Illustration showing a skinny ectomorph flexing his lanky arms.

What’s An Ectomorph? Are They Even Real?

Is “ectomorph” a real term? Is it a real thing? Is that an accurate way to describe a naturally skinny person with a tall, narrow build who has a hard time gaining weight? These are surprisingly controversial questions, it’s a controversial word, and over the past ten years, we’ve gotten a lot of flack for using it. And I understand why, too.

It’s true that the word “ectomorph” is rooted in the bogus science of William Sheldon. But it’s also clear that different people have different struggles, and their struggles are often rooted in their genetics. Some people find themselves gradually growing overweight, whereas other people find themselves thin as rakes. Why is that?

You’ll also find a lot of questionable ads advertising an “ectomorph diet” or an “ectomorph workout.” They might claim that endomorphs need intermittent fasting, whereas ectomorphs need to eat more carbohydrates. Or that endomorphs need more cardio, whereas ectomorphs should eschew it. That’s questionable, yeah. But at the same time, should we really be telling the skinny guy who’s trying to gain fifty pounds of muscle to eat the same diet as the overweight person who’s trying to lose a hundred pounds of fat?

So, what is an ectomorph? Is it a real term? Is there a better word to describe naturally skinny guys? And how should we be eating and training to accomplish our rather rare goal of wanting to bulk up?

Before and after illustration of an ectomorph's progress as he gains muscle.

Video Version

If you prefer watching a video to reading an article, we’ve got you covered. I go over the history of the word “ectomorph,” as well as debunking the common complaints you’ll hear from other hypertrophy experts like Jeff Nippard, Dr. Mike Israetel, and Natural Hypertrophy.

To be totally clear, I love all of those channels. In fact, Jeff Nippard has my favourite YouTube channel of all time. But disagreeing with good arguments is far more interesting than disagreeing with bad ones, and there’s far more to be learned that way.

If you’d prefer to read, read on!


There’s a funny thing going on in the fitness industry. Even with weight training, there are different lifting niches, right? There are the CrossFitters, the powerlifters, and the bodybuilders. But there’s also a rift within those niches. Some guys like classic, time-proven methods, whereas other guys like data-driven, evidence-based guidelines. You can hear it in how they talk. “Steve Reeves used this routine” and “5×5 routines have been around for decades” are the classic group. These are the programs like Starting Strength and StrongLifts 5×5.

“The most comprehensive meta-analysis to date shows that this method is better” and “biomechanically, this lift does a better job of stimulating the chest” are the research-driven group. These are the programs like… well… ours, I suppose. Our methods are fairly conventional and classic, but we also go to great lengths to keep abreast of the hypertrophy research and evolve our methods along with it. In this same niche, there’s also Stronger by Science for powerlifters and Built With Science for the average person trying to build muscle.

That’s where the rift comes about. People have been colloquially talking about “ectomorphs” ever since the 1940s. They use it as an easy way to refer to someone with a small bone structure who’s naturally skinny. But it isn’t a scientific term. At least not anymore. You won’t find it in hypertrophy studies. Yes, you might hear published hypertrophy researchers talking about “ectomorphs” and “endomorphs” when they’re talking casually. For instance, in this article, the leading hypertrophy researcher Brad Schoenfeld, PhD, talks about how ectomorphs often need to eat more calories. But it’s not like you’ll find him referring to ectomorphs in his research papers. It’s just a colloquial term he uses.

As a result, we’ve dunked ourselves in a boiling pot of water. We talk as if we value science, but then we also use unscientific slang like “ectomorph” to talk about ourselves. That confuses some people. It can sound like we believe in somatotype psychology research or something. And we don’t. So let’s talk about that research for a second.

What is An Ectomorph?

The term “ectomorph” was coined by William Herbert Sheldon. It was part of his somatotype taxonomy that he used to divide men into three distinct body types: mesomorphs, endomorphs, and ectomorphs. What’s kind of cool is that the word “ectomorph” is named for the ectoderm—our skin. So “ectomorph” literally means “skinny.”

These three body types go like so:

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

Looking at that, I mean, there’s nothing much to argue with. Some people are naturally more muscular, others are naturally more overweight, and others are naturally thinner. Most people are some combination, and that’s fine—his system accounts for that. People can be 30% mesomorph, 50% endomorph, and 20% ectomorph.

Illustration of the skinny ectomorph hardgainer body type.

