Hi DaniM83. Most people here continue with their normal exercise routine after the first couple of weeks getting used to the lower calories. I am not quite sure whether you normally eat before your 5.45 am exercise (are you mad!!!!) but you still can if you want to count it as a snack. I have never done an intermittent fast as I am diabetic and would fall over? What I have found is that I have had to adjust my exercise so they occur half an hour or so after eating. So I exercise around 1 hour after breakfast or one hour after lunch. As you are not diabetic and will not be suffering from hypoglycaemia to a dangerous level, you can still continue as usual.
The main thing is to remember, you cannot add extra calories to compensate for exercise. You have to make your exercise work around the diet. Your body will get rid of the low calories.