The amount of food people eat during a ride is dependent on how many miles per year they have in their legs and on how hard they ride. One of the effects of aerobic training is to increase the rider's ability to burn fat on the bike. When riders are first starting out, is it normal for them to have to eat as frequently as every half hour. As their fat burning and glycogen access improves, they need to eat less frequently and in smaller amounts. The harder one rides, the more metabolism shifts from fat burning to burning glycogen. We have a limited amount of glycogen available in our muscles and liver, about 2000 calories. Everyone's amount of available glycogen and rate of fat burning is different and changes with amount and type of training. The purpose of the long training rides leading up to a century is mostly to sort out saddle, food, and hydration issues. You need to find what foods and how much of them your body can tolerate.

For a relatively short ride like a century, it's not necessary to eat a lot while on the bike. As digger says, it's more important not to overeat. Personally, I find it most important to eat during the first three hours, about 200 cal./hr. If I do that, and then eat more when I feel hungry, I'm going to have a good ride. If it's a supported century, with rest stops, I tend not to eat at the rest stops, rather grab a bar or two or some such, put it in my pocket, refill my bottles, and then dribble in the calories on the bike as I get hungry. It's not good to eat too much at once.

It used to be said, "Eat before you're hungry, drink before you're thirsty." I may do that for the first 3 hours, but then I do the opposite: eat when I'm hungry, drink when I'm thirsty. Besides that, I drink by frequency of peeing. I like to have to urinate about every 2 - 3 hours. More frequently = drinking too much, less frequently = drink more right now.

It is a good idea to have a recovery beverage or meal or combination after a ride, just as the OP says. This is to replenish glycogen. I find it best to start immediately after the ride, and then space out the calories over the next couple of hours, rather than eating a big meal right away. IMO glycogen replacement is the same for everyone, whatever their bodyfat percentage.

As others have pointed out, pretty much no matter how much you try to eat while on the bike, you're going to burn calories faster than you can take them in, leading to weight loss. The more miles you ride/week, the more weight you'll lose. I find that I am less likely to overeat after a long ride and the next day if I stay fueled while on the bike. YMMV