Opinions and results on fasted cardio?

Primarily personal preference. Some people find their performance suffers a bit if they don't have a bit of fuel at the start, others don't. Just gotta find which you prefer and go with it.

I don't know that I see better results or anything but I run 3-4 miles as soon as I'm up and dressed a couple of mornings each week, including this morning. I don't eat breakfast until I am at my desk at work.

On the weekends I run longer and I'll usually eat something that's mostly carbs a half hour or so before I start. I find I don't do as well on runs longer than 75 minutes without a little something in the tank.

http://www.bodybuilding.com/fun/the-myth-of-cardio-before-breakfast-debunked.html

i can do it for a couple of days (rarely deliberate) but nothing long term. the past 2 or 3 days i think i did, mainly because i was at the gym earlier than normal, and i cant eat when i first get up.

I checked with running world (magazine and website) as I had a similar question since I am a noob at running.

I ran at 5:20 pm yesterday but made sure I had a small snack about an hour before...per the magazine as it indicated (which I know from my experience weight lifting) eating something an hour or two before exercise can be beneficial for that workout and your energy levels.

I tried once when it was too early for breakfast... had a horrible workout. No thanks.

It is hard to give an opinion without understanding your objectives.

If the idea is "weight loss", I think the evidence tends to indicate it doesn't help much. But it does produce other changes - namely, in the ability to process fat as fuel (instead of carbs) at different exertion levels. For most athletes that's meaningless - you do your soccer game, run, or crossfit in an hour. Done and done. You have enough fuel for these short activities pretty much at any point.

Are your runs 2+ hours? Or your bike rides? Then you might want to improve this capacity to use fat as fuel - a male athlete can hold about 2,000 calories in glycogen (easily available energy). Then you run out and bonk, unless you're eating. But if you're exercising heavily it's not like you can have a donut, half a cup of ice cream and some bacon without it coming up. So you're limited to about 60 g of carbs/hour - that's absorption rate, and seems independent of body size. So it benefits you if you "train" your body to use fat as fuel at higher intensity. One way is by getting generally fitter (better aerobic capacity). The other is by fasted training.

For the latter in my case it is 2+ hours on coffee and nothing else. Moderate intensity, see how it goes. If you try high intensity intervals you're probably going to end up on the side of the road hallucinating. Pack a sugary snack for such an emergency But long steady burns? I do these about once or twice per month. It feels a bit weird and you certainly can feel the "hangry" sometimes when you're approaching the empty mark.

Again, this is not for weight loss, it is an aspect of training for endurance events, especially those that intersperse high (i.e. carb-fueled) intensity efforts across a long session. Like sprinting on hills during a race.


One well respected pro-team doctor's view:
http://home.trainingpeaks.com/blog/article/the-importance-of-carbohydrates-and-glycogen-for-a

I really don't have choice. Exercise with food in my stomach means food coming back up out of my stomach.

I'm a morning exerciser and not a morning eater. It's just what works best for me.

If I go to the gym before work in the morning, I simply cannot eat. I already feel ill if I eat too soon after waking up, so eating, and then going to the gym would probably make me vomit all over everyone.

However, when I get home from the gym, I need to eat DIRECTLY after walking through the door.