I have a list of foods I commonly serve that I give to my parents with a contract, so they can write yes or no or notes like "only with ketchup" or "won't eat if the peel is on," etc. This worked until I got one 4-year-old temporarily over the summer who apparently "hasn't tried" almost all fruits and vegetables. The mom just wrote "hasn't tried yet" on about 90% of them. Then at the bottom she added notes that included "really likes pizza" and notes about which soda the child likes the best. It was unbelievable. I'd still suggest getting a list, just be prepared for what you might get back!
Also, I have a 5 year old dcb who claims he doesn't want snack or isn't hungry on a regular basis, I think because what I'm serving might not be his favourite thing, but once he sees everyone else eating it and he doesn't get anything else he usually changes his tune. Do your other dckids eat with/in front of him?
I agree with 5 little monkeys, at least he's trying it, but I hate wasting food too! Good luck!