Im a little confused.. I was told by my P.T. to start doing my cardio in the morning on an empty stomach. Ive done it in the past and have to say- the results were there. However, Im trying to lean up as well as maintain muscle mass. Will cardio on an empty stomach interfere with muscle growth? Im under the impression that right when you wake up, being as though your body is in famine, you should eat! On the other hand, im a curvy girl, endomorph i believe. I could probably use the extra fat burning on an empty stomach. but im also concerned i may be hindering muscular growth by not fueling my body right when i wake up... any thoughts on this matter?
Thanks!

Tara

Yes you could potentially affect muscle growth, and yes you could potentially burn muscle.

Frankly I've seen reports of healthy people using that method, and getting dizzy spells, and one person trying it, and flagging badly on a Cardio workout.

Cardio on empty, when you think about it makes little sense. You are doing Cardio, (known to lower Bloodsugar), then doing that when your Bloodsugar is already low first thing, and expecting it's going to be okay.

If you ate something then did Cardio, the body would attempt to burn the Calories, not other things like Muscle. Yes it would mean Fat stores would be left alone as well, (no Ketone production, unless the meal had little to no Carbs), but realistically the only way to even attempt to get round the no muscle burn, fat loss scenario, would be to take a Protein shake, (low Carb kind), before hand, and feed the muscles to protect them from Catabolism, but low Carb means Ketone production to strip Fat, but then without Carbs, you could still get issues with low Bloodsugar, and the body attempting to lower it thus further.

Neither I nor I suspect you, could know, if that would create a short-term or long-term problem, but I'd be very loathed to say it's perfectly fine.

I did read somewhere once someone complaining of Abdominal discomfort during Cardio, and saying running on empty stopped it, because the body wasn't channeling blood to the Stomach area, or some such reason, due to there being no food in the Stomach. A rehashed description of what their trainer told them. Can't attest to how accurate that is though.

Yet I don't see any reason to do Cardio on empty.

If you can like many people probably can, sustain low bf%, without doing it then don't. Like I say, doing something known to lower Bloodsugar when levels are already low, is possibly playing with fire, and if not now, then possibly the future.

I like doing cardio on an "empty stomach". As long as your goals are fat burning and not performance based. Even then I would always advise using amino acids before hand. 5-20 grams of BCAA's or a serving of low carb protein shake with water like Boss mentioned. So if you are training for an athletic event, eat before hand. If it's for burning off belly fat, first thing with a little supply of Aminos in the bood before hand does wonders.

it's not really on an empty stomach then is it?

Technically not no, but the stomach is more empty than say consuming a meal. Plus the BCAA's would digest quicker, and there would be less of an enzymatic reaction, if there was no need for the stomach to produce one or more Carbohydrate enzymes.