Beila, I have no answers because I'm doing 24-hour fasts and I don't have any expertise to tell you. My instinct would be to say that exercise is good any time you can do it, but you might find it more effective/intuitive/necessary to eat after high-intensity workouts.
But what do I know? I'm going to a flow yoga class in 40 minutes and will be fasting another 6-8 hours after that.
Last night was rougher than I would have liked. Writing on an empty stomach was fine, but then I dreamt of food -- not really of food, but of eating. Woke up feeling guilty before I realized all my noshing was imaginary. Weighed in at 117.5, a low for me, but I'm fairly sure it was just an empty-stomach dip, so it doesn't 'count.'
Still, though, Eat-Stop-Eat fasts can be a bit brutal. I don't think it makes sense to sugar-coat that... you do get really up close & personal with your hunger. I may be a masochist, but I kind of like that.
I think a lot of us are tempted toward over-restriction and get into unhealthy cycles as a result. One way of dealing with that is eating small meals on the dot in a very regulated way -- I've never been successful with that, given my hectic schedule, inability to cook (as a student in dining halls), and compulsive tendencies. I'm hoping these fasts will allow me to get all my masochistic, overachieving impulses out in a controlled, safe way.