Illustration showing a skinny ectomorph flexing his lanky arms.

What’s an Ectomorph Body Type? Is it Even Real?

Is “ectomorph” a real body type? Is it an accurate way to describe a naturally skinny person with a tall, narrow build? It’s a controversial word, and over the past ten years, we’ve gotten our share of flack for using it. I understand why. The body types have a dark past.

Is it a useful term? We’re naturally skinny guys with a decade of experience helping thousands of other skinny guys build muscle. Many of us describe ourselves as ectomorphs. It’s a convenient way to refer to our narrower frames and thinner bones. Should we stop describing ourselves that way?

Let’s delve into ectomorph etymology to see if there’s anything worth salvaging here.

An illustration of the ectomorph body type, showing a skinny man flexing his muscles. Illustrated by Shane Duquette.

Skinny Terminology

There are a few terms describing the skinny condition. Each is related, but they all mean something slightly different, describing our many different facets.

  • Skinny: someone with less muscle and fat than average. We often build muscle quite fast. We can often bulk quite aggressively.
  • Skinny-fat: someone with less muscle than average but too much body fat. For example, someone with upper arms smaller than 13 inches and a body-fat percentage over 20%. It’s another way of calling someone “out of shape.” They often benefit from doing a lean bulk.
  • Ectomorph: someone with a narrow frame and thin bones. It’s a term referring to bone structure. Ectomorphs can be thin, skinny-fat, overweight, or muscular.
  • Hardgainer: someone who struggles to eat enough calories to gain weight. This is the skinny guy who tries to bulk up but can’t budge the scale.
  • Non-responder: in the past, researchers used this term to describe people who failed to gain weight during muscle-building studies. Further research showed that other factors tended to explain their lack of muscle growth. The current consensus is to use the term “low-responder” instead.
  • Low-responder: someone who has a lower-than-average response to the stimulus of lifting weights. It refers to someone with bad muscle-building genetics. There’s very little overlap between non-responders and skinny guys. Most skinny guys can build muscle quite fast.

You could argue that “ectomorph” is a useful term because it describes something the other terms don’t. For example, I’ve gained 70 pounds, going from 130 to 200 pounds. I’m not skinny anymore. But I still have the same bone structure. My frame is still narrow. My bones are still thin. I’m still an ectomorph.

The Origin of the Body Types

The term “ectomorph” was coined by William Herbert Sheldon in the 1940s. It was part of his somatotype taxonomy, used to divide men into three body types: mesomorphs, endomorphs, and ectomorphs.

  • Mesomorphs were muscular and athletic.
  • Endomorphs were squatter and more overweight.
  • Ectomorphs were taller, narrower, and skinnier.

You aren’t supposed to fall neatly into one category. Most people have aspects of all three. There’s nothing inherently wrong here. Not yet.

The etymology of the word ectomorph is especially interesting. The prefix “ecto” refers to the “outside” of our bodies, our endoderms, our skin. Ectomorph is a more sophisticated way of calling someone “skinny.”

The Fall From Grace

Skinny people exist. Some guys do indeed have narrower frames. But Sheldon’s goals were somewhat more nefarious than that. He wanted to link body types with personality types:

  • Mesomorphs were bold and adventurous.
  • Endomorphs were friendly and lazy.
  • Ectomorphs were introverted, anxious, and intellectual.

Sheldon was never able to prove a connection. Moreover, he was criticized for stereotyping people based on their appearance. The somatotypes were pseudoscience right from the very beginning. They still are.

The Revival of the Ectomorph

Words aren’t static. Once they’re released into our culture, their meaning changes and evolves. My favourite example of this is how the word “awful,” originally meaning “full of awe” or “worthy of fear and respect” has gradually come to mean “very bad.”

“Ectomorph” is no different. Once it was ousted from the scientific community, the bodybuilding community caught hold of it. They dropped the personality stuff. They didn’t need it. They had muscles.

In the bodybuilding community, ectomorph came to refer to someone with a narrower frame, thinner bones, and a propensity for being thinner. There’s nothing pseudoscientific about that. Those traits do exist. Sometimes they combine together.

Nowadays, if someone calls themself an ectomorph, chances are they’re using bodybuilding slang, not old psychological pseudoscience.

Should We Call Ourselves Ectomorphs?

As a skinny guy, I had a really hard time building muscle. None of the conventional fitness advice seemed to be written for me. None of it worked. I couldn’t gain weight no matter what I tried.

Then I learned about the term “ectomorph.” It was one of my greatest discoveries. I started finding advice for people who were underweight and struggling to bulk up. I found a community of guys all battling against their skinniness.

Before/after photo of Shane Duquette starting skinny, bulking up, and building muscle.

As I was gaining weight, I blogged about it, and I used the term “ectomorph” to describe myself. I wasn’t talking about how I was anxious or introverted. I was anxious and introverted, but that was just a coincidence. I was using it to describe my natural skinniness.

