You've got the Vienna Diner, used to be Dolly's just east of where the trail crosses highway 45. Decent local home cooked food with home made pies. The more commercial places, McDonalds, Subway are further east on 45.
Then you've got everything in Harrisburg but that's considerably further up the trail.
Between the Wetlands center and Karnak, well kind of, is Las Marias, a pretty decent Mexican restaurant. You have to realize, there's not a lot down that way. There might be a little place in Karnak but it comes and goes so often, I never count on it being open. Hope this helps.