Illustration of a naturally skinny guy building bigger abs.

The Skinny Guy’s Guide to Building Bigger Abs

Why do some skinny guys with a low body-fat percentage not have visible abs? After all, for the average guy, getting abs simply requires getting lean. But what if you’re already lean and you still don’t have abs?

If you try to search for information about how to get abs, there are two types of advice that you’ll probably come across, neither of which apply to skinny guys:

  1. Abs are built in the kitchen, not the gym. Yes, most men get abs by dieting down to a lower body-fat percentage. That’s because most men are overweight, and most overweight men already have large ab muscles. After all, when someone gains weight, at least 33% of that weight is going to be muscle. Plus, the heavier someone is, the bigger their ab muscles will need to grow in order to support that extra weight. Overweight guys already have big abs. Skinny guys do not.
  2. Abs are built with high-rep ab routines—crunches, sit-ups, and so on. The most popular ab routines are high-rep circuits that are brutally painful but aren’t effective at stimulating muscle growth. Doing high-rep crunches to build bigger abs is like running a marathon to build bigger legs. High-rep circuits are designed to improve endurance and blood flow, not to stimulate muscle growth. Yes, you’ll see guys with great abs doing these routines. However, that’s not how they built their abs, it’s just something they do because they like their abs.

Neither of these pieces of advice work for skinny guys. After all, our problem is that our abs are too small. We need to build bigger ab muscles.

We need a bulking routine for our abs.

Before and after illustration of a skinny hardgainer ectomorph becoming muscular.

Why Do Some Skinny Guys Not Have Abs?

Some skinny guys don’t have visible abs. If you’ve heard that all it takes to have abs is to cut down to a lower body-fat percentage, that can be confusing.

In a way, abs are built in the kitchen. The average person overeats, causing them to gain weight. As they gain more weight, their abs need to grow stronger to support their heavier body. You could say, then, that abs are built in the kitchen. But it’s not dieting down to a low body-fat percentage that builds bigger abs, it’s becoming overweight that builds bigger abs.

However, as you can imagine, an overweight person’s abs are going to be hidden underneath a thick layer of fat. To reveal those big abs, then, they simply need to diet down to a lower body-fat percentage. Once they drop under around 12% body fat, boom: visible abs.

For skinny guys, things are a little different. We aren’t carrying around a bunch of heavy fat. We aren’t even carrying around a bunch of heavy muscle. Our abs don’t need to grow all that big in order to support our lighter bodies. Unfortunately, that means that sometimes even at low body-fat percentages, we still won’t have abs. It’s not because we aren’t lean enough; it’s because our abs are as skinny as we are.

If we want visible abs, we need to build them with hypertrophy training and bulking diets, just like we build the rest of our muscles.

GK is skinny but doesn't have abs.
GK was skinny but still didn’t have abs. He had to bulk them up.

For example, in GK’s before photo, he’s more than lean enough to have abs; they just aren’t big enough to be visible. Although I suppose you could say that his abs were built by eating everything in the kitchen, it’s probably more accurate to say that they were built by lifting weights.

We’ll start by going over your ab anatomy, and then we’ll talk about how to train your abs for muscle size.

The Skinny on Ab Anatomy

If you ask someone who’s into strength training how they got their abs, they’ll probably tell you that they built them with compound lifts. There’s some truth to that, sure.

Most compound lifts train our transverse abdominis abs, which act like a corset, cinching our waists in tight. They don’t train our rectus abdominis abs, which is what gives us a six-pack. So compound lifts do indeed train our ab muscles, just not the ab muscles that you can see.

Before we talk about how to build your six-pack abs (rectus abdominis), let’s quickly talk about the muscles that are underneath those abs—the transverse abdominis muscles.

Illustration of the anatomy of the transverse abdominis muscles.
The transverse abdominis muscles act like a lifting belt, keeping our cores stable.

When you brace your core, these are the ab muscles that you’re flexing. As you can imagine, they’re incredibly important when lifting weights. After all, we can’t even do biceps curls if our cores have the consistency of overcooked noodles. As skinny guys, these muscles are even more important. Our cores are thinner, and our spines need all of the support we can give them. However, these ab muscles are deep. You can’t see them. 

This is important because these are the ab muscles that are trained with squats, deadlifts, overhead presses, rows, and most other compound lifts. If you’re trying to bulk up your abs so that you can see them, these compound lifts won’t help.

When most people say abs, they’re usually talking about the rectus abdominis, which are situated on top of your transverse abdominis. Your rectus abdominis is made up of a series of muscle bellies and tendons. The bits that bulge out are the bellies; the canyons between those bulges are the tendons. This gives your abs their unique washboard shape:

Ectomorph Ab Anatomy (How to Build Bigger Abs as a Skinny Guy)

These ab muscles can flex, just like any muscle can, allowing us to move our core like an accordion. Our 6-pack abs allow us to crunch forwards, and our obliques allow us to twist around. These muscles can also help us resist movement, keeping our ribs and hips in place when lifting weights. They aren’t very active during squats and deadlifts, but they do help keep our core stable during a couple of compound lifts.