This was ten years ago, back before the online fitness community had really taken off. Seeing a skinny guy blogging about gaining weight was rare. The blog took off, so I started spending my evenings helping my readers build muscle.

Jared's before and after progress photos showing him going from being a skinny ectomorph to being muscular.

That was around the time I helped my skinny roommate bulk up. Jared was 6′ and 130 pounds—similar to my starting height and weight. He was running into a number of health issues, too. His posture was crumbling. His tendons were giving out.

As our blog continued to grow, we teamed up with a world-class strength coach, Marco Walker-Ng:

Before and after photos of a skinny guy bulking up and becoming muscular

Marco had a degree in health sciences (BHSc), he was a certified strength and nutrition coach, and he’d interned with Eric Cressey (the strength coach for the New York Yankees). When we got in touch with him, he was helping his university football team bulk up, coaching a few professional athletes, and training some of our Canadian Olympic rugby team.

Photo showing a skinny ectomorph bulking up and becoming muscular from doing the Bony to Beastly Program.

The three of us teamed up to create our Bony to Beastly and Bony to Bombshell programs, and we got to work helping skinny people bulk up, both through our blog and through our programs. Using our own experience, training, and research, we were able to consistently help skinny guys build muscle.

Before and after photo of a woman gaining weight.

Then a funny thing started happening. People would come to our blog, see that we were using the word “ectomorph,” and accuse us of using pseudoscientific terminology to describe ourselves. That confused us.

Should we stop using the word ectomorph? Should we call ourselves “skinny” instead? Both words are slang terms for thin people. And they both describe different aspects of being thin.

The Difference Between Ectomorphs & Skinny Guys

We could call ourselves skinny, but not for long. As soon as we start bulking, we stop being skinny. We become thin, then fit, then athletic, and then strong. Having a narrow bone structure doesn’t prevent us from building muscle. We tend to build muscle quite quickly. And yet our bone structure remains the same. We’re still “ectomorphs.”

When someone gains weight quickly, is it muscle or fat?

That’s where the term ectomorph comes in handy. Even after going from 130 to 200 pounds, even after filling out the sleeves of large t-shirts, I’m still an ectomorph. I still have trouble gaining weight. I still lose weight if I get stressed, sick, or go on vacation.

The same is true in reverse. Some guys are naturally overweight and then slim down. They aren’t naturally skinny, they don’t have meagre appetites, and they don’t have trouble gaining weight. They’re skinny, yes, but for a completely different reason. Their struggles and goals are almost the exact opposite of ours.

With different genetic propensities, we benefit from different methods:

  • Intermittent fasting is designed to help people eat fewer calories. It’s not for us. Most of us have an easier time building muscle when we eat more often.
  • Keto diets are designed to help people eat fewer calories. Again, it’s not for us. Most of us have an easier time eating bulking diets rich in nutritious carbohydrates, such as whole grains, fruits, tubers, and legumes.
  • Strength training is designed to make people stronger for their size. That’s great, but most of us want strength and size! We’re better off doing hypertrophy training.
Illustration of a skinny guy eating a big nutritious bulking diet to build muscle and gain weight.

Is There an Ectomorph Diet?

Most people are trying to eat less without being devoured by their cravings. We’re trying to eat more without feeling perpetually full. These are opposite goals that require different methods.

  • More protein: we want to eat at least 0.7 grams of protein per pound bodyweight per day.
  • More calories: When actively bulking, we want to eat about 250–500 calories more than usual, allowing us to gain 0.5–1 pound per week.
  • More carbs: many overweight people find it easier to control their weight when restricting carbs. Most skinny guys are the opposite. We have an easier time gaining muscle and strength when we eat more carbs. Fruits, vegetables, legumes, and whole grains are rich in fibre, micronutrients, and phytonutrients. They swell our muscles with glycogen, improving our performance. The nitrates give us fuller muscle pumps and speed up muscle growth (study). Carbs are a powerful ally.
  • More snacks: every time you eat a balanced meal, you feed your muscles protein and energy. That’s why most muscle-building experts recommend eating 4–7 meals per day. Eating smaller meals more often also helps us overcome our smaller stomachs.
  • More liquid calories: when we drink our calories, they aren’t as filling, and they digest more quickly, making it easier to gain weight. That’s the opposite of what the average person wants. But for us, it’s a godsend. That’s why we benefit from drinking milk, milk alternatives, smoothies, protein shakes, and maybe a mass gainer.
  • Energy-dense foods: some foods are denser sources of calories than others. For people struggling to eat enough calories, it can help to lean into denser whole foods, such as trail mix, rice, ground meat, and bulking smoothies.

Is There an Ectomorph Workout?

Most people know resistance training is the best way to stimulate muscle growth. Bodyweight training and resistance bands are fairly popular, and they can work, but weight training is popular for a reason. Lifting weights is the simplest, fastest, and easiest way to build muscle.

Illustration of a skinny guy bulking up and building muscle.

