How To Tell If Weight Gain Is Muscle Or Fat

how to tell if weight gain is muscle or fat

You are probably here because you are wondering ( aka, freaking out ) on how to tell if weight gain is muscle or fat.

Whether your goal is actually weight loss and that dreaded scale is going up, but you heard someone say “Ah you are probably just gaining muscle!”.

Or whether your goal is to build muscle but you want to make sure you don’t put on too much body fat in the process.

This article is going to clearly and concisely lay out exact how to tell if weight gain is muscle or fat, so stick around.

You can be rest assured that you can be feel confident knowing that you are in fact gaining muscle, or maybe you need to lay off some of the calories a bit.

Either way you will know, and that is the most important part.

Let’s get into it.

How To Tell If Weight Gain Is Muscle or Fat

Weight Loss / Gain vs Fat Loss / Gain

Before we get into specifics, I want to quickly touch on the difference between gaining or losing weight vs gaining or losing fat.

Yes, they can be two different things.

Our body weight is made up of so much more than just muscle and fat. Our weight on the scale holds our muscle, fat, internal organs, bone density, water weight, waste ( using the restroom! ), and more.

Therefore first you have to realize “weight gain” has so much more to do than just gaining or losing muscle vs fat.

You can lose 2lbs in like 5-15 minutes after you go #2 ( depending how long you like to poop for ).

Does that mean you lost fat? Absolutely not, you just removed some excess waste, so you have less content inside your body.

You could step on the scale and weight 200lbs.

If you step off the scale, drink 16oz of water, then immediately step back on, you are going to weigh 201lbs.

Did you gain fat OR muscle?

No, you now just have 16oz of water inside your body that your body did not have before.

You can gain and lose weight on the scale for a variety of reasons.

I did an entire video on exactly why your weight might fluctuate for any one of these reasons, you can check that out HERE if you want to learn more.

It is important you understand this because it will set us up for what we are going to hit on next.

It Takes Time

When it comes to how to tell if weight gain is muscle or fat, the unpopular truth it, it takes time to know.

I know, people don’t like that now a days. Not sure when you will read this, but as of right now Amazon basically makes it so you click two buttons and Jeff Bezos himself air drops your package through your roof.

We want things right meow.

The reality is when it comes to how to tell if you are gaining muscle or fat, you won’t know in a day.

Or a week.

Or even a month really! ( Okay, you will kind of know in a month, and we will touch on that soon ).

The point being is it takes time. This is because like we talked about above, your weight is going to fluctuate up and down for various reasons throughout the course of a week, two weeks, three weeks.

If you aren’t weighing yourself everyday ( which I believe you should be and HERE is why ) then you simply just won’t have enough data gathered in order to make the appropriate decision.

For example, one reason your weight might spike up the next day is because you had a meal that was higher in sodium the night before.

This would cause your body to store some extra water weight waking up the next morning.

Did you gain fat overnight? Absolutely not. Did you gain muscle overnight? Hell no, though I do wish it was that fast.

Point being, you can’t look at your weight on a day by day basis and make conclusions because it fluctuates so much.

This is why you get all of the data points for the month ( daily weigh ins ) and look at the trends.

This is a weight loss chart of one of my online coaching clients, but you will see what I mean here.

how to tell if weight gain is muscle or fat

Notice how she weighs herself everyday and there are fluctuations right?

But, look at the overall trend line, where is it going? Down, this means she is losing weight despite the fluctuations up at times.

Gaining muscle or fat is no different, one or two days doesn’t mean you gained muscle or fat.

You have to look at things from at least a 4 week perspective, otherwise you simply do not have enough data to make the proper conclusion we will talk about now.

How To Tell If Weight Gain Is Muscle or Fat : Track Your Data

You just heard me talk about above you need to give at least a 4 week time frame of tracking data in order to see if you are gaining fat or muscle.

But what does that data look like? What exactly do you track?

Well first off, I did an entire video on this, I can link it here if you want to watch.

Yet I am going to cover each thing you need to track for how to tell if weight gain is muscle or fat in detail here below.

There are four main things, bodyweight, measurements, progress pictures, and your workouts.

Let’s first start with bodyweight.


I mentioned earlier that I was a fan of tracking your bodyweight everyday for 4 weeks straight.

Why do I suggest this?

I talk more in depth about it HERE, and I also mentioned it above so I won’t go too in depth on it right this very second.

Essentially what you need is the most data you possibly can.

The more data you have, the better, and that is all your bodyweight is, data.

If you have 31 data points in a month from weighing yourself every single day, that is more data than say if you weighed yourself once a week for 4 data points a month.

