Is it a good idea to give my dog some leftovers?

My vet said to cut my 5 month old knee hight 11kg mix breed's meals down to 2 a day, one in the morning and one at about 5-6 o'clock. He said we can give him a snack in the evening. Would it be a good idea to give him something suitable? For example, today i had Chili Con Carne. Would it have been ok if i had given him some of the left overs? I think it would be a good idea to hide it and put it in his bowl so he doesn't know he's getting human food (he's not allowed in the dining area while we're eating, he goes in his crate). Is rice ok for a dog? Are there any human foods that are definitely NOT ok for a dog? Thanks.