Most beginner programs are designed to make you stronger for your size. Consider programs like Starting Strength, StrongLifts 5×5, or GreySkull LP. Even workouts marketed towards people who want to bulk up are often designed for overweight people trying to get leaner, not skinny guys trying to bulk up.

There’s a whole mythology surrounding strength training, too. Bodybuilding makes you big and fluffy, whereas strength training makes you hard and dense. None of that’s true. The muscles we build with strength or hypertrophy training look and feel exactly the same.

Hypertrophy has its own mythology. Ask most guys who started off thin, and they’ll preach the benefits of hypertrophy training. It’s the best way to get bigger and stronger, whereas strength training will only make you bigger for your size. It gets more interesting when we look at the subtext:

  • Strength training is for people who are too big and too soft. It’s to help them get denser and harder.
  • Hypertrophy training is for people who are too small and weak. It’s to help them get bigger and stronger.

So what makes an “ectomorph workout” unique is that it’s designed for someone who wants to get bigger and stronger. There’s no unique physiology we need to work around, we just need a workout program designed to help us accomplish our goals.

  • Start each workout with big compound lifts for your bigger muscles. Think of exercises like squats, bench presses, deadlifts, overhead presses, chin-ups, and rows. If you’re still a beginner, start with beginner variations of those lifts.
  • Add isolation lifts for your smaller muscles. Train your arms if you want bigger arms. Train your neck if you want a thicker neck. Do lateral raises to broaden your shoulders. Add in some planks and crunches if you want thicker abs. Add in some extra chest flys if your chest is lagging.
  • Get almost enough rest between sets. With 2–3 minutes of rest, you’ll have recovered most of your strength, especially if you’re still relatively thin. That tends to be long enough. Rest for longer if you need to.
  • Lift close to muscle failure. Go all the way to failure sometimes. Take some of your isolation exercises all the way to failure to learn what it feels like. Try to stop just shy of that on most of your sets.
  • Do enough sets per muscle per week. If you’re doing a full-body routine, that means training your muscles 3x per week, doing 4–8 sets for each muscle every workout.
  • Lift in a moderate rep range most of the time. Anywhere from 4–40 reps per set stimulates muscle growth quite well. However, the extreme ends of that rep range are somewhat situation. 4-rep sets suit deadlifts quite well. 40-rep sets are good for masochists who want to feel like they’re burning in Hell. Most of the time, doing 6–15 reps per set works better.
Illustration of a skinny guy doing deadlifts to build a thicker back.

Should Ectomorphs Avoid Cardio?

The idea is that ectomorphs are already struggling to eat enough calories. Cardio will only burn more. And that’s true. Cardio burns calories. But not very many. Plus, it tends to improve digestion and increase appetite. There’s no need to fear it.

Cardiovascular exercise is important for everyone. Everyone benefits from having a strong heart, a robust vascular system, and powerful lungs. Even ectomorphs.

If you’ve just started lifting weights, it’s okay to focus on lifting for a few months. You don’t need to add everything all at once. But once you’re in the habit of lifting weights and finishing up your first bulk, consider adding some cardio to your lifestyle.

If you’re new to cardio, even going on walks can work wonders on your health. Maybe that means going on a 30-minute walk most mornings. It’s okay to ease into it.


The word “ectomorph” has shady origins. It’s pseudoscience in psychological circles. But words evolve. Ectomorph is almost never used to refer to someone who’s introverted, anxious, and intellectual. Nowadays, it’s mainly used to describe naturally skinny guys. That’s fine.

Over the past few years, we’ve started calling ourselves “naturally skinny” instead of referring to ourselves as “ectomorphs.” It communicates the same thing but with less baggage, and we’ve found that fewer people get confused by it.

Still, it’s handy to have a term that describes us, encompassing our struggles. It’s still the dominant term for naturally skinny guys in many bodybuilding circles. I can see why. It’s useful. We tend to have different goals, and we tend to benefit from different diets and training styles.

Photo showing the Bony to Beastly Bulking Program for Skinny and Skinny-Fat Guys

Alright, that’s it for now. If you want more muscle-building information, we have a free bulking newsletter for naturally skinny guysIf you want a full foundational bulking program, including a 5-month full-body workout routine, diet guide, recipe book, and online coaching, check out our Bony to Beastly Bulking Program. Or, if you want a customizable intermediate bulking program, check out our Outlift Program.

Shane Duquette is the founder of Outlift, Bony to Beastly, and Bony to Bombshell, each with millions of readers. He's gained seventy pounds and has over a decade of experience helping more than ten thousand naturally thin people build muscle. He also has a degree in design, but those are inversely correlated with muscle growth.

Marco Walker-Ng is the founder and strength coach of Outlift, Bony to Beastly, and Bony to Bombshell. He's a certified trainer (PTS) and nutrition coach (PN) with a Bachelor's degree in Health Sciences (BHSc) from the University of Ottawa. He has over 15 years of experience helping people gain muscle and strength, with clients including college, professional, and Olympic athletes.