I'd like to open this up for discussion / debate. Rick87 stopped by my training log last week and asked why I do fasted cardio. My response is below, but I'd like to put this out there where others will see it and be able to give their 2 cents. Agree with me, disagree with me, call me out on BS, whatever. Either way I think this could make for a very informational thread.
No need to apologize. Assuming your reason for doing cardio is for fat loss and not cardiovascular health or endurance, I would have to say doing it first thing in the morning, on an empty stomach is the most effective way to burn fat while maintaining muscle mass.
Think about it. Lets say you wake up at 6 am, train at 9 am, and do cardio at 6 pm. By now you've got several meals in. You're not burning fat, you're burning calories from the meals you just ate today!
I'm also not a fan of postworkout cardio. Call it "broscience" or whatever, but I think it's one of the most catabolic things you can do. I lost a lot of muscle mass during the first few weeks of my last prep and it may have been because my cals were too low, but I think a lot of it had to do with the fact that I was doing postworkout cardio. I have no scientific studies to back that up, it's just my opinion.
Another reason I think fasted is the best, is because it keeps your metabolism going all day. I don't have any links to share, but there have been studies done that show fasted cardio keeps you in some sort of fat burning state for several hours after you're done. If you look, I'm sure you can find some supportive information out there. It's also a great way to start the day. By doing cardio first thing in the morning, you are setting the tone for your mental state that day. Remember, the mind is a powerful thing.