Does Fasted Cardio Destroy Muscle?

[123456789]

If I do cardio before breakfast

but after I'm done I eat

then will I lose my gains?

 

Thanks

[SFRL]

Watch for the ammonia smell. If you smell like ammonia during or after excercise then your body has been burning muscle for energy. 

[Garuda]

depends if you are in a calorie deficit 

[CMacD]

Maybe a bit, but if you are strength training you are still going to build more muscle over the recovery period than what may have broken down during the cardio, as long as you are getting adequate protein & carbohydrates for your weight and activity level over the long term. 

If you aren't strength training I could see muscle & strength atrophying faster with heavy fasted cardio than it would just being lazy maybe, though.

Edited July 11, 2019 by CMacD

[pluto]

No.

[Michael569]

The hierarchy of ATP production from endogenous sources is as following: 
blood sugar -> glycogen stores -> fat stores -> protein stores. 

Your body will not break down muscle unless it absolutely has to. That being said, if your diet is low on Essential Amino Acids,  you will start breaking down your lean tissue because these cannot be created. This will not mean muscle but you may be breaking other tissues depending on the concentration of the amino acid you need. This can happen in any state not just in fasted though. A typical undereating diet, anorexia or eating disorder will eventually lead to this. 

ALso if your body's capabilities to transaminate (change one amino acid to another) are poor or you are low on cofactors that allow this (B6, Magnesium, zinc...) then you may start breaking down lean tissue again. 

But for a healthy well fed individual, fasted cardio will not do any of this.  Loss of muscle is often related to lack of stress or reduced exercise intensity or a disease state. Ageing is another one where that can happen. 

Edited July 12, 2019 by Michael569