Principle behind cardio AM on an empty stomach?

[gymbud]

Hi guys,

I've read some conflicting information and I'm wondering if someone could explain to me the principle behind some folks advocating cardio on an empty stomach in the morning. The negative I can think of is that this could trigger protein catabolism -- but perhaps due to the overnight fast it is irrelevant? Anyone care to elaborate?

Thanks.

[terraj]

Pre- breakfast cardio has been embraced by bodybuilders as a tried and true fat loss technique, however there is definitely not a unanimous agreement on this.

For me......I want food as soon as a get up, I like my cardio late in the day....however if I were ever to try to get to single digit body fats levels, I would maybe ....maybe do pre-breakfast cardio on some BCAAs

[Dr.Roidz]

This is extremely debatable as terraj said. Even the statement of just using BCAAs sparks debate as to whether or not they hinder fat burning. The bottom line is we worry so much about the specifics we sometimes forget the basics. just do cardio period. its going to benefit you regardless.

[bigslick7878]

I have found through trial and error that cardio on empty is FAR more effective (for me at least) for fat loss than doing it at other times. I saw weight loss doing it at other various times but there was some muscle loss too, much more than when I was strictly doing it on empty. The only time I do cardio now iis in the morning when I wake up. Throw in some BCAA's with about 10 min left and you will be fine, and the fat will melt off.

[jypoll]

the basic principle is that since you havent eaten you have no food to burn so you must be burning fat and not breakfast

[gymbud]

the basic principle is that since you havent eaten you have no food to burn so you must be burning fat and not breakfast

the bolded part is what I'm not sure about. yes, of course you can't burn something you haven't taken in. But because the body is in a "fast" mode.. there's two things to also consider here : (1) if you're fastening and you start using a lot of energy, does the body try to burn stored fat first or do stored carbs and proteins become a better option? Carbs seem a bit less likely as you wont have that much left in your body.... so fat vs protein..and as far as what i can tell from online sources is that fat will be burned through ketosis but that there may be a miniscule amount of protein also needed. so it seem that herein is the benefit.

and (2) since you've now exercised while in starvation, what will your body do with the food you take in after the cardio? here im not so sure what the answer would be.. but I can imagine its probably better to eat high protein, low-med carb as you'd want to make it as difficult as possible for the body to store it is fat... so perhaps on these cardio days, lower carb in the morning and then add some of that to the second meal?

regardless, as the others have mentioned, i dont think we have a clear cut answer except that it seems to work well for folks trying to reach sub10% BF.

[jypoll]

yes i suppose your body wont be able to "choose" between fat and muscle, so you will end up burning some of both, but it will end up decreasing BF%, but you may have a hard time packing on more muscle if this a regular event in your training