So very simply, an ectomorph is a naturally skinny guy with a smaller bone structure. We do exist. And I know that ectomorphs exist with 100% certainty because the term describes me absolutely perfectly. So at the very least, there’s one of us.

But this whole somatotype thing gets weirder.

The Somatotypes Were Indeed Debunked

Some people are naturally more overweight, some are naturally more muscular, some are naturally thinner. That makes sense. There’s no problem yet. Different body types. Fine. But Sheldon wasn’t just trying to divide people into three body types, he was also trying to prove that each body type had its own distinct personality type:

  • Mesomorphs are purportedly bold and adventurous.
  • Endomorphs are friendly and lazy.
  • Ectomorphs are introverted and anxious.

As you can probably guess, this didn’t wind up being true. He tried to advance this idea, but his psychology research was eventually disproven and has fallen out of use. Nobody is really pursuing this idea anymore.

So does that mean that “ectomorph” is a bunk term? Yes and no. It depends what you mean when you use it. Are you talking about someone with a thin bone structure who has trouble gaining weight? That’s fine. In that case, it’s just a slang term for a skinny person.

But if you’re talking about how skinny people are introverted and anxious, well, then, yeah, that’s a problem. There’s no good science to back that up. It’s just a common stereotype.

Are “Ectomorphs” Real?

Now, it just so happens that I’m a tall (6’2), have narrow bones (wrist size of a 5’4 man), and I’m a naturally skinny guy. In my early twenties I weighed 130 pounds, giving me a BMI of 16.7, which is severely underweight. And when I tried to bulk up, I had a lot of trouble. I found it almost impossible to gain weight. I’m what you might call a naturally skinny guy with a slender bone structure. But that’s a mouthful. So I wouldn’t blame you for using a much simpler term: ectomorph.

In fact, when I first started trying to build muscle, learning the term “ectomorph” was one of my greatest discoveries. I spent years of my life being confused about how to gain weight. But as soon as I started looking into advice for ectomorphs, I started finding advice written specifically for people who were underweight and struggling to bulk up.

Before/after photo of Shane Duquette starting skinny, bulking up, and building muscle.
Left: me at 129 pounds. Right: me at 193 pounds.

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 mean, I was anxious and introverted, but that was just a coincidence.

This was ten years ago, back before the online fitness community had really taken off. Seeing a skinny guy blogging about gaining weight was still quite rare. The blog took off, and 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—very similar to my starting height and weight. And he was almost as underweight as I was. He was running into a number of health issues, too, such as having tendonitis in both arms and a rapidly declining posture.

After we both succeeded at gaining weight, we realized that we could really help a lot of people by blogging about building muscle from a skinny “ectomorph” perspective. That was about the time 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 already gained over sixty pounds at under 10% body fat (naturally). But he’d also gotten a degree in health sciences (BHSc), all of his personal training (PTS) and nutrition (PN) certs, and he’d interned with Eric Cressey (the strength coach for the Yankees). When we got into touch with him, he was helping his university football team bulk up, he was coaching a few professional athletes, and he was training our Canadian Olympic rugby team.

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:

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

And then with our Bony to Bombshell program, we were helping naturally skinny women build muscle. Naturally thin women are often called “bananas” instead of ectomorphs, but the idea is the same.

Before and after photo of a woman gaining weight.

That was when a funny thing started happening. People would come to our blog, see that we were using the word “ectomorph,” and then say that we were a bogus site because we were using debunked terminology to describe skinny guys. That confused us.

Should we stop saying ectomorph? Should we start saying “skinny” instead? But that came with its own problems.

The Difference Between Ectomorphs & Skinny Guys

We could call ourselves “skinny,” but not for long. As soon as a so-called “ectomorph” starts building muscle, he isn’t skinny anymore. He’s a “naturally skinny guy with a thin bone structure who has trouble gaining weight,” but he isn’t “skinny” anymore.

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

That’s where the term ectomorph comes in handy. Even after gaining 65 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 they diet down to become skinny. They aren’t naturally skinny, they don’t have meagre appetites, and they don’t have trouble gaining weight. No, it took a lot of work for them to lose that weight. They’re skinny, yes, but for a completely different reason, and so their struggles and goals are almost the exact opposite of ours.

And then when it comes to the fitness industry, I mean, from an ectomorph’s perspective, it’s totally different. Intermittent fasting to help us eat fewer calories? Yeah right. Keto diets because carbs are making us fat? Nope. Strength training instead of hypertrophy training because we don’t want to get too “bulky?” No way! Bring on the muscle, baby!

