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What is an Ectomorph?

By Sheri Cyprus
Updated Mar 03, 2024
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An ectomorph is a lean body type identified by the American psychologist, William Sheldon, in his book, The Atlas of Men, first published in 1954. According to Sheldon, ectomorphs aren't just thin, but have a certain fragility to them. The ectomorph is said to have small shoulders and some muscle, but not enough musculature to have much definition in the body's shape. Ectomorphs tend to have long limbs and a straight, narrow body.

The ectomorph usually has little definition between his or her waist and hip areas. Although it's possible for ectomorphs to gain muscle through exercise, it may take longer than it would for a naturally muscular body type. Ectomorphs usually have a fast metabolism, which means that they process food energy quickly before it turns into excess fat. A problem with this characteristic can be that very thin ectomorphs who need to gain some weight in order to be healthier and less fragile may find it difficult to do so.

The other two body types in Sheldon's theory are the mesomorph and the endomorph. Endomorphs are the opposite of ectomorphs; they have naturally fuller bodies and tend to have short limbs. Endomorphs gain weight easily and have a more difficult time losing excess pounds than the other two body types. Mesomorphs gain muscle much easier than endomorphs or ectomorphs. While the mesomorph usually has a high fat-burning metabolism, he or she will gain weight easier than the ectomorph.

Ectomorphs must be sure to get enough calories each day to avoid becoming too thin and frail. In addition to having longer limbs than the other two body types, ectomorphs are said to have lighter bones and a fragile skeletal system. An ectomorph is usually tall and has a flatter chest than the endomorph and mesomorph.

Even if ectomorphs aren't tall, they tend to look that way due to their lean appearance. Stooped, as well as narrow, shoulders are attributes of the ectomorph body type. They usually have the narrowest hips of all of the body types.

Sheldon's body type theory includes personality characteristics. He views the ectomorph as the type most likely to be nervous, artistic, sensitive, and introverted. Mesomorphs are depicted as adventurous and risk-taking in Sheldon's theory, while endomorphs are said to be sociable as well as relaxed. There are many people who disagree with Sheldon's personality attributes for each body type, although they may agree with his physical analysis of his endomorph, ectomorph, and mesomorph types.

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Discussion Comments

By anon961912 — On Jul 21, 2014

Well, each bone frame has its threshold on whats over and underweight. The ecto can go 1 or even 2 points below BMI's 18.5 and still be healthy, while large frame guys can be healthy by going 2 points over like Tyson. The

BMI is flawed since it doesn't take frame into account, hence why other nations adjusted to the stereotypical build of its citizens. Like Samoa has raised its BMI threshold since they are large boned people, while in japan, they lowered it since they are small boned people for the most part (Yushin Okami and Kawajiri are exceptions).

Look up bone frame and scale yourself.

For men, if your wrists are between 6.5-7.5 inches, you are medium. Anything over or under makes you large or small frame. I don't know about the female bone frame, though.

By starrynight — On Jun 27, 2011

I personally don't think these three body types encompass everyone. Body type and composition is so diverse- I really don't think this theory does that diversity any justice.

That being said, I certainly can't bring myself to feel sorry for these frail ectomorphs! If I had a choice I would definitely choose to be a little underweight rather than overweight.

By Azuza — On Jun 26, 2011

I really don't think personality type has anything to do with body type. My mother is definitely ectomorphic and she is neither nervous or introverted. In fact just the opposite! My mom is a total people person and loves to talk to everyone.

She does have the other problems mentioned for ectomorphs, specifically she has a hard time gaining weight. She is usually a little bit underweight and can lose weight at the drop of a hat. She was sick for a few days last week and lost five pounds!

I suppose having this body type is kind of a mixed blessing. On the one hand my mom really enjoys the fact that she weighs exactly what she did in high school. On the other hand being underweight can be unhealthy.

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