Illustration of a skinny hardgainer's stomach.

Why Is It So Hard for Skinny Guys to Gain Weight?

Struggling to bulk up as a naturally skinny “hardgainer” can be confusing. We’re in the midst 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 is it so hard for us to gain weight?

We’re skinny guys, too. When we first started trying to bulk, we failed to gain any weight, and so we failed to build any muscle. We each gave up several times before finally succeeding. After figuring out how to eat enough, Marco gained 63 pounds while getting his health sciences degree and training certifications, and then went on to help college, professional, and Olympic athletes bulk up. When I started blogging about my weight-gain attempts on my design blog, I was referred to Marco. With his help, I was able to gain 55 pounds in around two years, with our readers getting similar results. We then created a program that’s helped over 10,000 other skinny guys build muscle.

This is all to say that it’s hard to bulk up as a skinny guy, but it’s not impossible. In fact, we have a number of genetic advantages that can allow us to gain muscle more quickly and leanly than the average person. We just need to combine hypertrophy training with a proper bulking diet and a good lifestyle. If we can do that, we can build muscle, and we can build it fast.

In this article we’ll cover:

  • Do we really have faster metabolisms?
  • Do skinny guys have smaller stomachs?
  • Why do we resist weight gain?
  • What’s the best bulking diet?
  • What’s the best type of training for hardgainers?
  • Why stress management and sleep are so important.
  • How fast can hardgainers build muscle?
Before and after illustration of a skinny hardgainer ectomorph becoming muscular.

What’s A Hardgainer?

A hardgainer is, quite simply, someone who has trouble gaining weight. It applies to people who have trouble gaining fat, but it’s more commonly used to describe skinny guys who have a hard time bulking up.

The fact that hardgainers exist isn’t controversial. It’s well-documented that some people have a hard time gaining weight. Here’s a quote about Dr Ethan Sims, a famous researcher who conducted several overfeeding studies in the 70s (study, study):

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.

Ethan A. H. Sims, MD

However, even though “hardgainer” isn’t a controversial term, it is a confusing one. It’s often used interchangeably with a few other terms that describe skinny guys, such as ectomorph and non-responder. So here are some definitions:

  • Hardgainer: someone who has a hard time gaining weight. Not every hardgainer is naturally skinny or has a thin bone structure, but many of them do.
  • Ectomorph: someone with a thin bone structure. However, not every ectomorph has trouble gaining weight. It’s also worth noting that “ectomorph” isn’t a scientific term, it’s just used colloquially to describe a skinny body type.
  • Non-Responder: someone who doesn’t get a strong growth response from lifting weights. Not all non-responders are skinny. In fact, if we can eat enough, skinny people tend to get a fairly strong muscle-building stimulus from hypertrophy training.
Illustration of the skinny ectomorph hardgainer body type.

However, although these terms all mean different things, they do tend to overlap with one another. For example, having a thinner body type (being an ectomorph) usually makes it harder to gain weight (making us hardgainers), and failing to gain weight prevents us from building muscle (making us non-responders). So in that sense, they can all describe a skinny guy who’s struggling to bulk up.

Here’s what’s happening:

  • Having narrower “ectomorph” frames means that our stomachs are smaller, which makes it hard for us to eat enough to gain weight. Plus, having a thinner body type with less fat to insulate us causes us to radiate more body heat outwards, raising our metabolisms.
  • Having a higher “hardgainer” metabolism means that we need to eat even more calories in order to gain weight. But we have smaller stomachs. So where are we supposed to put those calories?
  • And then to add insult to injury, another feature of being a hardgainer is that our metabolisms tend to adapt quite quickly to higher calorie intakes, preventing us from gaining weight even when we do succeed at eating more.
  • If being an ectomorph or hardgainer prevents us from eating enough calories to fuel muscle growth, then we’ll have trouble gaining muscle size and strength when we work out, making it (falsely) seem like we have poor muscle-building genetics. This can get us labelled as “non-responders.”

So being an ectomorph often overlaps with being a hardgainer, which then makes us seem like non-responders. We aren’t really non-responders, though. We’ve coached nearly 10,000 guys through this. We can build muscle just fine. Here are some client examples, and here’s me after gaining sixty pounds:

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

If we can figure out how to overcome our small ectomorph stomachs and our fast hardgainer metabolisms, then we’ll be able to gain weight. And once we can gain weight, all of our muscle-building problems disappear. In fact, because of the law of diminishing returns, and because we’re essentially starting behind the starting line, skinny guys tend to be able to gain muscle faster than any other body type.