So again, it’s useful to be able to talk about being ectomorphs. Most of us share a common goal. We want to build a ton of lean muscle, gain a bunch of weight, and avoid becoming skinny-fat.

Over the past few years, we’ve tried to say “naturally skinny” instead of “ectomorph.” It communicates the same thing but with less baggage, and we’ve found that fewer people get confused by it. But at the same time, it’s really handy to have a term that’s for us, that encompasses our struggles. It’s hard to abandon that ectomorph term, especially it’s still the dominant term for naturally skinny guys in a lot of bodybuilding and fitness circles.

Hardgainers, Non-Responders & the Dreaded Skinny-Fat

There are a few other terms that are useful for a naturally skinny guy to know, each describing a slightly different struggle that we tend to run into:

  • Hardgainer: someone who has a hard time eating enough calories to gain weight. This is the skinny guy who tries to bulk up but can’t budge the scale. We’ve written about hardgainers here.
  • Non-responder: this is someone who tries lifting weights but fails to make much progress. A lot of the time that’s because they’re a hardgainer, in which case learning how to eat more calories solves the problem. But some people respond better to lifting than others, and for a variety of reasons. With that said, at least in our experience, there’s very little overlap between non-responders and skinny guys. Most skinny guys build muscle very fast.
  • Skinny-fat: this is someone who doesn’t have much muscle mass (e.g. upper arms small than 13 inches) but also quite a lot of body fat (body-fat percentage over 20%). This isn’t a body type. It’s like saying someone is “out of shape.” But with that said, it’s harder for some people than others to become muscular and lean, and sometimes being skinny-fat can call for a less aggressive approach to bulking up. We’ve written an article for skinny-fat guys here.
  • Bulking: this is the concept of facilitating muscle growth by gaining weight. It’s somewhat of a controversial term among guys who aren’t naturally. After all, the average person is overweight. They want to lose a ton of fat and build a bit of muscle. We want the opposite: to gain a bunch of muscle and lose a tidbit of fat. For us, where we want to gain weight, we build muscle by “bulking.”
  • Dreamer Bulking: this is what happens when guys bulk too aggressively or ineffectually and wind up gaining a bunch of fat, becoming either chubby or skinny-fat.
  • Dirty Bulking: this when people bulk up by eating “dirty” foods, and it’s another one of those pseudoscientific sorts of terms. It’s true that bulking up on junk food doesn’t tend to work as well, but it’s not as simple as dividing everything into “clean” and “dirty” foods. Regardless, building a diet made up mostly of whole foods—around 80% or so—is still best.
  • Lean Bulking: lean bulking is when people bulk more slowly in an effort to build muscle more leanly. In our opinion, almost every bulk should be done with the goal of gaining mostly muscle. The rate that we bulk should depend on how quickly we can expect to build muscle leanly.

Now, you don’t need to use any of these terms, just like you don’t ever need to say “ectomorph.” And some of them are slang. You won’t find “bulking” in hypertrophy research, either. But even so, it’s a handy word to throw around when you’re talking about trying to build muscle as a naturally skinny guy.

Is There an Ectomorph Diet?

Okay, so here is where the terrain starts to get treacherous. As soon as we start talking about an “ectomorph diet,” people might assume that we’re saying that all naturally skinny guys benefit from eating the same foods, have the exact same goals, or have a unique physiology that requires a different approach to nutrition. That’s not true.

Illustration of a bowl of rice.

With that said, though, a lot of us share the goal of wanting to build muscle, which means that we need to eat enough protein. And most of us want to gain weight, which means that we need to eat enough calories to gain weight. And most of us have a hard time eating enough calories to gain weight. So that does mean that most of us ectomorphs want to eat in a different way from the average person:

  • More protein: we want to eat at least 0.8 grams of protein per pound bodyweight per day to allow for a maximal rate of muscle growth.
  • More calories: When we’re actively bulking, we want to eat about 250–500 calories more than we typically do, allowing us to gain 0.5–1 pound per week. That can be as simple as adding a glass of milk along with our meals or a snack of trail mix between meals, but it can also mean full calorie counting and macro counting. Then, it’s important to keep track of our weight gain over time, adjusting our calorie intake accordingly (which often means adding more calories into our diets over time).
  • More carbs: a lot of naturally overweight people find it easier to control their weight when they restrict their carb intake, sometimes even going so far as trying ketogenic diets. To build muscle, though, it usually helps to eat more carbs. And leaner guys who lift weights tend to respond particularly well to higher-carb diets. This is true for athletes, for bodybuilders, and for many (but not all) of us.
  • Eating more often: there’s nothing wrong with eating 2–3 meals per day for our general health or fat loss, and intermittent fasting is fine. But when we’re trying to build muscle, it helps to stimulate muscle-protein synthesis more often, and so it can help to eat 4–7 meals per day (including snacks). That can also make it easier to fit more calories into 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 great. That’s where milk, smoothies, protein shakes, and mass gainers comes in.
  • Bulking foods: some foods are denser sources of calories than others. For people who are struggling to eating enough calories, it can really help to lean into common bulking foods, such as trail mix, white rice, ground meat, and smoothies.

We could go on forever, but you get the idea. Most people are trying to find ways to lose fat without going crazy from cravings, whereas we’re trying to build muscle without feeling perpetually full. These goals are opposite of one another.

Illustration of a skinny hardgainer eating a feast in his attempt to bulk up, gain weight. and build muscle.

So do ectomorphs have a unique physiology that benefits from some trendy diet? No. But if we’re trying to build muscle and being limited by our inability to eat enough calories to gain weight, then, yeah, it can help to eat a so-called “ectomorph bulking diet.” But it depends on your situation and goals, not just on your bone structure.

Is There an Ectomorph Workout?

Just like with our diets, the type of workout we should do depends on our struggles and goals. Most men want to be strong and muscular, but most of them are coming at it from the other side: being overweight and wanting to chisel out their muscles. For us, we’re starting off skinny and trying to build that muscle mass from scratch. To do that, we should work out in a way that’s designed to stimulate maximal amounts of muscle growth.

Most people know that to best build muscle, we should do resistance training. And although both bodyweight training and resistance bands are fairly popular, most people realize that it’s easier to build muscle with weight training. Even then, though, it can get a bit confusing.

Illustration of a man doing a low-bar barbell back squat.
The main strength training lift: the low-bar back squat.

Most beginner programs are best defined as strength training programs. This includes Starting Strength, StrongLifts 5×5, GreySkull LP, and almost all of the popular beginner weight training programs. They tend to be rooted in the sport of powerlifting, use lower rep ranges, and focus primarily on getting stronger at the back squat. We get a lot of people coming to us after doing these programs, confused about why most of their gains are in their thighs and hips. It’s because in most of these programs, squats are done twice as often as any other lift.

There’s a whole mythology surrounding strength training, too. About how training for strength is more practical, that bodybuilders are just big and fluffy, and that lower rep ranges build harder, denser muscles. None of that is true. The muscles we build with strength training and hypertrophy training look and feel exactly the same. The difference is that hypertrophy training makes it easier to build more muscle mass, whereas strength training is optimized for making neural gains, improving our coordination and thus making us stronger for our size.

Even when it comes to “being strong” the difference between strength and hypertrophy training is nebulous. It’s just the difference between favouring maximal strength vs strength endurance. The powerlifter who can bench 315 pounds for a single and 225 for 10 reps is comparably “strong” to the bodybuilder who can bench 300 for a single and 225 for 15 reps. Yes, the powerlifter can bench more for a single, but the bodybuilder can get more reps. But both of them have a big 1-rep max and can get a lot of reps with 225. They’re both strong, just with slightly different specialties.

Illustration of a skinny ectomorph doing the bench press with long arms and a thin ribcage.

Anyway, what I’m trying to say is that most weight training programs aren’t designed to make people bigger and more muscular. And the ones that are—the bodybuilding programs—are often designed for people who are already quite big. So what makes an “ectomorph workout” unique is that it might be a hypertrophy training program for a guy who’s still fairly skinny and new to lifting.

And in our experience, most skinny guys don’t come to us wanting to pack most of their muscle mass into their thighs, hips, and lower back so that they can improve their 1-rep max on the low-bar back squat as quickly as possible. Most of us are eager to build broader shoulders, bigger chests, bigger upper backs, and to bulk up our skinny arms. Does that mean that we shouldn’t include squats or deadlifts in our workout routines? Of course not! Those are great lifts. And it’s not like we want our legs to stay skinny.

Illustration of a skinny ectomorph doing a deep dumbbell goblet squat.

