Daily exercise when your body is starving

S

sophienaz

New member
Hi,

Ok I have a potentially controversial issue to discuss....

What happens to your body when you are eating very few calories, yet are doing daily exercise?

I understand that if you do no exercise and eat less calories than you should, one's body goes into what is referred to as "starvation mode" and after a certain while, the body mass plateaus and there is no further weight loss.

Now, what happens if a person of average weight and average height is doing daily exercise, and is eating say, 1500 calories a day, when realistically they should be eating, say, 2200 calories per day? (I apologise for the rough estimation of numbers)

Do they actually put on muscle or do they burn more fat, or.....both?

Thanks in advance for any help...

:)
 
in no expert, but its my understanding you would loose more weight initially, but because your body would be in starvation mode your body wouldnt be getting the nutrients it needs to build muscle or metabolize fat and because of that you would start to feel lousy and you wouldnt be able to maintain that lifestyle and if you did have the will power to do so eventually you would stop seeing any benefit from it.
 
The body will preferentially use gluconeogenesis (look it up for more information) to produce glucose before it uses lipolysis (Lipolysis - Wikipedia, the free encyclopedia) which breaks down fat when you FIRST start working out.

in the first 20 minutes or so of exercise, your body rushes to keep up with the increased demand for carbs (which I will call glucose from now on). After the first 20 minutes or so, the body will start to look for other sources of glucose other than the bloodstream, so it will send out signals to enter the body into lipolysis (fat conversion to glucose).

If you are not eating enough, and your body has no glucose in the bloodstream to begin with when you begin exercising, the body will enter gluconeogenesis, the burning of "protein" aka muscle to get the glucose level up initially, because gluconeogensis is "cheaper" for the body, fat burning costs more energy, and takes longer. Your body is an adaptation machine, so if it thinks you are running from your life from a saber tooth tiger, it will provide the quickest, cheapest energy which is from muscle (assuming you have no glucose in your bloodstream from starvation)...

Now, if you are eating healthy, when you start working out there will be ample glucose in the bloodstream to use for starting the exercise, then your body can consume fat stores after the first 20 minutes or so. This is why diets like the Atkins are so stupid, because your body will lose weight fast, but a higher percentage of the weight to begin with is muscle.

This is just a coarse summary, I am sure some people will want more detailed information, and it's possible. I just didn't want to sound like a cell biology book!

-Mellon
 
You very rarely gain muscle while dieting. How much you burn is going to primarily be affected by two things - how much protein you eat, and how much 'moving heavy things' you do.

There's a lot of research on what happens specifically during cardio and what substrates are burned, but from what I've read it seems that it all evens out over the course of the day. So if for example you burn lots of glycogen in some high intensity exercise, and even break down some muscle tissue, during the time when you're not exercising, your body will be using more fat than it would to make up for the deficit.

If you don't get enough protein, then your body won't be able to rebuild muscle, because protein is the raw building block. Protein is even more important in low carb approaches where it has to do double duty and is converted into glucose for the biological processes that require it.

Moving heavy things also matters, because the stress on the muscles is what sends a message to your body that you need the muscles. Otherwise it assumes they're just optional. But if you're pushing your muscles a couple times a week, the body adapts and retains more.

There's nothing really dangerous about exercising when you're at a 700 calorie deficit as you describe, and it's even better if you're doing weight bearing exercises.
 
Thanks for all the responses, very helpful. I think having adequate glucose in the bloodstream and glycogen in the muscles/liver prior to working out is of vital importance. It is terrible to eat muscle whilst working out, what a waste, after all the hard work that is being put into it.
Thanks again.
 
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