For instance, the average man starts off with around eighty pounds of muscle mass on his frame (source). A skinny guy might start off with half of that—forty pounds. However, our frames can hold similar amounts of muscle (give or take 10%), meaning that we’re starting off much further away from our genetic potential. This allows us to get explosive growth when we first start bulking up. We fill out quickly.

This period of rapid growth when people first start weight training is often called “newbie gains,” but keep in mind that anyone who is untrained can experience newbie gains. What makes our situation special is that we’re so far away from our genetic potential. We build muscle so quickly because our frames are capable of holding much more muscle mass than they’re currently holding.

Best of all, having a fast metabolism and being insulin sensitive can help us stay lean and healthy while building muscle, and those genetic advantages only become more exaggerated as we continue bulking up.

Bulking as a skinny hardgainer just requires a different approach. Thing is, it’s a rare problem, and so it’s rare to find a diet designed for hardgainers. In fact, we’ve had to reverse engineer our bulking diets from research conducted on overweight people.

To summarize, a hardgainer is someone who has trouble gaining weight. However, that doesn’t mean that hardgainers have poor muscle-building genetics. Quite the opposite—we’re often able to gain muscle more quickly than other body types.

Hardgainers 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. Ectomorphs—especially those from places like Kenya—absolutely dominate long-distance races.

Illustration comparing a skinny hardgainer against the average man.

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.

Diagram showing Allen's Rule.

One reason this happens is explained by Allen’s Rule, where lankier body shapes have a greater surface area, thus causing them to radiate more heat outwards. This is then further exaggerated because skinny people have less fat to insulate them.

Our body types evolved for different purposes, giving us totally different strengths and weaknesses:

  • Ectomorphs burn calories to keep them lean, light, and cool. Cardio tends to come naturally to us.
  • Endomorphs conserve calories to stay chubby, insulated, and warm. Strength training tends to go quite smoothly.

Even if you’re a classic ectomorph, though, it’s hardly a limitation. We can’t change our bone structure, but as you can see with our members, we can build muscle on top of it.

Being hardgainers doesn’t mean there’s anything wrong with us. We’ve just got genetics that are helpful in slightly different circumstances. For instance, we’re good at keeping cool while running long distances in the hot sun.

Skinny Guys Often Have 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. (I made this issue worse by trying to bulk while intermittent fasting.)

Even when I experimented with dirty bulking, getting more of my calories from sweets, treats, and grease, I still had a hard time gaining weight. It just seemed like my body was determined to resist weight gain no matter what I stuffed into it.

Illustration of the stomach size variation between skinny and overweight people.

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 second 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 a third 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 of 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. However, there are a number of effective strategies we can use to eat more calories more easily, and there are a lot of great bulking foods.

To summarize, guys with thinner torsos often have smaller stomachs, especially if they aren’t used to eating large meals. However, as we bulk up, our stomachs will grow along with us.

Hardgainers Tend to 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 at all, let alone leanly.

Here’s a quick primer on how insulin works:

  • When your insulin levels are low, you get hungry.
  • When you eat, your insulin levels go up, and the insulin shuttles the nutrients to the more insulin sensitive areas (such as muscle and fat). Whether you gain more muscle or fat depends on a number of different things, such as your genetics, what kind of food you ate, if you’ve recently lifted weights, how fat you are, and how full or depleted your fat cells are.
  • As your insulin levels rise, you start to feel full, and so you stop eating.

The thing is, as soon as you’ve eaten enough food to maintain your body weight, your rising insulin levels cause you to feel full (if everything is working properly). And for a hardgainer, fullness is no joke. Because of how insulin sensitive we are, fullness is a very strong signal. It can be extremely unpleasant to continue eating, and so it can be very hard to gain weight.

This is rather different from the typical overweight person. Being overweight makes people less insulin sensitive, and so all of these signals are slow and blunted. 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 meekly that it’s easy to ignore. If the average person wants to gain weight, they can just do it. That’s why you’ll often hear overweight people telling skinny guys to “just eat more.” They assume that it’s as easy for us as it is for them.

To be clear, insulin is part of your body’s weight 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 of us ectomorphs are, then bulking up can dramatically improve our health, strength, and appearance. Being insulin sensitive can make that much harder. It can be extremely frustrating. I hated it.

