Most folks at various points in their own fitness journey are usually looking to gain muscle.
They want to get stronger and look more athletic overall. Makes sense.
You also hear about people wanting to lose fat, which... duh.
But I want to talk about a different goal that sounds kind of odd at first, but is actually much more common than you might think.
How do you lose muscle mass on purpose?
In very brief and simple terms, here's what you need to do to lose muscle mass and get skinny:
- Eat at a calorie deficit
- Do cardio
- Eat less protein
- Stop (or do less) strength training
Still, there's actually a lot of factors to consider and a ton of different variations on losing muscle, which we'll get into below.
(And be sure to check out my top recommended workout program for women who want a lean, toned physique)
Why would someone want to lose muscle mass?
I know, I know.
The idea runs so contrary to what many of us set out to do when we start training, but there are actually a ton of totally valid reasons for wanting to reduce your overall muscle mass, or to lose muscle in your legs or another specific body part.
- You've been packing on muscle for a while and want to slim down for aesthetics
- You want to decrease the size of a particular muscle group (say, your legs)
- You need to alter your body type for a specific sport or activity
Fitness YouTuber Omar Isuf recently talked about how muscle mass in his arms was actually getting in the way of his form while doing Olympic style weight lifting, so he decided to stop directly training his arms in order to lose size there. That'd be a sport-specific reasoning.
Or you might just decide you don't really like the bodybuilder look and want to go for more of an "underwear model" type physique. That's totally cool.
You might not really like the way your muscles are fitting into your clothes, so you may want to lose muscle in your legs so jeans fit better, for example.
There are a ton of reasons for wanting to lose muscle, and they're all completely valid.
So let's dive in to how to do it:
Step by step guide to losing muscle mass
There's really four things you need to do consistently to lose muscle mass:
1. Eat at a calorie deficit
This is the golden rule of losing any kind of weight and it holds true here. Calories In Calories Out (or CICO) is the tried and true method for shedding mass of any kind. And it goes like this:
Everyone has a set level of "maintenance calories," called Total Daily Energy Expenditure, based on his or her gender, age, weight, and activity level.
Basically, how many calories do you burn in a day just by existing?
If you eat roughly the same number of calories you expend in a day, you'll neither gain nor lose weight. You'll "maintain" your general body shape, size, and composition.
To gain weight (whether on purpose or just because you DGAF), you'll have to eat at a calorie surplus, or at least a couple of hundred calories over your maintenance level.
To lose weight, you'll want to eat a few hundred calories below maintenance. 500 or so fewer calories than your maintenance is a good and safe place to start.
You can calculate your own TDEE by using an online calculator like this one. Eat less than that to lose body mass.
2. Do cardio
This one is (maybe) optional, but can be an important tool in losing any kind of weight, even muscle.
Long and/or intense cardio workouts can burn a lot of calories, and will help keep you in the calorie deficit described above. You'll burn somewhere around 100 calories per mile running and roughly half that walking.
There's also some evidence that fasted-cardio, ie working out when you first wake up and you have nothing in your stomach and no food energy to burn, can accelerate muscle loss.
3. Eat less protein
You probably already know that eating a lot of protein is a crucial part of gaining muscle.
There's a lot of fancy reasons for this involving amino acids and such, but one of the biggest things to know is that protein contains nitrogen, and when our bodies are in a positive nitrogen balance, they become capable of growth.
This is important because some people will argue that a high protein diet (and therefore a high nitrogen level in your body) can allow for muscle growth even while eating at a calorie deficit.
For this reason, if you're looking to lose muscle mass, cut your protein intake.
But please be careful not to go too low: 0.36 grams per pound of bodyweight every day is the recommended amount, far lower than the amount usually recommended for building new muscle. That should be plenty low enough.
4. Stop (or do less) strength training
This is an obvious one. If you want to lose muscle, stop training your muscles!
There are a lot of different factors that go into how long it will take for your muscles to shrink or atrophy after you stop training them, but be sure that it will happen if you're not giving them the stimulus they need to grow or maintain their size. (Somewhere between two and 12 weeks is normal)
If you want to lose muscle in your arms, stop doing arm work. If you want to lose muscle in your legs, stop doing leg work. It's that simple.
Another thing to look out for, especially if you want to lose muscle mass in your legs, is to avoid things that might "pump" them up. That includes lifting weights but also things like riding a stationary bike or elliptical.
Stick to running or jogging.
And that just about covers it!
How to lose fat without gaining muscle
This is an interesting related question and might come to mind for people who want to get lean but are afraid of packing on size from strength training.
Your best bet here is to do much of what's prescribed above:
- Eat at a calorie deficit
- Don't strength train
- Do cardio
If you stick to jogging and running, you won't build much muscle over your body. This kind of cardio mostly serves to keep you in a calorie deficit so you drop fat and muscle simultaneously.
How to lose muscle without losing strength
Well this is an interesting one.
But it makes sense if you think about it. Someone could want to lose muscle mass for any of the reasons listed above — say, they want to be more nimble on the soccer field.
That doesn't mean they want to be weaker overall.
The best strategy for losing muscle mass without losing strength will be to do all of the above (eat at a calorie deficit, lower protein intake, and do cardio) BUT continue to strength train in the gym.
You'll just alter your training a bit. See, there is a such thing as 'neural training,' and it's what happens when you work with extremely heavy weight at very low rep ranges, like 1-3 reps per set.
Very little hypertrophy (muscle damage) happens in rep ranges that low, so lots of muscle regrowth is unlikely. But the heavy loads are extremely taxing on your central nervous system and force it to learn to recruit muscle much more efficiently to accommodate the lift.
It's possible to maintain strength or even get stronger by mostly training your nervous system: lifting very heavy for very low reps.
(Though without the right nutrition for recovery, it's likely you'll lose some strength while losing muscle mass. That's life.)
Don't forget to check out the absolute most-effective workout for women who want a lean, toned bod!