If we believe what the bible says then there was this piece of fruit that made us more aware of who we are and what´s going on, also after eating that piece of fruit people started having sex with eachother. So maybe it wasn´t so bad to eat it? Anyway food seems to play a role during sex (for some people), from thinking about to actually eating or using it for pleasure. Some people actually get turned on by food, though I´d rather not think about how that would look.
Your parents probably told you as a child that you shouldn´t play with your food, well it seems that some people do like to play with their food and do naughty things like sticking a banana in their exit hole. Now that might be a bit extreme but some consider that as pleasure, though some people also consider eating a delicious steak as pleasure. But just sticking food in certain places doesn´t mean that´s all to it, some people rub grapes in someones face or put whipped cream on their nipples.
The good thing of food is that it´s not hard to get it and the prices are often reasonable, so instead of getting a dildo you get a banana. The problem with food is that it won´t stay good for long, so it would always be a temporarily thing. Personally I have a problem with using food for pleasure, I mean I like pleasure like everyone else but using food for that seems like a waste. Because when I pleasure myself with a banana I don´t feel like eating it anymore, though some might disagree and still eat it. So imagine that banana to be inside someone else, that doesn´t make it more appealing for me to eat!
What I find interesting about this fetish is that some people seem to be ashamed for it. Even when they know the other also has some kinky fetishes, people with a food fetish still seem to be reserved talking about their food fetish. Which is ridiculous, because who doesn´t like to lick some whipped cream from nipples? If you´re honest and have an understanding partner they´ll be more accepting then you´d think. Though you might have to do something for them as well, but that only seems fair to me!