We’ve all heard it: muscle is more dense than fat. I’m not here to argue that point, I’m here to point out that the internet is wrong. I know, shocker.
There’s about seven billion versions of this image when you look up fat vs muscle:
Holy crap, what a difference! It’s obvious what the point is: transfer your fat into muscle and you will take up a lot less space and therefore look better and feel better. That’s what they want you to think. I want you to exercise because you’ll feel better and feeling better is good.
So why do I need to get cantankerous about this? Why not just let it go?
When I saw this picture, my bullshit senses started tingling. It just doesn’t seem right, since these things are both like 70% water, there shouldn’t be a doubling of size between them. At this point I decided to get scientific about it all. I know, get excited!
I did some searching and found the following datas:
Muscle density: 1.06 g/mL
Fat density: 0.92 g/mL.
So the difference in density between the two is about 15%. This really confirmed what I suspected, that the size difference in that picture is probably really wrong.
After a fierce discussion with a coworker, the following picture was presented:
Some dude from some other internet site went to his local butcher and got a pound of fat and a pound of steak (muscle) and put them in a measuring cup. The point of this is clear: I’m wrong because here’s muscle and fat and it definitely looks like it’s twice the size. Grudgingly, I was about to admit defeat. If the math and science prove me wrong, I’m happy to admit that I’m wrong and either move on or figure out why I’m not wrong and go at it again.
As you might expect, I just had to figure out what was wrong with this picture. It took a few days of not really thinking about it, but then I had a realization: I can calculate the density of the fat and muscle in the measuring cups because I know the mass (1 pound = 454 grams) and I know the volume. The definition of density is mass/volume (hence grams/milliliter above). So let’s do this thing:
First the fat on the left. If you take a close look, the fat fills the cup to about 500 mL. If you think I’m wrong, feel free to do your own math as you follow along. So we’ve got about 1 pound = 454 grams divided by 450 mL gives us a density of 454/500 = 0.91 g/mL. The density for fat that I dug up was 0.92 g/mL, so hey that’s pretty good! Pat on the back for everyone.
Now for the measuring cup of steak, our muscle surrogate. Let’s say there’s 250 mL of steak as a round guess. Doing the same math as above we get 454 grams into 250 mL gives a density of 454/250 = 1.82 g/mL. Comparing that to the number I dug up for the density of muscle there is a huge difference between 1.82 g/mL for steak and the 1.06 g/mL for human muscle.
Sorry measuring cup guy, you’re just providing more misleading information. Dumb ass.
By the way: when I’m wrong about stuff, please point it out and remind me I’m a dumb ass. At least the former, maybe less so the latter. I can dish it out, but I can’t take it.
So that leaves only one thing left for someone who just can’t let it go: math.
What I want to know is this: what does it really look like when something with a density of 0.92 g/mL and something with a density of 1.06 g/mL are placed side by side? I started out by doing the math on 5 pounds of the material, but then realized that was a lot so I cut it down to 0.05 pounds of fat or muscle. For reference, 0.05 pounds is 22.7 grams.
I said before that density is defined as mass divided by volume. If we pull out some algebra or “math magic”, we find that volume is defined by mass divided by density. Using the 22.7 grams and knowing our densities as 0.92 g/mL for fat and 1.06 g/mL for muscle:
Fat: volume = 22.7 g / 0.92 g/mL = 24.7 mL.
Muscle: volume = 22.7 g / 1.06 g/mL = 21.4 mL.
Great, so now we have more numbers. Math is dumb.
However, I work in an analytical chemistry lab where we have a way to measure out this amount of water very accurately using what is know as Class A labware. So I measured out 24.7 mL of water into one tube, and 21.4 mL of water into another tube to show what the difference would look like between the same weight of fat and muscle:
I mean, there’s a difference but it’s a hell of a lot different from that first picture, isn’t it? So there’s my only point here: that first picture is really misleading and the measuring cup picture is just wrong. I realize only now that I don’t have the graduations that show the volumes showing, but feel free to perform a similar experiment at home using tablespoons or whatever you have available. It will at least be similar to this, I promise you.
I’m going to quickly address the people who are calling me out for using water in the tubes instead of fat and muscle respectively: it doesn’t matter what I used in the tubes, I’m just showing a volume. I could have just put a line on the tubes at the 24.7 mL line to fat and at the 21.4 mL line for muscle and the result would be the same. I could fill it to those marks with antimatter or plasma or Bose-Einstein Condensates or neutron star and so long as the volumes are 24.7 mL and 21.4 mL my point remains the same.
So quit looking at that stupid shit on the internet. You just wasted time reading this that you could have been tying up your running shoes or tuning the brakes on your bike or picking up and setting down heavy objects repeatedly. Too many times people argue about what supplement is best or what vitamins when they’re missing the main point: go outside, get sweaty. You’ll look better and you’ll feel better. Then do that three times a week forever. Bang on.