The important thing is not to try too much in the first few weeks whilst your body is getting used to things - then slowly build up and always stay in a region where your feel ok. You are not taking in many calories - some people can exercise heavily on that and others not at all. I'm one of those people who carried on walking but apart from that didn't do exercise during the weight loss. Now that I'm refeeding I'm drastically upping the exercise. Do what feels right for your body.