Dad is on a "see food" diet. If the food is there, he will eat it.
I first noticed this last Christmas. On Christmas Eve our family celebrates with a Swedish smorgasbord. Generally I begin with hors d'oeuvres items, then I add items to the table; first some breads and cold cuts, then meat balls and potato salad, and finally dessert. We each dish up a small plate of food and sit in the living room, and begin the gift exchanges, going back for new foods as they are set out.
To begin with I had a selection of cheeses, herring and crackers on the table. Dad enjoyed the herring. In fact, we couldn't get him away from that end of the table. He stood there, helping himself to piece after piece of herring and crackers, until he couldn't eat any more.
Not too long ago we went out to lunch with some friends. Dad had a burger with all of the fixings. He also had a very clean plate when he was finished. He ate everything, every crumb, every piece of the tomato and every little bit of each leaf of lettuce. Oh, and he also would have eaten my dessert had I let him!
When I have been visiting him, he will often ask Judy what they will be having for dinner. When she responds, he will say, "Let's go!" He is ready to eat, even though it may only be 2:00 PM. Many times as I come in and sit down he will ask when we are heading out to the restaurant for dinner. He gets so disappointed when I explain that we won't be going out, that I will be heading home to make dinner for my husband and myself.
Dad and Judy came for a lovely Thanksgiving dinner. He enjoyed his meal and was always an eager participant in seconds! But, I purposely did not begin with appetizers and we served the food buffet style, so the serving dishes were out of sight... and mostly out of mind!
I am theorizing that some of the behavior I am noticing may be due to the fact that Dad was always a busy man, and he now finds reading, working on the computer or writing too difficult to attend to. Therefore, nothing is occupying his time, so... might as well eat!