If you’ve ever started a workout regimen and found yourself down an internet rabbit hole of fitness tips, you’re likely aware of the three body types, or “somatotypes.” Common advice dictates that the best way to achieve your fitness goals is to customize your exercise and nutrition plan to your unique somatotype. But is this true? Here’s what the science says.
Like many ideas about human “types” (shout-out to the Myers-Briggs test), somatotypes got their start in the 1940s. They were conceived by a psychologist and doctor named William Herbert Sheldon who believed that a person’s psychology had roots in biology. In a 1940 publication entitled “The varieties of human physique,” he analyzed 4,000 nude photos of male college students. (Where did he get 4,000 nude photos of college students? It turns out that incoming freshmen to Ivy League schools had to pose for these “posture photos,” as the images were believed to divine something about their health and intellect.) From this data, Sheldon classified the human form into three types:
But that wasn’t all. Sheldon went on to make predictions about psychology from these physiological descriptions; endomorphs were supposed to be relaxed and extroverted, mesomorphs were more assertive and aggressive, and ectomorphs were more introverted and thoughtful. He even used these associations to say that teenage delinquency was a result of a mesomorphic body type (and, alarmingly, that “selective reproduction” was its solution). Sheldon’s concept of “constitutional psychology,” as it was called, has since been discredited.
Sure, linking the way someone looks to the way they think is pretty far-fetched. But linking the way they look to the way they should exercise — doesn’t that make more sense? It doesn’t really, and here’s why.
Beyond their unsavory origins and lack of scientific validation, the glaring problem with somatotypes is that they’re just a description of a person’s body at one point in time, and, well, bodies change. An ectomorph can start lifting weights and become a mesomorph; an endomorph can kick their diet and exercise regimen into high gear and become an ectomorph. Studies bear this out: When researchers put untrained men on a weightlifting program, the people who started with the least muscle at the beginning had the biggest gains at the end of 12 weeks. Even though you might call these individuals ectomorphs and conclude they shouldn’t have much capacity for building muscle, build muscle is exactly what they did. Likewise, a recent study showed that even identical twins end up with different bodies (and even different muscle fibers) after enough training.
There’s little evidence to support the idea that having one type of body means you should follow one type of training program. In fact, many of these body-type recommendations smack of the Barnum effect: lots of seemingly specific advice that could, in reality, apply to anybody. For example, this article recommends doing weight-lifting exercises with compound movements for all three body types, and this one tells every body type to strive for high repetitions. Good fitness advice is good fitness advice, regardless of your so-called somatotype.
That’s not to say workouts shouldn’t be tailored to the individual. If you have a lot of fat to lose, cutting your calories and doing high-intensity interval training is better than the high-calorie, low-cardio program that’s ideal for someone who wants to get bigger. But your body type is not your destiny. You’ll gain and lose fat and muscle at different rates depending on your training, diet, and countless other factors, and you can become a different body type with enough work. When it comes to the right training plan for you, it’s less about what you were born with and more about what you want to become.
Check out my related post: Why should you exercise?