Explain 'burning muscle'...?

Lolli1986

There is a lot of mention of burning muscle and how to avoid it. Can anyone explain exactly what this means and the mechanism of muscle burning?

I'm a biologist, so go as technical in your response as you want.

I was asking a vet student (lol, hush, it's still a biologist) the mechanism of mucle-bulking and he said he was not certain, but thought that increased muscle size is caused by increasing the size of striated cells, not the amount of cells.

So what is this 'burning muscle'? Does it refer to the breakdown of glycogen, or the breakdown of proteins, or what? And when/why do we start burning muscle when there is plenty of freely available fat in adjacent cells?

Why would certain calorie deficits or make-up (eg protein:carbs:fats) trigger muscle burning?

mandylooo

I think it's just muscle loss. If your calorie intake is too far below your calorie usage then you end up not just losing the fat you want to get rid of, but the muscle as well. When people try to lose weight too rapidly this is generally the result.

Lolli1986

I guess the question is how and why do we lose that muscle?

Is it just that when we lose weight there is less weight to move around, so muscles get smaller?

Or is there something good stored in the muscles cells being burned that we don't want to burn.

I guess i'm just curious because my leg muscles are massive and remain that way regardless of whether I am 150lbs or 125lbs. Whatever this phenomenon is, I have not experienced it, so I am curious.

tabi26

I'm no expert and have no complicated technical answer for you lol. But what I've learned on MFP and by researching myself is that if you're eating at a deficit and not lifting heavy-ish weights then while you're losing weight you're also losing muscle ( about 20%-25% of muscle).

Also, pretty sure the reason your body burns off some muscle is because you're not "feeding it enough" and muscle burns more calories than fat. I think I read somewhere that one pound of fat uses about 5-10 calories a day to maintain itself and one pound of muscle uses about 40-50 calories a day to maintain itself. So IF that's correct, then when in a deficit it would make sense to your body to "eat up" some of the muscle to "keep you alive". less muscle means it would take less food to keep you going.

Not sure really if I'm right, but I do lift weights to try to offset that 20%-25% muscle loss. Will I gain muscle in a deficit? Very likely not, but my goal for now is just to hold onto as much of it as I can and when I reach my goal weight maybe do a "bulk/cut" cycle and see how that works out.

ilovedeadlifts

I guess the question is how and why do we lose that muscle?

In a simple form, the same way you lose fat.

If your body is at a caloric deficit, it needs energy and has to use fat/muscle as the energy source.
Your body prefers to keep fat, it's higher in cals, therefore more critical to have in an emergency (without food for days), so it also uses muscle.

Lolli1986

bump.

Thanks heaps for your answers. It's restating the things I've read around and sort of makes sense.

Still wondering what it is in the muscle cells that is being burned away.

mandylooo

The same things which are in every cell in the human body, fat, and protein. Every cell wall is made up of fats and with muscle the fibres are protein. The human body can break down both fat and protein and use them for energy. If you eat too little, your body will turn to the protein in your muscles for energy.