However, as we alluded to earlier, insulin has another role. Insulin also affects what kind of weight we gain while bulking. This phenomenon is called nutrient partitioning, and it works like this:

  • If your fat cells are more insulin sensitive, you’ll gain more fat.
  • If your muscles are more insulin sensitive, you’ll gain more muscle.

Overweight people often run into a problem where their fat cells are more insulin sensitive than their muscle fibres, and so rising insulin levels can cause them to gain fat. Because of that, there are a number of different diet trends designed to limit insulin production ketogenic diets (where insulin is kept low by avoiding carbs) and intermittent fasting (where insulin is kept low during the fasting period).

However, as naturally skinny hardgainers, we don’t tend to have those problems, especially if we lift weights and get a proper night’s rest. If you’re following a good bulking program, your muscle fibres will be more insulin sensitive than your fat cells, and so as your insulin levels rise (mainly from eating protein and carbs), you’ll be shuttling more nutrients towards muscle growth, less towards fat storage.

That’s where a lot of skinny guys get confused. They see all of these overweight people trying to reduce their insulin to get rid of fat, not realizing that insulin is also responsible for muscle growth.

When we train for muscle growth (hypertrophy training), then the insulin sensitivity in our muscles rises way higher for up to around 72 hours (study). During this period, the extra calories we’re eating are more likely to be invested in muscle growth. We don’t want to limit our carbs, we want to be eating plenty of them. We don’t want to skip breakfast, we want to add in an extra meal. And in that extra meal, we want to include some protein and carbs.

Essentially, we want to stimulate muscle growth with our training, and then create a situation where we can be shuttling nutrients towards muscle growth all day long. (This is the approach that bodybuilders take, too, and some of the crazier ones even inject insulin.)

What’s neat is that just like gaining fat makes our fat cells more insulin sensitive, building muscle makes our muscles more insulin sensitive. So having good insulin sensitivity makes it easier to build muscle, and building muscle further improves our insulin sensitivity (study).

This is one of the reasons why skinny hardgainers can bulk so aggressively, building muscle so quickly and leanly. I’ve always tried to gain at least a pound per week while bulking, which can seem quite fast to the average person, and we often have members who bulk even more quickly than that:

Eating more calories with a small appetite, fast metabolism and small stomach

To summarize, one of the reasons that it’s hard to gain weight is because our appetite turns off once we’ve eaten enough to maintain our body weight. This happens because we’re insulin sensitive, and it’s a good thing. Not only is it healthy, but if we follow a good hypertrophy training program, having better insulin sensitivity helps us build muscle more quickly and leanly.

Hardgainers Do Indeed 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, and that can certainly happen. As we’ll cover later, sometimes being stressed or busy can turn off our appetites and make us forget to eat. For some hardgainers, 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. That also explains part of the mystery, and it has nothing to do with us underreporting our calorie intake.

The mystery is far more interesting than any of that, though. When researchers have conducted overfeeding studies to study fat gain, they realized that some of the participants weren’t gaining weight even though they were eating in a large calorie surplus.

What We Can Learn From Overfeeding Studies

In one study, the participants were overfed by a thousand 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 the researchers expected: if you overeat, you gain weight. And if you overeat without exercising, most of that weight gain is fat.

However, there were also a couple of participants who hardly gained any weight, with one guy gaining just 0.79 pounds. This was a puzzling result, so they came up with a name for these superhuman creatures: hardgainers. What was interesting is that the researchers had no idea where these extra calories were disappearing to. The calories were vanishing into thin air.

These hardgainer wizards remained a mystery until a group of researchers discovered that we burn extra calories through subconscious activity, such as fidgeting and adopting odd postures (study). While this may not sound like a big deal, the effect can be 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).

The Skinny on how to Eat More as an Ectomorph – Us hardgainers burn a lot more calories (way higher metabolism)

Depending on how much of your time you spend standing, that works out to burning an extra 600–950 calories each day, which explains how a thousand calories can disappear. And that’s not even the whole story. 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 by eating 13x his body weight (in pounds) in calories each day. If he weighs 150 pounds, that means eating about 2,000 calories per day. If he eats more than that, he may start gaining fat.

A hardgainer, on the other hand, might be able to eat 22x their body weight each day without gaining any fat. For someone who weighs 150 pounds, that’s 3,300 calories per day. That’s a big difference, especially when considering our higher insulin sensitivity and smaller stomachs.

However, note that hardgainers can maintain their 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. It’s not that our metabolisms are always running faster, it’s just that when we eat more calories, our furnaces kick into a higher gear.

