For our inaugural “Ask an Iron Mama” column, we received a question from a reader who has been strength training and exercising but not losing weight and wonders why.
What a great question! Thank you, Rachel! I am sure a lot of people have been exercising but not losing weight. There’s more here to unpack than you might expect.
First of all, I’m thrilled that you understand the difference between muscle and fat and the role they play in weight and body composition. Many people don’t know about this, so let’s start there to make sure we’re all on the same page.
What I have found is that most people who want to lose WEIGHT actually want to lose FAT.
Unfortunately, most people don’t know how to do this properly and end up losing both fat AND muscle. But that’s almost never their actual goal, and it shouldn’t be. We need to vigorously protect our muscle mass, especially as we age.
There are two possible primary reasons why Rachel may be exercising but not losing weight.
The first possibility is that Rachel is successfully losing fat and gaining muscle, which is presumably her goal. If that’s the case, the scale may not move much at all. In fact, Rachel’s weight could theoretically even go UP with enough progress in the gym.
Wait… what? How is this possible?
Well, it could be precisely for the reason mentioned in Rachel’s original question: muscle is denser than fat.
1. Body composition 101: muscle vs. fat
Body composition refers to the relative percentages of fat and muscle in our body. It is an important concept in understanding how someone could be exercising but not losing weight.
At some point in your life, you may have heard someone say “Muscle is heavier than fat.” That’s incorrect (and it makes me think of that trick question, “Which is heavier, a pound of feathers or a pound of bricks?”) We all know, whether it’s a pound of feathers, bricks, muscle, or fat, a pound is a pound is a pound. That’s why it’s a trick question.
So it’s not that muscle is HEAVIER than fat. Muscle is DENSER than fat, as Rachel accurately pointed out. Muscle takes up less space, per pound, than fat does.
Let’s say I have very strange tastes and I ask you to gift me one pound of sand and one pound of bubble wrap. Which one will require a larger gift box? Or, look at this from the other side: imagine you bring two identical carry-on bags on vacation, one filled with bubble wrap and the other with sand. Both bags are full. Which one will be harder to lift into the overhead compartment?
Yup. The bag of sand will be much heavier than the same size bag of bubble wrap, because sand is denser than bubble wrap.
In fitness terms, muscle is the sand, and fat is the bubble wrap. Muscle tissue’s higher density means it takes up less space in your body than the same weight of fat. In fact, one pound of muscle takes up 15% less space than one pound of fat.
This means that when it comes to strength training, it’s possible to be exercising but not losing weight– or at least, not losing much. If you’re successfully gaining muscle and losing fat at the same time, the weight on the scale may decrease quite slowly, not budge at all, or even increase depending on how much muscle you add vs. how much fat you lose.
For this reason, if you’re trying to lose fat while also aggressively strength training, with proper progression, your weight on the scale is not the best tool to measure progress. It’s a useful data point, but it should take a back seat to body measurements, progress photos, and how your clothing fits.
If you are exercising to lose fat/change your body shape or composition, you’d be looking for your measurements to decrease over time, your clothing to get looser, and photographs taken over time to start to reflect a change in your appearance.
You should find yourself losing inches and noticing a difference in how you look, but depending on where you started, your weight on the scale might not change much at all.
So, the first question I’d ask someone like Rachel, who’s exercising but not losing weight (and desires weight loss), is: have you seen a change in your body/visible fat since you started strength training? Are your clothes getting looser? Are you happier with how you look?
If the answers to these questions are generally “yes,” then the issue probably isn’t a failure to lose fat, it’s simply an over-reliance on the scale.
In that case, just stop worrying about what the scale says and focus on the body composition metrics I mentioned.
2. You can’t out-exercise your nutrition
Ok, but what if you’re exercising but not losing weight on the scale –and not losing inches either?
This brings us to the second potential reason for exercising but not losing weight: you need to change your nutrition. (Please note that I’m specifically avoiding the word “diet” here because I don’t want to promote the idea of “dieting.” Nutrition implies lifestyle choices, not food restrictions and fads.)
People often make the mistake of thinking that if they just start going to the gym (whether they’re doing cardio or lifting weights) they will lose fat. That’s why so many moms feel compelled to run to the gym the day after pigging out at Thanksgiving, thinking they’re going to “burn it off.”
It doesn’t work that way.