Don’t you think you will be able to tell the overall trend better if you have 31 data points in a month instead of 4?

Yes, I agree! I believe so as well!

Therefore weighing yourself everyday, not looking at the day to day fluctuations, rather gathering the data and looking at it from a 4 week view is the most beneficial to tell if you are gaining muscle or fat.

So, How do you know if it is muscle or fat?

Great question. An average rate of muscle gain is going to be anywhere from .5-2lb per month.

Now let’s break this down and actually use it in context here.

This is where you can look at your data over the course of the last 31 days and analyze your trend.

If you started at 150, and 4 days in your weight spiked up to 154.

Yet, if you just stayed the course, kept going, and by the end of the 31 days you are averaging about a weight of 151-152, you would know that you are probably gaining mostly lean muscle mass. ( Provided you are strength training, which we will touch on here in a second! ).

Despite your weight having spikes or drops throughout the 4 week span, you gather the data and look at the overall trend of where you are heading.

If you are on pace to gain 4, 5, 6lbs per month, okay well there is no way you can gain muscle that quickly ( even with anabolic drugs ).

Therefore you are probably putting on a bit too much body fat and may want to decrease calories a bit.

Now, I will say this. I have had a lot of people come to me who were deliberately looking to go into a muscle definition phase. This means you typically want to up your calories into at the very least maintenance calories if not a calorie surplus.

Thus meaning when you initially bump up your calories, you very well could gain 4lbs in a month due to extra food in your stomach as well as extra carbohydrates storing some water.

In this scenario, if you are someone reading this who recently bumped your calories up, I would say you need to track your data for 8 weeks before knowing exactly if you are gaining muscle or fat.

This is because your weight is going to go up a bit initially but that does not mean you gained fat. You need to get that second months worth of data to see.

If you gained 4lbs in the first month and then 1.5 the second, well then you know you are gaining almost all lean muscle mass and minimal fat gain.

You just need to be sure to give it the time it needs to truly tell what is going on!


Now that you know what an average rate of weight gain would look like for muscle mass vs fat mass, let’s talk about measurements.

Yes, you should be tracking other things than just the scale, this is very critical.

I recommend you do what all of my online coaching clients do and that is track your measurements every two weeks.

What measurements should you track?

I would track your

  • waist ( You can even track above the belly button, below the belly button, and at the belly button )
  • Quads / thighs
  • Hips / glutes

Then, any other measurements you want to take whether it be arms, chest, back, etc if you have specific areas you want to focus here.

Here is the thing, and stick with me here because I am going to try and explain this the best I can.

Let’s say your goal is weight loss, but you see that scale isn’t going down or even going up.

You may think you aren’t losing fat. Well, hold on champ, this is why you take measurements.

If your goal is weight loss and you are taking your measurements, if they are going down but the scale is not, you are losing fat and building muscle at the same time.

Which, is really hard to do, so huge congrats.

The reason is because muscle is more dense than fat, which means it takes up less space on your body.

If it takes up less space, then your measurements are going to go down and your body will look different ( we will talk about this more in progress pics ).

This is a good thing! So the next time you get discouraged over the scale, remember this.

If Your Goal Is Muscle Gain

Then when it comes to measurements your measurements may very well increase, and that would be okay because you are looking to build muscle in certain areas.

Here is what I would say though, even if your goal is muscle gain, you want to make sure you are not putting on too much body fat.

How do you make sure of this? This is why you track your waist measurements.

It is one thing for your glute measurement to increase or your thigh, but throughout the process your waist measurement should be either staying about the same or increasing at a very slight rate.

Meaning if you are gaining 2-3 inches per month on your waist, you are probably over doing it and putting on a bit too much body fat.

While if you are either maintaining or gaining say .25-.5 per month, that would be an average rate of gain for muscle gain progress.

Again, more so because there is more food and carbs in your system rather than gaining fat.

Waist measurements are one of if not the best indicator of fat loss / gain progress, so taking your measurements every 2 weeks and keeping an eye on them can help make sure you are not over doing it.

Progress Pics

The third, and my favorite way of how to tell if weight gain is muscle or fat is progress pictures.

Simply because, the pictures don’t lie baby.

Numbers like bodyweight and measurements are cool and I believe important to have data on, but nothing is going to trump side by side progress pics.

Take one of my clients Bremer here below.

how to tell if weight gain is muscle or fat Bremer pic

I don’t need numbers to know this dude completely changed his physique.

One of the toughest things about changing your body is that you see yourself everyday so you can’t tell these small changes happening.

But, if you take progress pics and put them side by side very 4 weeks, you are going to see changes that you did not know were there.

