I commute from Amsterdam to Utrecht (92km return), and that is about the longest ride I can do without a snack. If I know I'm going to be out for more than a 100km, I'll plan on eating a few hundred calories (sandwich/banana/nuts) every couple of hours, a real meal about every 8-12 hours and as much water/tomato juice as I can stomach. For anything under 300km I'll generally not stop for a meal. If I eat more than that I usually encounter digestive unpleasantness. The big thing is to get your body used to digesting food while you are riding. It took me a few brevets to figure out what and how much I could stomach.
For a century around here I'll pack a couple sandwiches, a pack of stroopwafels and a few bananas. I usually come back with the stroopwafels, but they are nice to have in case you can't find an AH or whatever.
There is a randonneur club in the Netherlands:
http://www.ern-ossendrecht.nl/ if you are interested in that sort of thing.