This doesn't really answer your question but I don't eat anything before working out and I don't drink a shake either.
I know some people need to eat something or drink a shake or else they might feel weak during their workout but I have never had a problem with my energy level during any workout, even Body Max 2 at 97 minutes. I am able to make it the whole way through without eating or drinking anything (except water
).
Also, I have read in several different sources that doing cardio in a fasting mode can actually increase your fat burn slightly.
I know it is recommended to eat before doing heavy weights but I have never had problems with doing that either. I work out very early in the morning (3:30 am) and there is no way I am getting up earlier just so I can eat and then let it settle and then finally start my workout!
However, with that I think it is just as important or maybe more important to eat after your workout. After any heavy weight workout (not circuit workouts), I drink a protein shake within 30 minutes after working out to help my on-the-mend muscles.
So I guess, if you don't need to eat anything before hand for energy reasons, then I wouldn't worry about it. If you do need to eat for energy reasons, hopefully my response will bump this so someone else can help you.
Hope that helped!