To summarise, not only is it incredibly difficult to eat more calories, but even if we do, our metabolisms will often adapt to our higher calorie intakes, rendering our bulking attempts futile.

Is It Impossible for Hardgainers to Gain Weight?

It’s not impossible for a hardgainer to gain weight, it’s just harder, and it calls for a more deliberate approach. We just need a little finesse, especially because we aren’t simply trying to gain weight, we’re trying to build muscle

Because we have the specific goal of building muscle, we don’t want to do a general weight training program. There are a number of different ways of lifting weights, ranging from cardio-oriented programs like CrossFit to strength-oriented programs like Starting Strength and StrongLifts 5×5. These are good programs in many ways, but they aren’t designed to stimulate a maximal amount of muscle growth. The type of training specifically designed for gaining muscle size is called hypertrophy training.

Illustration of a skinny guy becoming muscular from doing biceps curls.

Being a hardgainer makes us resistant to fat gain but not muscle gain. So when we stimulate muscle growth by following a good hypertrophy training program, then instead of revving up our metabolisms to prevent fat gain, we’ll keep some of those extra calories to invest in muscle growth.

Being a hardgainer causes us to burn off unneeded calories. But if we’re stimulating a ton of muscle growth with our workout routines, then the extra calories we’re eating are no longer unneeded. After all, calories that need to be invested in building bigger biceps aren’t extra calories.

It gets better, too. If our training makes our bodies desperate enough to build muscle, then our appetite can rise, too. After all, our appetite is designed to prevent haphazard weight gain, not to prevent necessary adaptations that are deemed critical to our wellbeing. If we signal to our bodies that building muscle is a high priority, our appetites will often rise accordingly.

Now, this doesn’t last forever. You probably won’t have a big appetite for months on end. Your body will try to find a new set point. By the time you gain five, ten, or twenty pounds, it will probably want a break from the overeating. But a good hypertrophy training program can raise your appetite, at least for a little while.

Finally, as a word of caution, 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, especially if we’re following a good hypertrophy program and eating enough protein, but it’s often wise for skinny guys to cap their weight gain at around a pound per week.

To summarize, can help us build muscle out of the extra food we’re eating before our metabolisms torch all the extra calories. Plus, a good weight training program will often cause our appetites to rise!

Some People Lose Their Appetites When Stressed

Our small stomachs, insulin sensitivity and fast metabolisms make it hard to eat enough on a good day. But 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, hardgainers 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. As a result, it’s common for people to turn to food when they’re tired or stressed, 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.

For us skiny hardgainers, though, things are a little different. First of all, because we’re so insulin sensitive (as explained above), our bony hearts are mendable with relatively small portions of ice cream. Second of all, ectomorphs don’t drown their sorrows in ice cream to begin with (study, study). When we get stressed, heartbroken, or tired, we often lose our appetites entirely. We’ll often entirely forget to eat.

There are a couple of reasons why hardgainers lose weight during hard times:

  • A lower hedonistic response to food: different people get different amounts of pleasure from the food they eat. Most of us hardgainers have a lower hedonistic response to food, i.e., we aren’t as likely to seek out food as a source of pleasure. And so in tough times, we tend to find ourselves losing weight. For example, if you get in a fight with your gal, she might storm off and raid the fridge, whereas you forget that the fridge even exists.
  • Periods of high stress always cause a loss of appetite: when our stress levels are exceptionally high, it makes sense to prioritize short-term needs over longer-term ones. As the Stanford researcher Robert Sapolsky explains in Why Zebras Don’t Get Ulcers, if we’re being chased by lions, it’s not a good time to eat or digest food. Not only does our appetite shut down, but so does our digestive system. In some cases, we even get diarrhea. And digestion problems can make it much harder to bulk up.

Fortunately, there are a few things that we can do to reduce stress. Some people turn to prayer or meditation, others turn to stress-reduction supplements like ashwagandha or rhodiola rosea. All of that can work, and if you’re having trouble with stress, it might be worth experimenting with. However, there are three other methods that are quite effective for reducing stress while building muscle:

