I do not think it matters when you take in your calories, I think we discussed that here or elsewhere.

However, I have seen results of blood tests they did on a bunch of athletes. They sent them out on a max. 90 minutes ride before breakfast and they saw an increase in free fatty acids in the blood i.e. fat was being used. A cup of coffee (make that black, no starbucks junk in there) increased the effect.

More than 90 minutes and you run into trouble.

I have a feeling most of us hobby riders (myself included) have the tendency to overcompensate for what we burn. I have caught myself snacking probably more than necessary before exercise so I don't bonk .