Growing up as a naturally skinny guy can be confusing. We’re living right in the middle of an obesity epidemic, surrounded by people who gain weight by accident, and yet no matter what we do, we can’t budge the scale. Why are we immune to weight gain?
Do ectomorphs really have faster metabolisms and smaller stomachs? Or is it something more nefarious? I remember wondering if I had some sort of leaky gut syndrome that was preventing me from gaining weight.
In this article we’ll cover:
- Do ectomorphs have faster metabolisms?
- Do ectomorphs have smaller stomachs?
- Why do hardgainers resist gaining weight while overfeeding?
- Do skinny guys have better insulin sensitivity and carb tolerance?
- What’s the best ectomorph bulking diet?
“One of his volunteers, for example, began at 132 pounds. He struggled resolutely for more than thirty weeks to gain weight, ate great amounts of food, and reduced his activity to less than half its former level, but was never able to push above 144 pounds. He simply didn’t have the willpower to get fat.”
It’s well-documented that some people have a hard time gaining weight. There are a few different terms for it:
- An ectomorph is someone with a thin body type
- A hardgainer is someone who doesn’t gain weight in a calorie surplus
- A non-responder is someone who doesn’t build muscle when lifting weights
However, most of those terms overlap with one another. For example, having thinner body type usually makes it harder to gain weight in a calorie surplus, which then makes it impossible to build muscle while lifting weights. They all describe the same phenomenon.
Here’s what’s happening:
- Skinny guys have smaller stomachs and faster metabolisms (ectomorph)
- Being skinny increases insulin sensitivity and makes it harder to overeat (hardgainer)
- Having a smaller stomach makes it harder to get into a calorie surplus (hardgainer)
- Having a faster metabolism makes it harder to gain weight in a calorie surplus (hardgainer)
- If you can’t eat enough calories to gain weight, you won’t build muscle while lifting weights (non-responder)
If we can figure out how to bulk up with a small stomach and a fast metabolism, then we’ll be able to gain weight, and all of our problems will disappear. Best of all, having a fast metabolism and being insulin sensitive is a genetic advantage that will help us stay lean and healthy while bulking up. We can maintain those genetic advantages while building muscle.
Thing is, bulking up as an ectomorph just requires a different approach. It’s a rare body type, so it’s rare to find a diet designed for ectomorphs. In fact, we’ve had to reverse engineer our ectomorph bulking diet from research conducted on overweight people.
Ectomorphs are designed to burn calories
According to the Smithsonian, there’s an evolutionary reason why ectomorphs burn more calories. If you’re trying to run a marathon across the plains of Africa, being an ectomorph helps quite a lot. If you watch the summer Olympics, this will come as no surprise, as ectomorphs—especially those from places like Kenya—absolutely dominate the long-distance races.
People with thin builds evolved to be good at travelling long distances in hot climates, radiating their energy outwards to avoid overheating. To do this, we evolved smaller stomachs, faster metabolisms, lighter bones, longer limbs, and less body fat to insulate us.
Then, if you look at populations who evolved in Northern climates, such as the Inuit, you’ll notice that they tend to be shorter and thicker. The Smithsonian argues that this is because endomorphs, with their thicker builds, are good at conserving heat and hibernating, making them great for surviving harsh arctic winters.
Our body types evolved for different purposes, giving us totally different strengths and weaknesses:
- Ectomorphs burn calories to keep them lean, light, and cool.
- Endomorphs conserve calories to stay chubby, insulated, and warm.
If you’re curious about how much of an ectomorph you are, here are the three tests that researchers use to measure bone structure and body type. Even if you’ve got an extremely ectomorphic bone structure, though, it’s hardly a limitation. We can’t change our bone structure, but we can build muscle on top of it.
Ectomorphs have far smaller stomachs
Whenever I would try to eat more calories, I always felt bloated, sick, and lethargic for hours afterwards. Worse still, after a few weeks of trying to eat more, I started getting acid reflux. My stomach just wasn’t big enough to handle large meals.
It turns out that stomachs come in different sizes. In his famous 1945 study, AJ Cox found that the size of the human stomach varies by up to 600% between individuals. In fact, according to Cunningham’s Textbook of Anatomy, “no organ in the body varies more in size than the stomach.” This means that another guy the same height as you may have a stomach six times as large.
