Originally Posted by 5kgLifter
intense cardio (HIIT) on an empty stomach can leave you recovering for hours in addition to affecting the amount of intensity you can apply to the session due to not having the energy reserves for the higher intensity.
I believe this helped cause me to crash a few weeks ago. Intense fasted cardio, combined with a restricted contest prep diet, not enough rest, etc.
Also begin to affect my training as i was not able to recover as fast as i needed to.
As others said, personal preference, just be careful.