The other thing
@shoesy24 when you combine a fast with exercise is BGs can rise before they fall again. I do a lot of swimming and Aqua Fit and the gym every so often. It was pretty disheartening to spend 45 mins in the gym and have your BGs rise. Basically, your body was looking for something instant to burn to make up for the energy expended. So, no food and your liver dumps into the system hence the BGS rise. I used to counter it by eating something like an oatcake (which I wouldn't do now I must admit) and it worked. As
@Chook says though you get used to it and so does your body. I did an Aqua Fit class, had a swim and 30 mins of water running today and all I had was a lot of water. BGs dropped as they should.