Do NOT insist. Ask him if he wants the food.
If he doesn't then insist that he remains at the table until all are finished. If he takes food and doesn't eat it, put it in the refrigerator and warm it up for the next meal. Do not substitute; hunger will win in the end. Be "cruel" to be "kind". You are responsible for providing food but it is the child that eats it or not -- his decision.