Jolie wrote: I've been thinking about coinciding fasting with exercise classes, however they are at the end of the day (6pm ish) and usually I would save all my calories for dinner (after the classes finish). Is it ok to do it on a totally empty stomach, or should I have something (100-200 cals worth) before hand to keep me going?
You'll probably be fine. Just make sure that you're well hydrated before you start - and perhaps take a banana or a small carton of choc milk with you just in case you feel that you need to eat before heading home. That's what I did before my first set of evening classes but didn't actually need it.
If you haven't been fasting long, then you might want to wait until a normal fast day is easy (i.e. your body switches energy source easily) before you start doing serious exercise on a fast day. But, as an example, I now cycle to work in the morning (6.5miles), cycle to the gym (1 mile), do 45 minutes Body Pump, 45 minutes of Body Combat, cycle home again (7 miles) and then have dinner. And still feel OK.
One other thing though, when I started exercising on fast days (other than my regular cycle) I did find that I needed to have two feed days between fasts rather than just one. Otherwise, the second fast day of the week became tougher.