Does ab training increase your waist size?

Does anyone else find it a little weird that we lift weights to make our muscles bigger and stronger, but we do ab exercises hoping to make our waist look smaller?

How do ab workouts make your stomach smaller if exercising these muscles makes them bigger?

It’s no wonder that so many of us are confused and not seeing the results we’re looking for in the gym.

Push, pop, and pump

When it comes to our muscles, there are basically three qualities they can have: strength, power, and endurance.

Without falling too far down the scientific rabbit hole here, we’re going to define strength as the amount of force a muscle can produce, power as how quickly that force can be produced, and endurance as how long a muscle can continue to create that force without stopping.

Bigger is not always better

Many of our muscles have a distinctive role. For example, the muscles in our arms and legs are mostly used for movement, while our core muscles are used primarily for stability.

So even though having big muscles in our arms and legs can be an advantage, the same is not necessarily true for our stabilizing core muscles which consist of our abs, obliques, transversus abdominis, and lower back muscles.

In other words, we need strong core muscles, but we don’t always want big core muscles. This is also the reason why we shouldn’t be training our core muscles the same way we train the muscles in our arms and legs. 

In fact, we could say that the primary job of our core muscles is to resist movement rather than create it. This anti-rotation (flexion/extension) ability is how our core muscles help protect our spine and prevent injuries.

Now having said that, there is one set of ab muscles called the rectus abdominis that many of us want to make bigger in order to get those elusive six-pack abs. We’ll talk about how exactly we can do this in a moment, but first, we need to understand why doing side bends and similar exercises may actually make our waist look bigger. 

The hourglass vs. the tree trunk

I frequently see people in the gym doing side bends or ab twists while holding a dumbbell in an effort to burn off the fat around their abs, which unfortunately isn’t very effective. 

The problem is that even though they may not be reducing the fat around their waist, they are building up their oblique muscles, which can lead to a thickening of the waist and a blockier “tree trunk” appearance versus the desired “hourglass” shape where the waist is smaller than the hips.

Unlike your six-pack ab muscles, the rest of your core muscles, including your obliques (aka side abs), lower back muscles, internal ab muscles such as the transversus abdominis are primarily stabilization and support muscles, which means that we want them strong, but not necessarily big.

The myth of spot reduction 

Okay, before we move on, let’s take a moment to talk about the fat elephant in the room.

Here’s the thing. . . No matter how many crunches and planks we do, we are never going to be able to see the results we want until we remove the blanket of fat covering up those muscles underneath.

Research has repeatedly shown that spot reduction of fat is a fantasy with a few possible exceptions. This means we can’t lose fat in a certain area of our body by exercising that part of our body.

When we exercise, fatty acids are released into our bloodstream and then travel throughout our body. In other words, fat doesn’t just get released from our abs when we do ab crunches.

 And even if this was the way things worked, because these fatty acids are flowing around freely in our bloodstream, there’s nothing to stop them from being re-deposited around our waist later on.

The most effective ab exercise is done in the kitchen

Honestly, I think most people would be shocked by how much muscle they already have. 

The problem is that most of us simply can’t see them because even the thinnest layer of fat will smooth out the cuts that divide your muscles and make you look ripped.

This is why even though bodybuilders may not have the biggest or strongest muscles, it often appears they do because they have the least amount of fat covering them. 

For example, the man on the left is the late great Franco Columbo, who was 5’5” and weighed about 187 lbs in his prime. The man on the right is Eddie Hall, who is one of the strongest men in the world. He is 6’3” and weighs over 360 pounds.

Now even though Eddie Hall is stronger and probably has bigger muscles than virtually any bodybuilder alive, when you look at these pictures you might think otherwise because his muscles are hidden beneath a layer of fat.

In other words, you can have the biggest ab muscles in the world, but if they are covered up by a blanket of fat, no one is ever going to see them.

Building bigger ab muscles

When most of us think of “ab muscles” what we are really thinking about is a particular ab muscle called the rectus abdominis.

This is the muscle that gives us the coveted washboard or turtle shell abs, and its job is to curl our hips and shoulders closer together. 

Any exercise that simulates this type of movement is working the rectus abdominis muscle. This generally means crunches, reverse crunches, cable crunches, and machine crunches (noticing a pattern here?)

That’s only part of the equation, however, because if you want that muscle to grow (versus simply getting stronger) you’ll need to exercise it with higher reps (8-15) and multiple sets close to failure

It’s this last part (close to failure) that a lot of people forget. As with most bodyweight exercises, you will eventually reach a point where just doing more crunches is not better. 

