While there has been some press lately on how exercising before versus after a meal may affect calories burned and weight management, people with diabetes have additional considerations. For me, I have generally avoided exercising soon after a meal simply because I'd rather not deal with the conundrum of either taking my normal bolus and crashing from the insulin once it becomes super-active during exercise or underbolusing and then going high early on. This was especially noticeable with running, and I tried to never have more than 1 U of insulin floating around when I went out the door. For races or other times when I want to have a meal beforehand, I try to bolus & eat about 3 hours prior to starting to exercise. Then, I am able to take a full bolus that is pretty much gone by the time I start.
But today, for various, uninteresting reasons, I wanted to eat before my 1-hour easy ride. So I thought I would experiment a little. I took my full bolus and ate my normal breakfast. But when I took my bolus I also shut my pump off for an hour. Hmm, maybe it was 90 minutes. At any rate, by the time I started my ride, my pump had been off for 45 to 60 minutes; although I had a full bolus still peaking. My BG was somewhere in the low 100s and rose up a bit; I checked about 40 minutes in and it was starting to fall, so I ate a 20g gel. By the time I finished, I was 160; I took a correction bolus and settled in nicely in the low 100s.
I still prefer to exercise with just a snack versus a whole meal, but it was nice to figure out a way to sneak in a ride post meal in case I need to do that again. I think if it had been a much harder ride, I may have had a bit of trouble. Also, since I don't normally shut my pump off (or even modify basal rates) during exercise, I have some room to play with my basal rates. I guess, in the past, I have used this method if I had to take a correction bolus close to exercising; although usually I just take a smaller correction than I might have otherwise done.