Is there a way to prevent dizziness during exercise, or is it something you just have to deal with until you're fit enough it's not a problem any more?

My experience with dizziness during exercise is only when I am overdoing it. If you are working that hard, you have likely moved into the anaerobic range. A bit less strenuous will be more effective for weight loss, and you can work your way up as you grow stronger. Just my 2 cents.

The trouble is, this is mostly during team practices and a fencing class I'm taking, so I have to show good effort. I was just wondering if there was some little trick to it I was missing, but if not, it's not that bad. I'm not having a serious problem working through it, it's just unpleasant.

I'm not a doctor or anything, but it sounds like something you might want to tell your coach/instructor about. I don't tend to get dizzy from exercise, so to me it doesn't sound like just a little trifle that you should work through.

The couple of times I got dizzy when working out it was because I hadn't eaten properly or wasn't well hydrated....

I actually came on this morning to post the same thing. I've been working out pretty regularly since January and would consider myself an advanced intermediate. I've upped my workout length and intensity in the past few weeks and have been doing really well and seeing results on the scale, which is awesome.

Last week I was fine, doing my Cathe DVD's every morning for 50-70 minutes a pop, modifying when needed, no problem. But yesterday and today I struggled with keeping up for maybe 30-40 minutes tops before I just got too dizzy to continue. I don't know what's changed between Friday and Sunday, but I'm a little concerned. I don't really like to eat before I work out, because it's sooo early, I'm working out at 5am, but I might have to dry it, although I don't know what I would eat. Would a piece of fruit and some water be okay?

A banana is one of the only things I'll eat before working out, because it gives you quick energy but doesn't necessarily sit in your stomach and give you that "heavy" feeling. If you're eating 30 mins before a workout, oatmeal is good - but if you're working out at 5 AM, I doubt you're up 30 mins before you start working out.

Maybe you could also try eating something before bed so you're not so nutrient-starved when you wake up?