  • Hypertrophy training lowers stress: a number of studies have found that weight training reduces stress, but what’s interesting is that training in moderate rep ranges (of around twelve reps per set) seems to have the biggest stress-reduction effect. This is a rep range that’s more commonly used in hypertrophy training, which is a fortunate coincidence (systematic review).
  • Being active lowers stress: the next way to lower stress is to exercise regularly (study). This could be cardio or weight training, but if stress is bothering you, we’d recommend doing a bit of both. What often works well for bulking is to lift weights 2–4 times per week and then to do relaxing cardio (such as going on 30-minute walks outside) another 2–3 times per week. Even better if you go on a morning walk and get a bit of sunshine. This not only reduces stress, but it also helps us recover from our more strenuous weight training workouts.
  • Improving sleep lowers stress: the final way to reduce stress while building muscle is to improve our sleep. If we don’t get enough good sleep, our levels of the stress hormone cortisol are elevated the next morning, which can lead to higher stress levels throughout the day (study). And if we can improve our sleep, not only will we feel less stressed, but we’ll also build muscle around 30% faster, we’ll gain less fat, have more willpower, and our training performance will rise. For more on this, we have an article on how to improve sleep.

What’s nice about all of these stress-reduction techniques is that they synergize. Lifting weights reduces stress, which makes it easier to get a good night’s rest. Getting a good night’s rest gives us more energy to work out, and it also speeds up muscle growth, improving our training. And as we become stronger and fitter our sleep improves even more. The benefits compound.

The same is true with being active. Going on a walk outside doesn’t just lower stress, it also stimulates the production of melatonin, which makes it easier to fall and stay asleep. As a result, any small improvement in your lifestyle has the potential to grow over time as the benefits continue to compound.

To summarize, it’s important to get regular exercise, manage our stress, and get enough good sleep while bulking. Not only will it help increase our appetites and improve our digestion, it will also help us build muscle more quickly and leanly.

Lifting Weights Can Suppress Our Appetites

It isn’t just emotional stress that can suppress our appetites. Physical stress can also make us less hungry, including lifting weights. Now, as we covered above, hypertrophy training makes most guys ravenous, but that’s not always the case. In fact, I’ve often found that lifting weights has suppressed my appetite.

According to a study published in Physiology and Behavior, although lifting causes most people to eat more calories, it also makes some people eat fewer calories. Other studies found the same effect (study, study, study). For some people, lifting weights can suppress appetite.

Illustration of a man doing the barbell overhead press.

This is one reason why most guys naturally grow bigger and stronger when they start lifting weights. Their bodies automatically up-regulate their food intake when they start lifting weights to facilitate the muscle growth that they’ve stimulated. But it’s another reason why some guys mysteriously fail to gain weight.

Now, the type of exercise can play a role here, to. Generally, the more intense the exercise is, the more potential it has to suppress our appetites. Again, think of the zebra. If the zebra is highly stressed, such as when it’s being chased by a lion, then the last thing it will be thinking about is food. But if the activity is more moderate, then the stress response is lower, and appetite won’t be suppressed by as much, if at all.

Furthermore, even intense exercise only tends to suppress appetite for around an hour. Once stress levels fall off, our appetites tends to come back. with a vengeance. This would be a good time for a post-workout meal, but you may even want to get in ahead of it by having a mid-workout shake.

Back when I first started bulking up, I was having a lot of trouble eating enough calories after working out. By the time I’d waited for my stomach to settle after my afternoon snack, walked to the gym, worked out, walked home, and made dinner, a few hours had already gone by. My appetite would pick up an hour or two after lifting, yes, but by then I was already behind on my calories. And my stomach was so small that I just couldn’t catch up. If I tried, I’d feel sick and get acid reflux.

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

So what I’d do is mix some carbs and protein together into a workout shake and sip on it while working out. Not only will the protein and simple carbs boost workout performance and make our muscle gains leaner, but it also makes it far easier to eat enough calories to gain weight. If you’re interested, here’s our workout shake recipe. (Keep in mind that digestion can be impaired when training, so be careful about eating foods that are hard to digest right before or during your workouts. The shake is simple and low in fibre for a reason. It’s designed to be quick and easy to digest.)

Finally, it’s not just weight training that can suppress our appetites. If you do intense cardio exercise, that can also delay your desire to eat as well as interfere with your digestion. That isn’t necessarily bad, but it’s something. to be mindful of, and it’s one of the reasons why we generally recommend going on a brisk walk outside as a good default form of cardio while bulking.

To summarize, it’s normal for strenuous exercise to suppress our appetites and interfere with digestion. Our appetites usually spring back an hour or so later, but that may not be soon enough, so you may want to sip on a workout shake either while lifting or chug it immediately afterwards.

How Hard is it to Maintain the Weight We Gain?

