Mull in The Atlantic, “Sheldon believed it could be possible to predict things like future criminal behavior and a child’s potential for leadership—quite literally, that physique was destiny.”
Sheldon’s ideas came on the heels of the eugenics movement of the early 20th century, now universally seen as a repugnant and racist. And constitutional psychology, that field of research that grew out of Sheldon’s notions, was widely debunked over time.
The Problems of Body Typecasting
Drawing straight lines from someone’s physical shape to their personalities is obviously fraught. (As Mull points out, fat people are commonly stereotyped with traits of “laziness, carelessness, and low intelligence.”) Research conducted by the University of Texas at Dallas demonstrated just how hard it can be to shake people free of their biases when it comes to drawing conclusions about others based on what they look like.
In a study using 140 gray 3D models, with the same face and standing with the same posture, participants were asked to assign personality traits—picked from a list of 30 adjectives they were provided—to the models based on their body shapes. Male models with broad shoulders were considered extraverted but irritable. Rectangular female models were described as shy. What the study showed was that positive or negative impressions of other people are based sometimes entirely on their body shape. Thinner models were thought of as curious, while fatter models were described as careless.