In fact, while vigorous movement matters and is great for your heart, it’s a very small part of the equation if you’re trying to change your body composition. (Oh, and also, what you eat on a single day at Thanksgiving or Christmas has absolutely no impact on your body composition, so stop worrying about it.)
You may be surprised to learn that the vast majority of the calories you consume each day get used by your body simply to maintain its various processes that keep you alive.
While there are a few unusual exceptions, generally speaking, the math of fat loss and gain is pretty simple:
- If you consume more energy (in the form of food) than you use, also called a caloric surplus, you will gain fat.
- If you consume LESS energy–called a caloric deficit–than you use, you’ll lose fat.
It takes a caloric deficit (consuming less energy than you’re burning) of 3,500 calories to lose just one pound of fat.
But even the most vigorous cardio only burns a few hundred calories. As for strength training: well, my Apple watch said I only burned about 175 calories in my strength training session a few days ago, during which I worked very hard and lifted more than four tons in total weight.
Hopefully, you see where I’m going here.
What you eat–and more importantly, how much you eat, as measured in calories- accounts for about 80% of fat loss.
There’s a ubiquitous saying in the fitness industry, and it’s true: whether the exercise is strength training or cardio, “You can’t out-exercise bad nutrition.” (Another popular saying, “Abs are made in the kitchen,” is also true, for the same reasons; visible abs are almost entirely due to low body fat, and body fat is determined almost entirely by how much we eat.)
You can very easily be exercising but not losing weight if you’re eating more than you’re burning–and exercising just doesn’t burn that many calories.
Don’t misunderstand. Exercise is AMAZING. Everyone should exercise. BUT, if losing fat happens to be our goal, we have to focus most of our effort on taking in fewer calories in the first place, rather than trying to burn them after the fact. Most of the caloric deficit mentioned above has to be achieved through our nutrition.
The point of strength training isn’t to burn calories.
I want to stop here for a second to stress one point. Not everyone who lifts weights is trying to lose fat, but even if they are, lifting weights does not, in itself, burn a ton of calories. Lifting weights helps us preserve and put on muscle.
And while having muscle is important in all circumstances, it’s especially crucial if you’re trying to lose fat.
Why?
If you just cut your calories right now and do nothing else, you will lose weight, but up to 35% of that weight loss will be MUSCLE loss, not fat loss. You see, our bodies prefer to burn muscle over fat. Fat is energy that your body stores because it’s not needed right now, but might be needed later.
That’s biologically brilliant; we evolved to stay resilient and to be able to survive when food was scarce, which it often was until very recently in human history. But this evolutionary advantage means that our bodies will jealously hoard fat and happily burn muscle for energy unless we make it clear in no uncertain terms that we NEED that muscle.
When you strength train (and eat enough protein), your body responds by repairing and preserving your muscle. If you’re in a caloric deficit and strength training at the same time, when your body needs energy, it will use fat.
In fact, it’s been found that in the hours after a bout of strength training, your muscles release substances that jump-start the process of fat-burning in your body.
Also, both muscle and fat send out all kinds of chemical signals that affect metabolism, and the more muscle you have relative to fat, the more the balance of those chemicals tips to make your metabolism more efficient, meaning your body burns more energy at rest. But even this effect will be relatively small– certainly not enough that we can just eat whatever we like just because we’re strength training and putting on muscle.
The bottom line is that going to the gym and lifting weights (or doing cardio, for that matter) doesn’t burn a lot of calories, and it definitely won’t make up for eating in a caloric surplus.
Rachel didn’t mention food, so I can’t definitively answer the original question. However, if someone 1) is strength training and making progress/getting stronger, and 2) isn’t losing fat as determined by things like body size and shape (losing inches and looser clothes), then they’re probably not in a caloric deficit… and if losing fat is one of their goals, they’ll need to get into one.
If they are already supposedly in a caloric deficit, then either their target deficit isn’t large enough or (and this is much more common in my experience) they’re actually consuming more calories than they think they are, so the actual deficit is much smaller than what they intend.
How to achieve fat loss successfully, while supporting muscle preservation and growth, is a whole other topic and a question for another day, if someone decides to ask it. Wink wink.
Do you want to know more about why moms should lift weights? Want to know how to start? Or how to progress? Want to know other things about fitness, health, and wellness? Ask an Iron Mama will be a regular feature on Vermont Moms, so ask away!
Please submit questions for Miriam here. You can ask her anything, so have at it! Questions may be featured in upcoming articles.
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