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 forcing myself to eat more, my muscles would shrivel up and I’d be skinny again. A lot of our members have this same fear. No hardgainer wants to spend the rest of his life struggling to eat more calories.

Luckily I was dead wrong. A pound of muscle only burns six calories per day (studystudystudy), so gaining 20 pounds of muscle will only burn 120 extra calories per day. That’s barely a 5% increase in our metabolisms. It’s a small glass of milk or a cookie for dessert.

Building muscle requires consuming a lot of extra calories (among other things), but maintaining muscle does not. That makes sense intuitively, too, if you think about it. Building muscle requires extra materials. The muscle needs to be built out of something. But once we stop bulking, there’s no longer any need for surplus calories and protein. All we need to do is maintain what we’ve built, which is much easier.

For instance, when we stop actively building muscle, we can cut our protein intake in half, meaning that we won’t ever really need to think about it again. We can also trim at least 500 calories out of our diets, and often quite a bit more.

Plus, to make things even easier, there are a number of adaptions taking place under the hood as we bulk up:

  • As we gain weight, our skinny stomachs grow bigger, making it easier and more enjoyable to eat bigger meals.
  • As we get used to eating more food, our digestive systems get better at digesting all of that food, making us feel better when digesting bigger or more frequent meals.
  • As we build muscle, that extra lean mass raises our insulin sensitivity even higher, making it even easier to maintain low body-fat percentages.
Illustration of a man flexing flaming biceps.

Moreover, many of the changes in our muscle fibres are totally permanent. The glycogen we store in our muscles can fluctuate depending on how many calories and carbs we eat, causing us to deflate and inflate a little bit, but the extra nuclei we add to our muscle fibres will stay there for the rest of our lives—even during periods of starvation.

If you want to learn more about maintaining your weight after bulking. here’s our article about changing your set point. But the point is, once we build muscle, it becomes quite easy to stay muscular. You’ll find that you’re just “naturally” stronger and leaner.

To summarize, it’s common for skinny guys to worry about maintaining their weight after they bulk up, but it’s rarely an issue. Maintaining a higher weight doesn’t require a calorie surplus, muscle doesn’t burn many calories, and our stomachs and appetites grow along with us. Maintaining a higher weight is often as easy as maintaining a lower one. It’s only the bulking that’s hard.


Trying to eat enough to gain weight is a lot harder for ectomorphs than most people realize. Not only is eating more incredibly difficult, but our metabolisms can readily adapt to higher calorie intakes.

  • A hardgainer’s stomach can be up to six times smaller than an obese person’s. Not only does that make it harder to eat more calories, but if we aren’t careful, force-feeding ourselves can also lead to issues such as lethargy and acid reflux.
  • Even if a hardgainer succeeds at getting into a calorie surplus, their metabolism can burn up to 1,300 extra calories per day, making that surplus disappear into thin (albeit hot) air.
  • When the average person gets stressed, they eat more food and they gain weight. However, when naturally skinny people get stressed, we often lose our appetites and lose weight.

It’s not as simple as just eating more. Thinking that “just eat more” is a good muscle-building strategy is like thinking the ultimate fat-loss secret is “just eat less.” It’s not that the advice is scientifically inaccurate, it’s just that it’s not helpful. If you told that to a fat person, he’d probably eat you, and rightfully so.

Illustration of a skinny hardgainer building muscle and becoming muscular (before/after).

On the other hand, hardgainers have a number of genetic advantages. Not only do we need to worry less about chronic health problems like inflammation, obesity, and diabetes, but we can also build muscle more quickly and leanly than other body types. And once we’ve succeeded at building muscle, it’s often easier for us to maintain an attractively low body-fat percentage year-round.

To build muscle, it pays to be deliberate about it. Instead of merely exercising or strength training, we should lift in the way that’s specifically designed to stimulate muscle growth: hypertrophy training. Instead of simply eating a generally healthy diet, we should eat in a way that’s designed to help us gain weight: a bulking diet. And to improve our digestion, increase our muscle growth, and ward off fat gains, it can help to manage our stress and improve our sleep.

Before and after photo of a skinny guy gaining muscle in one year

If you want to a muscle-building program designed for skinny hardgainers by skinny hardgainers, then I think you’d love our Bony to Beastly Program. It includes a full bulking guide outlining how to eat and train for muscle growth, a 5-month hypertrophy training routine, a recipe book, membership in our coaching community, and absolutely everything else you need to know to bulk up.

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.