Quote Originally Posted by ono View Post
If you're doing cardio on an empty stomach i would advise doing low intensity for somewhere in the region of 30 mins. Anything other than low intensity will lead to muscle loss (a lot). By low intensity i mean walking (quite a fast pace).
I'm not sure I agree with this. High intesity exercise like sprints will increase muscle mass in your legs. What is low intensity will depend on how fit you are so it doesn't have to mean walking.

I also would say that while I don't usually have a problem eating small amounts before an intense workout most people will have issues if they eat within an hour immediately before a hard workout. I wouldn't say that exercising hard on an empty stomach is bad as long as you don't feel drained. I would often leave breakfast until after my harder morning workouts if I do it early enough - say 5 or 6 am.