There’s a fairly simple explanation for why ectomorphs tend to have smaller stomachs. Ectomorphs have narrower torsos and shallower rib cages, which leaves less room for our organs. Our other organs have fairly fixed sizes, though, so our stomachs wind up seeing the greatest reduction in size.
It’s easy to see how having a smaller stomach could make it harder to gain weight. That bears out in the research, too. A 2001 study showed that the smaller someone’s stomach was, the fewer calories they were able to consume per meal, and the less they were likely to weigh.
It’s no wonder we can’t “just eat more.” Our stomachs aren’t big enough… yet.
What’s interesting, though, is that unlike our ectomorph bone structure, we actually have a bit more control over our stomach size. In another study, researchers recruited participants and split them into two groups. One group ate their normal diet, whereas the other group was forced to eat extremely small meals. Four weeks later, the stomachs of the people who were eating the tiny meals shrunk by as much as 36%. The researchers concluded that stomach size can adapt over time.
This suggests that by gradually eating larger and larger meals, you can increase your stomach size. This certainly lines up with my personal experience. After gaining sixty pounds of muscle over the course of a couple years, my stomach got bigger, allowing me to comfortably eat larger meals. That helped me to intuitively maintain my higher body weight.
That doesn’t help us when we’re trying to bulk up, though. Ectomorphs still start this journey with too-small stomachs.
Ectomorphs have great insulin sensitivity
If you’re a naturally skinny-fat ectomorph, your insulin sensitivity is likely what differentiates you from a naturally leaner ectomorph. You can ignore this section and read our article for skinny-fat guys instead.
If you’re a lean ectomorph, though, one muscle-building advantage that you have is your insulin sensitivity (study). Having great insulin sensitivity is a genetic advantage that’s associated with numerous health benefits, including the ability to gain muscle leanly. However, as you might be able to guess, it can also make it harder to gain weight. And if you can’t gain weight, then you won’t be able to build muscle.
Here’s a quick primer on how insulin works:
- When your insulin levels are low, you’ll get hungry.
- When you eat, your insulin levels will go up, and you’ll feel full.
As soon as you’ve eaten enough food to maintain your body weight, it becomes extremely unpleasant to continue eating extra calories. For an ectomorph, fullness is no joke. Because of how insulin sensitive we are, fullness is a very strong signal. Overeating can be extremely hard.
This is totally different from the average person. By the time the average person feels full, not only have they produced too much insulin, they’ve already eaten too much food. And their fullness ramps up so slowly and tepidly that it’s easy to ignore. It’s not a powerful signal. It’s easy to override. If the average person wants to gain weight, they can just do it. It’s easy.
To be clear, insulin is part of your body’s bodyweight regulation system. The whole purpose of that system is to keep you weighing the same amount day after day, year after year. Insulin is supposed to make it hard for you to gain weight. It’s everyone else who’s broken, not us. The problem is, if you’re currently underweight, as many ectomorphs are, then it’s important to gain muscle. Being insulin sensitive can make that much harder.
However, insulin has another role. Insulin also affects what kind of weight we gain while bulking:
- If your fat cells are more insulin sensitive, you’ll gain more fat
- If your muscle fibres are more insulin sensitive, you’ll gain more muscle
When we talk about having “great” insulin sensitivity, we mean that your system is working properly, and that if you’re following a good bulking workout program, then your muscle fibres will become more insulin sensitive, and you’ll be able to gain muscle more leanly:
Now let’s say that you succeed in bulking up, gaining a bunch of lean muscle mass. At that point, your insulin sensitivity will get even better:
- Heavy weightlifting increases insulin sensitivity (study)
- Gaining muscle mass increases insulin sensitivity (study)
So if you already have great insulin sensitivity, building muscle is only going to help. It’s going to further improve your health, and it’s also going to help you maintain your bigger, more muscular body. After all, your bodyweight regulation system will gladly help you maintain a strong, healthy physique. That’s what it’s designed for.
This is one of the reasons why ectomorphs bulk so aggressively, building muscle so quickly and leanly. (Here’s our article about how quickly you can expect to gain muscle and strength while bulking.)
