T Nation

Muscle & Fat

Does anyone know the makeup of muscle & fat?

I know muscle is 72% water. How many percent is muscle fiber/protein and how many percent is glycogen? Is there anything else?

What about fat? Does it store water and glycogen as well?

I’ll post the results when I get home, but I do have the answer for you. Initially, there is some water in adipose tissue, but no glycogen.

i dont think you can really answer this. as sarcoplasmic hypertrophy would increase the holding of glycogen and fluids. plus i think the different fiber types have inherently different makeups

These are the results from a study by Martin et al. “Adipose tissue density, estimated adipose lipid fraction and whole body adiposity in male cadavers” Int. J. of Obesity. 1994. V.18, pp.79-83.

I have read several papers by this research group and they are the current authority on the chemical composition of the human body based on cadaver dissection. This study looked at adipose tissue composition (lipid + water + residual). Lipid and water generally make up greater than 90% of this mass, so I will ingnore the residual component. Their study showed that if you had a lower % body fat, you had a greater proportion of water in the adipose tissue. If you had a greater %body fat, you had much less water in the adipose tissue. Here are the results from the six cadavers:

1)17.8%body fat (%BF), adipose water fraction (AWF) - .363, adipose lipid fraction (ALF) - .540

2)23.4%BF, AWF-.321,ALF-.638
3)27.1%BF,AWF-.286,ALF-.638
4)27.8%BF,AWF-.249,ALF-.685
5)30.1%BF,AWF-.184,ALF-.767
6)43.9%BF,AWF-.118,ALF-.850

Basically, the fatter you are, the more your adipose tissue is triglyceride.

I'll take a look for the exact composition of muscle, but for reference: lean body mass is approximately: 73.8% water, 19.4% protein, and 6.8% mineral. This is definately not carved in stone and to see the reasons why these assumptions are not perfect check out my articles on body composition.

Thanks for ine detailed info Jason. Much appreciated.

I forgot to ask. Which part would glycogen be under - water or mineral? And how many percent is that? I’ve read in another post that the average person has about 600g of stored glycogen (liver and muscle)?

Well, glycogen is really a separate component, but it is usually so small that it is not accounted for. Where you see glycogen making the biggest impact is in the water content of lean body mass. For each 1g of glycogen stored, 2.7g of water is stored also. So in essence, lean body mass is really the sum of water, protein, mineral, glycogen and cell residue. The last two are usually ignored for practical purposes.

BTW, I don't have the exact composition of muscle, but I know that people have done work in this area. I would assume it is probably similar to lean body mass in general, but you would not have the osseous mineral. That leaves about 2% mineral, 20% protein and 78% water, but that is just a quick guesstimate. You'll have to find a paper with the exact breakdown. I thought I had one, but most just look at fat and lean body mass as a whole.

Jason, with muscle having so little glycogen, what would warrant 50g of simple carbs after a workout?

I forget the exact amount, but glycogen storage probably ranges from 400g to 1000g per person depending on size. If glycogen stores are topped out, this ranges from about 1 to 2 lbs total weight. This is generally less than 1% of total body weight, which is why it is usually ignored. With that being said, we can easily use up 50g of glycogen during a hard workout and usually even more, so we definately need to replenish those stores after exercise.

Jason, thanks again!