I have known people who could do hundreds of crunches in a workout and still not see the results they are looking for because they were no longer challenging their abs to grow larger, they were simply increasing their muscular endurance.

They have the volume (lots of reps) but are missing the other half of the equation, which is gradually ramping up the intensity by continually adding more weight (resistance) to the exercise.

Higher Volume + Progressive Intensity = Muscle Growth

This means that at some point, you will need to add some external weight to your ab crunch exercises. This could be something as simple as holding a weight plate to your chest during crunches or adding more weight to your cable or machine weighted crunches.

Building stronger ab muscles

Unfortunately, a lot of people believe that what is good for one ab muscle (rectus abdominis) is good for all of our core muscles. 

This is why you see all of these people at the gym cranking out set after set of side bends, abdominal twists, and back extensions. 

The problem with this (as we’ve already talked about) is that we don’t really want these other abdominal and back muscles to grow. We just want them to be stronger to better support our core and spine.

The forgotten strength builder

So what we need is an exercise technique that is able to build a muscle’s strength and endurance, without increasing the size of that muscle. This would be ideal for your remaining core muscles, including your obliques, internal ab, and lower back muscles.

Muscular holds such as planks and anti-rotational movements like suitcase carries or one arm presses are ideal because they allow us to build strength and endurance in these vital core muscles without the unwanted bulk.

These exercises are ideal because they reflect our core muscles’ primary purpose, which is to resist movement. 

Core anti-rotational movements

So although it’s okay to keep doing your abdominal crunches, you also need to train the rest of your core muscles for strength and endurance rather than size. We do this by using specific exercises such as muscular holds, suitcase carries, and unilateral pressing movements.

Here are some of the best exercises you can do to strengthen your core:

Keep in mind that if you do these core exercises before your workout, you may increase your risk of injury due to exhaustion of your core muscle. This is why it is recommended that all of these exercises be done either at the end of a weight training session or on an alternate day. 

The bottom line…

Many of our muscles have a distinctive role. For example, the muscles in our arms and legs are mostly used for movement, while our core muscles are used primarily for stability.

So even though having big strong muscles in our arms and legs is often an advantage, the same is not necessarily true for our stabilizing core muscles which consist of our abs, obliques, transversus abdominis, and lower back muscles.

There is one set of ab muscles called the rectus abdominis that we may want to make bigger to get those elusive six-pack abs. We can build up this muscle with a variety of crunches using higher reps (8-15) and multiple sets close to failure

Keep in mind, however, that no matter how much muscle you build, you must remove the layer of fat covering those muscles in order to see results.

The rest of our core muscles are primarily designed to resist movement rather than create it. This anti-rotation (flexion/extension) ability is how our core muscles help protect our spine, stabilize our movements, and prevent injuries.

For these specific core muscles, you’ll want to keep the weight moderate and the reps in the 10-15 range in order to focus on building strength and muscular endurance. 

Muscular holds like planks and anti-rotation movements like suitcase carries, and one arm presses are ideal exercises because they will increase the strength and muscular endurance of these vital core muscles without increasing their overall size.

What do you think?

Have you had (or not had) success when it comes to getting the type of abs you’ve been wanting? What type of exercises or advice have you found to be the most and least helpful? What would you recommend to someone who has become frustrated and discouraged? If you would please take a moment to share your story and experiences with us in the comment section below.


Vispute, S.S., et al., The effect of abdominal exercise on abdominal fat. J Strength Cond Res, 2011. 25(9): p. 2559-64. 

Katch, F.I., et al., Effects of Sit up Exercise Training on Adipose Cell Size and Adiposity. Research Quarterly for Exercise and Sport, 1984. 55(3): p. 242-247. 

Gwinup, G., et al., Thickness of subcutaneous fat and activity of underlying muscles. Annals of Internal Medicine, 1971. 74(3): p. 408-411.

Kostek, M.A., et al., Subcutaneous fat alterations resulting from an upper-body resistance training program. Med Sci Sports Exerc, 2007. 39(7): p. 1177-85.

Ramirez-Campillo, R., et al., Regional fat changes induced by localized muscle endurance resistance training. J Strength Cond Res, 2013. 27(8): p. 2219-24. 

Scotto di Palumbo, A., et al., Effect of combined resistance and endurance exercise training on regional fat loss. J Sports Med Phys Fitness, 2017. 57(6): p. 794-801. 

Drew Kimble CSCS*D, CPT
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