Ectomorphs hit the genetic jackpot with insulin sensitivity, and we want to hold onto it at all costs. However, it also means that we aren’t about to overeat by accident, and when we try to overeat on purpose, it can be damn hard.
Ectomorphs do have faster metabolisms
Many of us ectomorphs feel like caloric bottomless pits. No matter how much food we shovel into our mouths, our weight refuses to budge on the scale. Why is that? Are our metabolisms really that much higher?
Some experts argue that we’re just underestimating how much we eat. That could make sense. After all, we have smaller stomachs that limit our meal size combined with insulin sensitivity that makes us feel full more quickly. For some ectomorphs, that may explain the mystery.
However, we’re also naturally thinner, which gives us a greater surface area, causing us to burn extra calories compared with shorter and thicker people. This phenomenon is called Allen’s Rule, based on the scientist who discovered it.
That also explains part of the mystery.
The mystery is far more interesting than any of that, though. Scientists started noticing strange things happening during overfeeding studies, where they were trying to study fat gain.
In one study, the participants were overfed by 1,000 calories per day for eight straight weeks and instructed not to exercise. Eight weeks later, most people had gained quite a bit of fat, with one guy gaining a whopping 9.3 pounds. That’s fairly normal, and it’s exactly what they expected. You overeat, you get fat.
However, there were also a couple participants who hardly gained anything, with one guy only gaining 0.79 pounds. This was a puzzling result, so they came up with a name for these superhuman creatures: “hardgainers.”
Hardgainers remained a mystery for quite a while, until a group of researchers discovered that hardgainers burn extra calories through subconscious activity—things like fidgeting and postural control (study).
While this may not sound like a big deal, the effect is enormous. Hardgainers burn 50% more calories than the average person while just sitting in a chair, and when they stand up, they start burning 80% more calories (study).
Depending on how much of your time you spend standing, that works out to burning an extra 600–950 calories each day.
That’s already a huge difference, but it’s not even the whole story…
As it turns out, hardgainers also choose to spend about two extra hours on their feet each day (study), burning another 350 extra calories.
To put this into perspective, the average guy might be able to maintain his weight with 13x his bodyweight in calories each day. If he weighs 150 pounds, that’s about 2,000 calories per day. If he eats more than that, he might start getting fat.
However, some ectomorphs can eat 22x their bodyweight each day without gaining any fat. If he weighs 150 pounds, that’s 3,300 calories per day.
The interesting thing is that a hardgainer can maintain his weight on both caloric intakes. If a 150-pound hardgainers eats 2,000 calories per day, his metabolism will slow down and his weight will stay the same. If he starts eating 3,300 calories, you’d expect him to gain weight, but he doesn’t—his metabolism just revs up and burns the extra energy.
So that “just eat more” advice is pretty damn shoddy. Our metabolisms eagerly adapt to any attempts at overfeeding, making our bulking attempts feel totally futile.
Does that mean it’s impossible to bulk up? Luckily, we aren’t simply trying to gain weight, we’re trying to build muscle. With a good enough nutrition and weightlifting program this won’t much get in the way of building muscle.
When we stimulate muscle growth by following a good weightlifting program, eating enough protein, and eating enough calories, our bodies will shift our priorities. Instead of revving up our metabolisms to prevent fat gain, we’ll keep some of those extra calories to invest into muscle growth.
Calories that need to be invested into building bigger biceps aren’t extra calories, after all. Being a hardgainer makes us resistant to fat gain but not muscle gain.
So being a hardgainer doesn’t make it harder to eat enough calories to build muscle. Finally an ectomorph trait that isn’t working against us. Being a hardgainer just keeps our gains leaner. It burns off unneeded calories.
However, do keep in mind that there’s always a point where you’re eating so many excess calories that some will spill over into fat gains. We tend to get a pretty wide berth though, especially if we’re following a good lifting program and eating enough protein.
Ectomorphs lose their appetite when stressed
Our small stomachs, insulin sensitivity and fast metabolisms make it hard to eat enough on a good day. What about when we get tired, busy or stressed?
If we were most people, the worse our lifestyles got, the more weight we’d gain. But strangely, we have the exact opposite emotional response.
