Difference between caloric deficit caused by excercise and by diet

[a-n-i]

Hi,

I was wondering if there was a difference caused by a caloric deficit caused by exercise, and one caused by diet. I'm wondering because the caloric deficit that can be caused by endurance cardio like cycling seems a lot higher than the 500 kcal per day people recommend to avoid muscle loss. For example, if my BMR was 2000, and I ate 2500 kcal but burnt 2000 through biking, I'd have created a 1500 kcal deficit right? Does this mean I'd be burning muscle if I didn't tailor my caloric intake to ensure I got 500 less than my expenditure or what?

Thanks and sorry for the long post

[Pat]

Well, that depends.

When you exercise, you burn either carbohydrate (glycogen) or fat. When you burn fat, you need twice as much oxygen to get the same amount of energy out as you do for carbohydrate. When you are exercising hard, the oxygen supply to your muscles is limited by how much oxygen your blood can deliver so you will burn almost nothing but carbohydrates then.

Also your nervous system can burn ONLY carbohydrates. So if your brain is to live, you HAVE TO HAVE carbohydrates and if you burnt them all up, your body will rip up some muscle to make some carbohydrate - hey it is better then being brain dead.

So it is how you get to that deficit that is important and also what you are eating. If you burn mainly carbohydrate in your work out and consume mainly fat in your diet, then your body would seem to have no choice but to catabolize, fancy word for breaking them down, muscles to get carbohydrates.

On the other hand, if you exercise in a way to burn fat, less intense exercise, and you consume carbohydrates in your diet, you probably will not end up losing muscle.

I managed to lose 10 lbs in 2 weeks on a tour in the rocky mountains (lots of miles and lots of climbing) and I ate a carbohydrate rich diet and I generally avoided red lining it when I was riding and I seemed to lose only fat. Of course, experiences can vary.

[Richard Cranium]

A,

Yes there is a difference in "how you diet" to avoid "muscle loss".

You are right that two different people could lose or save muscle tissue differently, even with the same caloric deficit.

To avoid muscle loss, always eat small meals at regularly spaced times. Avoid long period with no food.

Sip, watered down energy drinks (carbohydrates) while exercising. The key point is to always have enough carbohydrate present to maintain your own energy and ability to "burn fat" without breaking down proteins. (muscle)

Good Luck.