PSA: Muscle vs. Fat

>> Monday, March 29, 2010

I feel like I'm doing a disservice to all of humanity if I don't address this "myth". I use quotation marks because it's not really a myth - just a misunderstanding or misconception.

Statement: Muscle weighs more than fat. FALSE!

Okay, here's the skinny. First, we need a few definitions to establish our baseline understanding.

Weight: (n) (1) A measure of the heaviness of an object. (2) the force in which an object is pulled towards the earth - therefore the product of the objects mass and acceleration of gravity. (mass x 32.174 ft/s^2) {sidenote: my physics professor used to always say "That is NOT seconds squared. That is feet per second per second." LOL so it's a velocity per second... hmmm}



Mass: (n) A property of matter equal to the measure of an object's resistance to changes in either the speed or direction of its motion. The mass of an object is not dependent on gravity and therefore is different from but proportional to its weight. {This is the physics definition. There are several others, including "The sacrament of the Eucharist"}

So, since mass has no dependence on gravitational forces - your mass stays the same whether you're on Earth or the moon or Jupiter. Your weight, on the other hand, will vary greatly due to the differences in gravitational forces on those planets.



Some of the confusion between "mass" and "weight" comes in because "MrsB - they have the same units of measure! So why aren't they the same?!" Well, technically speaking - the units of measure are NOT the same but Americans are lazy. There is a difference between a "POUND FORCE" (lb-f) and a "POUND MASS" (lb-m). (The "f" and "m" are usually subscripts). What's the difference? Gravity.

Here's where the rub gets even better - due to the definition of gravity on Earth and the way these constants were set up - when you take your weight {on Earth AT sea level} and convert it to your mass {on Earth AT seal level} - they will be equal.

Us lazy engineers would say "You multiply your weight by "g over g sub c". In other words, you multiply your weight by the gravitational pull of the planet you are on divided by gravitational constant (32.174 [(lb-m*ft)/s^2]/lb-f). So everything cancels out and you are multiplying by "1".

Still with me? Hope so. Here's where the good information comes in.


Density: The measure of how much MASS per unit volume. So simply put - if mass is how much "stuff" there is, density is how tightly packed that "stuff" is.

Density is the reason that muscle does NOT weigh more than fat. Muscle does NOT have more mass than fat either. Muscle is more tightly packed than fat - therefore it is more dense - therefore it takes up less SPACE.

Here's my best example: You have 5 pounds of feathers and you have a 5 pound bowling ball. If you put them both on a scale - how much will each one weight? Right - they will both WEIGH 5 pounds. BUT the bowling ball takes up less space (or volume) than the feathers. Sure, you could jam all the feathers into a box and they will take up less space than a pile of feathers...but then the 5 pounds of feathers became more dense.

So if you're telling yourself that the number on the scale keeps going up because muscle weighs more than fat - then you are lying to yourself. If you are like "But my clothes are so big and the scale hasn't budged!" - then you are probably putting on muscle and burning the fat off.

If the scale is going up and you're doing all the right things - you could be in the middle ground. Sometimes you put on a little bit of muscle underneath your layer of fat and then you're still working on burning off that fat. The muscle helps your metabolism and helps you burn that stored fat...so keep building muscles!

Clear as mud? :) If you're still confused - please feel free to ask questions. I will do my best to answer them. :)

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1 comments:

Amy March 29, 2010 at 3:03 PM  

Even though i had to read this post like, 6 times, it was a good thing to hear. I've been going up on the scale and really worried about it!

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