But we might not start every single workout with squats. And when we do squat, we might choose different variations, such as choosing goblet squats for beginners, and then progressing to front squats. Not only are those better lifts for stimulating lower-body muscle growth, but they’re also easier on our joints over time, and they’re great for building muscle in our upper bodies.

Before and after illustration of a man with a skinny neck building a muscular neck.

So is there such a thing as an ectomorph workout? Kind of. But it’s not that we have a unique physiology that demands we lift weights in a bizarre way. It’s more that skinny guys are eager to build muscle, gain weight, bulk up lanky arms, and build thicker necks. It’s a difference of goals and struggles. But even for us, the best way to build muscle is fairly conventional hypertrophy training:

  • Big compound lifts for your bigger muscles, such as your chest, upper back, butt, and shoulders. Think of the squat, bench press, deadlift, overhead press, chin-up, and row. And if you’re still a beginner, start with beginner variations.
  • Isolation lifts for the smaller muscles, such as biceps curls for your biceps, skullcrushers for your triceps, curls and extensions for your neck, and perhaps some crunches or planks for your abs.
  • Long enough rest periods that we’re limited by our muscles more than our cardiovascular systems. Resting 2–5 minutes between sets often works well. (And then you can do cardio on the side, if you want. It’s great for your health, and there’s no reason ectomorphs shouldn’t do cardio. In fact, we’re often quite good at it.)
  • Lifting close enough to failure to truly challenge your muscles, provoking muscle growth. That often means taking some sets to failure so that you learn what failure feels like, and so that you see how far away from it you’ve been stopping.
  • Doing enough challenging sets per muscle, per workout, and per week. For skinny beginners, 3 full-body workouts per week tends to work well, doing a few sets for each major muscle group each workout. Then, as you get more advanced, you can divide up your training over more days if you want to (although I’ve gained 65 pounds without ever needing to).
  • Do most of your lifting in the so-called “hypertrophy rep range,” somewhere between 6–20 reps per set. That might mean 6–10 reps for your bigger compound lifts, such as squats and deadlifts, 8–15 reps for your secondary lifts, such as biceps curls and triceps extensions, and 12–20 reps for smaller lifts, such as neck curls and lateral raises.

If you want a program that puts all of this together—a 5-month workout routine, video tutorials teaching all of the lifts, a full diet guide, a recipe book, and a yearlong membership in our coaching community—I think you’d like our Bony to Beastly Program.

But whatever program you use, just remember that the main thing is getting started, being consistent, always striving to outlift yourself, and pivoting whenever something isn’t working. Even with bodyweight training or strength training, you can still build muscle, it’s just a bit harder and/or slower. The most important thing is getting started and building good habits.


The somatotypes, as defined by William Sheldon, are bogus. His hypotheses were disproven. However, that doesn’t mean that we can’t refer to ourselves as ectomorphs when we’re talking about being naturally skinny guys with thin bone structures. In that case, we’re not using it as a scientific term, we’re just using it as a slang term to describe our situations, struggles, and goals.

Illustration showing an ectomorph as he builds muscle, going from skinny to muscular.

And, of course, it’s always good to point out that not everyone is exactly the same. Some ectomorphs have broader shoulders, naturally higher body-fat percentages, barrel-shaped rib cages, bigger appetites, or are shorter. It’s a very loose term. I just so happen to be an ectomorph in almost every sense, but most people only have a few of the traits.

Finally, if you want to learn from our experience, you might have better luck calling yourself “naturally skinny” when you talk about this stuff with other people. If you use the term “ectomorph,” you might get people saying: “no, no, that term is stupid. Don’t you realize that not all skinny people are anxious and introverted? And just because I’m fat that doesn’t mean I’m lazy!” And they’d be right. But that probably wasn’t what you were trying to say.

Anyway, what do you guys think? How do you, as a naturally skinny guy, feel about us using the term “ectomorph”?

Shane Duquette is the co-founder and creative lead of Outlift, Bony to Beastly, and Bony to Bombshell, and has a degree in design from York University in Toronto, Canada. He's personally gained sixty pounds at 11% body fat and has nine years of experience helping over ten thousand skinny people bulk up.

Marco Walker-Ng is the co-founder and strength coach of Outlift, Bony to Beastly, and Bony to Bombshell, and is a certified trainer (PTS) with a Bachelor's degree in Health Sciences (BHSc) from the University of Ottawa. His specialty is helping people build muscle to improve their strength and general health, with clients including college, professional, and Olympic athletes.