Two compound lifts are great for training the rectus abdominis: the chin-up and the push-up. If you do a good job of keeping your core locked down while doing chin-ups and push-ups, your abs will be firing to keep your ribcage and hips in the proper position.

If your bulking routine has lots of push-ups and chin-ups, you might do a good job of stimulating your ab muscles. However, if you’re a naturally skinny guy and you’re trying to build bigger abs, that probably won’t be enough. After all, those exercises rely on our body weight to provide resistance, and our body weight doesn’t tend to be very heavy.

As a skinny guy, you’ll probably want to directly target your abs. That’s going to make your abs look better, and it’s also going to give your core more stability, improving your posture and allowing you to lift more safely.

How to Build Upper and Lower Abs

As you build bigger abs, you’ll soon notice that they have their own distinct shape. You can make your ab muscles bigger with good training, but you can’t do anything to affect their symmetry or alter the number of tendons that you have. Some have an 8-pack, and others have a 6-pack. Some have a wide pack, others have a thin pack.

Bony to Beastly Genetics 6-pack or 8-pack abs

However, in a controversial new study, research has proven what belly dancers have known for thousands of years: with enough coordination, you can target your upper and lower abs (study).

Most guys can’t see their lower abs. So after learning this, most guys will assume they have smaller lower abs, and they’ll start looking for exercises that target their lower abs, such as reverse crunches.

Although it’s possible that your lower ab muscles are disproportionately small, keep in mind that men store more body fat on their lower stomachs than their upper stomachs. Lower abs tend to be murky unless you are very lean—under 10% body fat.

Illustration of a man with smaller lower abs because of a higher body-fat percentage.

Another reason you can’t see your lower abs might be that you don’t have any lower abs. If you take a look at Arnold Schwarzenegger, for example, you can see that underneath his belly button, he doesn’t have any tendons running across his abs. No matter how big Schwarzenegger builds his lower abs, he’ll never have any ab definition on his lower stomach. He simply doesn’t have lower abs.

arnold schwarzenegger lower abs

The good news is that having lower abs doesn’t really matter. If your abs are strong and lean, it doesn’t really matter whether they’re symmetrical or whether you have great lower-ab genetics.

Keep in mind that having great abs is just a proxy for being lean and muscular overall. Sometimes we get caught up in these minor aesthetic details. We get caught up trying to build the perfect shoulder-to-waist ratio, forgetting that it doesn’t matter how long our collarbones are; it just matters how big and strong our shoulders are. The same is true with our abs. What matters is being lean and strong.

If you have big ab muscles that are well-defined, they’ll look awesome. Arnold Schwarzenegger is proof of that, of course, having built one of the most famous physiques of all time despite having no lower abs whatsoever.

Every set of abs will look different. All abs look good.

How Lean Do You Need to Be to Have Abs?

Not all skinny guys have a low body-fat percentage. Many do, but it’s fairly common for skinny guys to be between 15–20% body fat. If you’re between 15–20% body fat, it’s fairly common to have thin arms and a thin face but a softer stomach.

If you aren’t lean enough to have visible abs, building up bigger ab muscles will just push the fat out further:

Ab Bulking at 15

For a flat stomach, you’ll want to be at around 15% body fat. That’s enough to make you attractive to most women, but it’s not enough to have clear abs.

To have clear abs you’ll usually need to be under 12% body fat. If you’re curious about how lean you are, here’s how to visually estimate your body-fat percentage by looking at your stomach.

But if you want to see how lean you need to be to have abs, here’s me at 10.8% body fat as measured by DEXA. You can see that my abs are just barely coming in. If I were just a couple of body-fat percentage points higher, they’d be completely covered:

Bony to Beastly Shane Duquette Body Fat Percentage DEXA Scan

As you can see, my ab muscles are quite small, even though I’ve got a fair bit of muscle overall. This is because I gained 55 pounds of muscle without any direct ab training. The most stimulation my abs got was from push-ups and chin-ups. Because I never directly trained my abs, they never grew much bigger as I bulked up.

Anyway, let’s say you’re closer to 20% body fat. That’s not an overly high body-fat percentage. That’s still within the healthy range. However, your abs will be completely covered. At that point, regardless of whether your ab muscles are big or not, your best bet is to cut.

As you lose fat, you can carve out your abs. They might not be big yet, but once they’re hard, you’ve got something to work with:

Bony to Beastly Cutting Body Fat Percentage

While cutting down to a lower body-fat percentage, you’ll want to be following a good lifting program. If you’re already somewhat muscular (as I was) you can expect to maintain your muscle mass and strength. But if you’ve only just started working out, you should be able to build some muscle while losing fat.

(We’ve got a free guide here on what to do if you’re skinny-fat.)

