Sunday, February 05, 2017

Burning Muscle

I posted this on Facebook yesterday and there was quite a response – debate, agreement and even outrage:
Interesting. I've been reading stuff about weight loss and exercise etc for quite a while now. Some of the things I kept coming across are, 'Don't eat too little or your body will go into starvation mode! It'll burn muscle to preserve itself! It'll retain fat!' I raised an eyebrow at this because it made no logical sense. The body is a fast machine for the transmission of slow genes. When food is plentiful it stores it as fat. When food isn't plentiful it burns that fat. Surely? Yes it does. Starvation mode is a myth, probably from people who inhabit that world where squirting coffee up your bum is a good idea.
Note: I mean here 'starvation mode' in the world of the fad diet whereby some believe the body burns muscle in preference to fat.
So, apparently, the theory is this: if you fast, your body undergoes changes to utilize its resources more efficiently. It burns up the supplies in the liver and then turns to glycerol in the fat and amino acids in the muscles. After two or three days it switches over to ketosis i.e. it stops burning any muscle and instead burns up fat stores. Or … it starts laying down fat and burns muscle. Or just within a day it starts doing that. Or…

You see the problem.

This stuff is rife with contradictions and fallacies and my goodness you mustn’t go into ‘starvation mode’ and experience ‘muscle wasting’. When I start reading emotive terms like that my bullshit radar comes on and starts beeping. The immediate mental image that arises is of people staggering out of Auschwitz or skeletal children in some African village. The problem here is that the internet is a breeding ground for the apocryphal and that ninety per cent of what you read is from somebody who has an angle, or a repetition of the same. Try the turnip and mealworm diet to avoid starvation mode and muscle wasting! The majority of the stuff you’ll read about diets, nutrition and exercise sits on the borderland of real science where self-appointed experts sell their snake oil. And all of this gets promulgated by people repeating stuff they want to believe (confirmation bias) and thus creating memes that are not necessarily true.

In the end you have to go back to first principles. What are we? We are fast machines for the transmission of slow genes evolved over millions of years by and for that purpose. The biological machines that are us take in energy to power us (food), ensure that we are capable of simply staying alive and gathering more food, and breed. That is all evolution requires of us. So, apply that logic to the above.

Is it logical that we would burn off muscle before fat? That we would experience ‘muscle wasting’? Does it make any sense to sacrifice the machine in preference to the fuel supply?
No, not really. Yes there might be a small loss, but in that respect I would go with the school of thought that says your body starts catabolising cells that are damaged, not functioning correctly or redundant (autophagy). That makes sense – there was no imperative to deal with that mess while our guts were providing a bounty of nutrients.

Yes, muscle wasting does happen, and it happens when your body runs out of its usual food, that is, what is in your guts, liver and fat stores. It happens when you go below minimum body fat, which, beside the relocation camp victim, is something that can apply to body builders too. Your body does start eating itself to stay alive – almost certainly in order of importance i.e. the muscle in your biceps will go before the muscle in your heart. But this is irrelevant to the world of the fad diet and Joe Public (very few of whom are at the low end of body fat and very few of whom are likely to go without food for days on end), and the ‘burning your own muscle’ meme is an overblown scare story.

I think the reality is this: Strict diets and fasting in the healthy will only cause problems in THOSE WHO DON’T NEED THEM.  

1 comment:

J Eddy said...

Hi Neal,
I had a discussion about muscle wastage a while back, and it was explained to me like this:
Your body can store excess energy as fat, but can't do the same with protein.
When you need energy, your body will take it from food in your system, or from fat storage, whichever is easiest to liberate.
When you stress muscles, such as with exercise, they are damaged and need to be repaired. Because spare protein isn't stored, you pull protein from your food intake, BUT if you haven't got any in your system when the body needs it, it'll scavenge it from less-vital muscles.
So your body won't destroy muscle for energy, but it will to rebuild a muscle that is stressed, the theory being that if you're stressing that muscle, you need it to operate better.
This is also why protein powders are popular, even with the If It Fits Your Macros crowd, a steak or a head of broccoli might have the same protein content as a shake, but it takes your body longer to break the protein down into something it can use. Or you could blend a steak or protein rich vegetables, but that's up to you.
Again, this is as related by a PHD student, and according to my memory, so I may have screwed it up somewhere, but it made sense to me at the time.