This is why no matter what the data says if you look at your progress pics and you are looking better, you are gaining muscle and not fat sweetie.

It is just important to actually take them. I’m being serious.

The amount of people who will read this and be like “oh yea for sure!” Then not go and do it is astounding.

Don’t be one of those because that means you are more than likely going to become a slave to the scale.

Which, we both know, is not fun at all. Nor is it smart at all.

Strength Training Workouts

Let’s say you still aren’t 100% sure of whether you are gaining muscle or fat.

Perfect, here is where we look at your workouts.

First off, just so we are clear, the only way to gain muscle is through following a proper workout program.

Unlike losing fat for example where all you havve to do is eat in a calorie deficit, if you are not working out, there is physiologically no way your body is going to build muscle.

So if you aren’t working out and you are gaining weight over an extended period of time.. Yea, probably fat.

Second, yes, you should be tracking the workouts you are doing. One of the most underrated things to look at by far when it comes to changing your body.

Why? Let’s talk about it.

The way your body build muscle is through something called progressive overload.

I wrote an entire article on that HERE if you want to check it out. It is very in depth so I will keep it short and sweet here.

Progressive overload basically just means you are doing more over a period of time.

Therefore if you are tracking your workouts and you are doing more reps, more weight, getting a bigger range of motion, literally anything positive in the right direction.

You can bet your bottom dollar you are building muscle.

This is the first thing I look at when looking at clients, before I look at bodyweight, measurements, or even progress pictures, I look at their workouts to see if they are doing more reps, lifting more weight, etc.

If 4 weeks ago you were lifting 40lbs for 8 reps, then now you are lifting 50lbs off 8 reps, your body had to overcome a stress and get better to lift more weight.

Aka it had to build some muscle!

If you gained say 1lb over that 4 week span, I can now be 100% sure that lb is muscle because your workouts prove to me you are getting stronger and doing more.

But if you are lifting the same weight, for the same reps, with the same form, and nothing is improving while gaining 4lbs per month?

Yea, that is more than likely fat gain as well.

Therefore tracking your workouts is a great tool for you to use to have data in order to tell if you are gaining muscle or fat.

How To Tell If Weight Gain Is Muscle or Fat? Q&A

Now that we laid out exactly how to tell if weight gain is muscle or fat, let’s look at some most common questions.

If I Am Gaining Body Fat, What Do I Do?!

Well, it is hard for me to tell you 100% for sure without knowing your exact situation.

But, typically speaking, if you are gaining too much body fat you would need to decrease your calorie intake.

You could also play around with your macro intake specifically, meaning protein, carbs, and fats.

I did an entire video on how to optimize muscle building and minimal fat gaining HERE if you want to check that out for yourself.

But long story short, you will have to cut back on your food intake.

What If I Am Trying To Lose Weight?!

As we mentioned previously in this article, you can lose fat without losing weight on the scale.

This is called body recomposition and it is actually really hard to do.

What this essentially means is you are losing fat and building muscle at the same time.

No you are not replacing muscle with fat, and no muscle does not weight more than fat, you are simply losing fat and building muscle.

For example, if you lose 3lbs of fat but gain 3lbs of muscle, the scale isn’t going to move.

Yet like we said, since muscle is more dense than fat, it will take up less space on your body, you will look different, and you will feel so much better.

This is why you need to be tracking all four of the forms of progress we talked about, not just your bodyweight, because that thing will lie more than I did when I was 12 years old telling my mom the dishes were done.

Who Should Be Looking To Build Muscle?


Plain and simple, I believe everyone should be looking to build muscle.

From the person looking to be a bodybuilder to the 70 year old looking to keep the quality of their life.

Now, not everyone has to go the extreme of being a bodybuilder ( and trust me, it is hard as hell, so you won’t unless you really dedicate your life to it ).

Yet I do believe everyone should be training to build lean muscle mass whether your goal is longevity, health, an aesthetic, lean, defined physique.

You can’t just build a ton of lean muscle mass by accident and look like Arnold the next morning.

Again, trust me, I wish it was that easy.

Therefore training for lean muscle mass gains is something that is going to positively benefit you now with a more lean, defined physique.

As well as later on with a higher metabolism, more bone density, improved insulin sensitivity, to name a few.

How To Tell If Weight Gain Is Muscle Or Fat : That’s A Wrap!

I hope you enjoyed this article on how to tell if weight gain is muscle or fat.

There are a few distinct markers you can and should look to in order to truly know the answer.

But remember, it takes time. You won’t know in a week or two. Track your data, do it over time, then look at trends and be able to tell.

Hope this helped and look to chat soon.