well this is one of those things that we can argue for 50 pages so it depends on who you want to listen to
i will give my opinion based on my own experiences and what i've learned from the most trusted guys, interviewing them on my podcast and everything. i can tell you for example Frank Zane when I interviewed him absolutely lived off of fasted cardio every morning. he credits that for keeping him super lean
again as i said above you always want to do cardio fasted, otherwise your body will want to evacuate what is in your body. plus less stress on the body
but in terms of fat it does speed up glycogen loss, so lets say you wake up.. hydrate and then do cardio.. then wait to eat until very much later in the day. the beauty part is you can take advantage of both the cardio and the fasting (with fasting your metabolic rate does not drop) so it is a double whammy. that isn't all though. for those who believe the bullshit that you will 'lose gains'.. the nice thing is if you fast for 10+ hours you will get a sharp rise in HGH which will prevent muscle wasting
i always do my cardio in the morning and then fast for 14-24 hours after for this reason for my goals