What you are giving him now might be what is turning him off to food... but you didn't say anything about his current diet, so it's difficult to know. In light of this, I would like to make some general suggestions about his unwillingness to eat "anything":
Stop giving filler foods like chips, puffs, cereal, toaster waffles, corn syrup-based "maple" syrup, pasta, cookies and bread. He will stop eating altogether for a while (a day) which may feel alarming to you, but it will go away.
Present him with all natural foods: sliced fruit, berries, melons for breakfast on day 1. This will stimulate his appetite. He'll be very hungry for something more substantial well before lunch.
Put food out for him while he plays (rather than putting him in a high-chair) and let him snack throughout the day. Small kids don't eat "lunch", they generally snack since they are so busy.
Snacks can be whole grain crackers, cheese, dried fruit, lots of fresh fruit, baby carrots, avocado chunks, nut-butter on bread/toast...
Dinner should be what ever you feed yourself minus any dessert unless the dessert is fresh fruit.
Once you have eliminated filler foods, his system will enjoy the flavors of whole foods again. Filler foods contain sweeteners, dyes and corn syrup which spike insulin production. This, unfortunately, sends a message to the brain: "MORE!" Then this is all we want to eat.
Most of us don't realize the impact of filler foods because we are sold them everywhere we go for breakfast, lunch and dinner.
Pack fresh fruit, raisins and whole-food snacks when you leave the house and let go of the idea of a 'meal'... he'll eat when he is good and hungry.