So whether you’re under 15% or not, if you eventually want abs, you should be doing ab workouts along with your hypertrophy program. This means that whether you’re lean enough for abs or not, you need to be lifting.

How Can a Skinny Guy Build Bigger Abs?

We’re going to teach you the best exercises for building bigger ab muscles, but keep in mind that we need to get your hips positioned properly in order to get your ab muscles firing properly.

That way your abs won’t be hanging loose as you stroll around town, your gut won’t be jutting out even though you’re at 9% body fat, and eating a big meal won’t make you look quite as pregnant.

ecto-belly vs good posture with strong abs

If you want to see what this looks like in real life, check this out:

Europa's Bony to Beastly Ectomorph Transformation

This should also help fix the “lazy stomach” that some guys get when they aren’t intentionally flexing their ab muscles. Some degree of this is okay, but it’s best if your abs have the strength, positioning and endurance to always have a little bit of tension in them.

Here are two pictures that one of our members took just seconds apart. In the left photo, even with a low body-fat percentage, his ab positioning is preventing him from having abs. When your stomach is stretched like that it prevents the abdominal muscles from contracting properly, which can ruin a skinny guy’s ab definition:

lazy stomach vs good posture with strong abs

Fortunately, stronger ab muscles are better at holding your hips and ribs together. This means that building up bigger abs will improve your posture, and improving your posture will help you build bigger abs. These goals work additively with one another. By focusing on both simultaneously you’ll get the quickest (and best) results.

Ab Workout for Skinny Guys

There are a few ab exercises that are particularly effective for getting your hips into a proper position and building bigger ab muscles. Here are six different exercises that will bulk up your abs in different ways, improve your posture, and help you bulk up the rest of your body as you do it.

The plank: The plank is great for teaching your abs how to become comfortable maintaining good posture under load. It’s an isometric exercise, meaning that you’re stimulating your ab muscles by resisting movement.

Front Plank Demonstration

The farmer carry: In this exercise, we’re teaching your abs how to maintain a plank position while walking around with heavy things. This isn’t really an exercise for your abs, per se, but it’s great for your obliques, which are just as important for improving the appearance (and function) of your core.

Farmer Carry Demonstration

The Sit-Up: Crunches involve repeatedly bending your spine under load, and while that isn’t always harmful, the most respected spinal health expert in the world, Dr. Stuart McGill, advises against them. Instead, he recommends variations where the spine remains in a more neutral position.

These spine-conscious variations will also ingrain better lifting habits, as you’ll learn how to keep your abs on lockdown during compound lifts. This makes them a better ab exercise for a skinny guy who’s trying to build bigger muscles overall.

Dumbbell Pullovers: In this ab exercise, you’re moving in the shoulder joint while your abs fight to keep your ribs down. The bigger and stronger your back and chest get, the bigger and stronger your abs will become.

Pullover Demonstration

Goblet Squats. In this exercise, you’re moving in the hips while your entire core is lit up. The bigger and stronger your entire body becomes, the bigger and stronger your core will become. Again, it’s not specifically an ab exercise, but it’s fantastic for your obliques and spinal erectors, which will make your core look quite a bit better (and much stronger).

Goblet Squat Demonstration

Reverse Crunches: The reverse crunch works your abs through a fairly large range of motion, making it great for bulking your ab muscles up. What makes it even better is that it trains the lower abs a little harder than the upper abs, which balances out the other exercises, which focus mainly on the upper abs. This ab exercise is also good for your posture, which is an important part of having visible abs.

Reverse Crunch Demonstration

If you make a habit of doing one or two of these exercises every workout, your abs will grow quickly. When they become easy, just switch to more difficult variations, such as hanging leg raises and ab-wheel roll-outs.

Key Takeaways

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

It’s common for naturally skinny guys to have smaller ab muscles, meaning that they don’t show through very well, even at lower body-fat percentages. Fortunately, just like with the rest of our muscles, we can bulk up our abs.

As a skinny guy, building bigger ab muscles comes down to three things:

  1. Bulk up your abs just like any other muscle group. The same principles of hypertrophy that apply to your other muscles also apply to your abs. Train them heavy enough and often enough to stimulate muscle growth.
  2. Cut down to under 12% body fat if you want good ab definition.
  3. Strengthen your posture so that your abs will activate and flex naturally.

Also, remember that you don’t need abs. You’re perfectly healthy at 18% body fat and perfectly attractive to women at 15% body fat. Abs are a bonus. So there’s no need to stress if you lose sight of your lower abs when bulking. You’ll get them back. And when you do, they’ll probably be bigger than when you last saw them.

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

If you want more muscle-building information, we have a free bulking newsletter for skinny guys. If you want a full bulking program, including a 5-month workout routine, diet guide, recipe book, and online coaching, check out our Bony to Beastly Bulking Program. Or, if you want an intermediate bulking routine, check out our Outlift Intermediate Bulking 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.