Eating food causes the release of dopamine, and that release of dopamine causes feelings of intense pleasure. This is how our bodies encourage us to do things that are good for survival and replication. Eating calories helps us survive, so our body associates eating calories with pleasure.
Not surprisingly, it’s pretty common for people to get bummed, tired or stressed and automatically turn to food, subconsciously craving that surge of dopamine. This is your typical scenario where the heartbroken gal drowns her sorrows in a tub or ten of Ben & Jerry’s.
First of all, because we’re so insulin sensitive (as explained above), our bony hearts are mendable with relatively small portions of ice cream.
Researchers call this a lower hedonistic response to food, i.e., we aren’t as likely to use food to seek pleasure. And so in tough times, we tend to find ourselves losing weight.
If you get in a fight with your gal, she might storm off and raid the fridge. Meanwhile, you might forget that the fridge even exists.
This applies to other “stressors” as well, such as weightlifting. Lifting heavy things makes most guys ravenous, whereas I’ve always found that it makes me less hungry.
According to a study published in Physiology and Behavior, while lifting causes most people to eat more calories, it makes other people eat fewer calories. This lines up with other studies as well, and seems especially pronounced when the type of exercise is heavy weightlifting (study, study, study).
This is one reason why most guys naturally grow bigger and stronger when they start lifting weights. Even if they weren’t already gaining weight by accident (i.e. getting fat), their bodies will automatically up-regulate their food intake when they start lifting weights.
We have a great fix for this one: drinking a calorie-rich blend of protein and carbohydrates while working out. Not only does it boost workout performance and make our gains leaner, it also makes it far, far easier to eat enough calories to build muscle. Here’s our workout shake recipe.
Ectomorphs can easily maintain muscle mass
I used to worry that even if I could build muscle, at some point I’d surely get sick, stressed or busy and then just lose it all again. I worried that as soon as I stopped overfeeding, my muscles would shrivel up and be skinny again.
Luckily I was dead wrong. Building muscle requires consuming a lot of extra calories (among other things), but maintaining muscle is entirely different.
As you bulk up, your stomach will grow bigger, making it easier and more enjoyable to eat bigger meals. Your digestive system will get better at digesting food, making you feel better while digesting those bigger meals. You’ll become even more insulin sensitive, making it even easier to maintain a low body fat percentage. You can cut your protein intake in half, meaning that you won’t ever really need to think about it again. And while building muscle will raise your metabolism a little bit… it’s not a big increase—not big at all.
A pound of muscle only burns around 6 calories per day (study, study, study), so gaining 20 pounds of muscle will only burn an extra 120 extra calories per day. That’s barely a 5% increase in your metabolism. That’s a small glass of milk, or a cookie for dessert.
Moreover, many of the changes in your muscle fibres are totally permanent. Once you build muscle, it becomes very easy to stay muscular. You’ll find that you’re just “naturally” stronger and leaner.
If you want to learn more about this, here’s our article about changing your set point.
How to eat enough calories to gain weight
Trying to eat enough to gain weight is a lot harder for ectomorphs than most people realize. Our stomachs can be up to six times smaller, our metabolisms can burn up to 1,300 extra calories per day, and as soon as we go into a calorie surplus, it can feel awful.
Thinking that “just eat more” is a good bulking strategy is like thinking the ultimate fat-loss secret is “just eat less.” If you told that to a fat person, he’d probably eat you, and rightfully so—that’s totally moronic advice.
So, as ectomorphs, how can we eat more calories?
Well, we’ve made a free guide for you. It includes our popular article about how to eat more calories, a sample bulking meal plan designed for ectomorphs (which is how I was able to finally gain 55 pounds), and we’ve even included 3 bulking recipes: one for breakfast, lunch and dinner.
You can get it (for free) right here:
Free guide: How to Eat More
- A PDF version of this article for later reference
- A cheat sheet of the main points (great for putting on your fridge)
- A sample meal plan with these principles optimized—the same plan Shane used to gain 55 pounds
- 3 of Shane's favourite bulking recipes; one for breakfast, lunch and dinner
Plus, we'll put you on the Beastly newsletter so that you get all of our best information and offers.