So, first off, I want to preface this by saying that this is all still a plan, and hasn't been implemented yet, so please, let us know how you feel about it.
Alright, the basic idea is that you'll have a stamina gauge of some sort, that will slowly decrease throughout the day, not unlike Shenmue III, but not tied to your movement or your HP. This gauge actually affects when you go home at the end of the night, within a 2 hour window. So if you don't eat throughout the day, Ryo will be famished/tired by 9PM, and will go home then (aside from nights where the story dictates you be out late, of course), and different foods restore different amounts of the meter. So if you've only eaten a few things, and you've got like 25% of the stamina gauge left, Ryo will go home around like 9:30, and if you have like 50%, he'll go home around 10:00, and so on and so forth. It's a simple system, but as I see it, it adds incentive to eat, while being minimally intrusive. It also allows us to really flesh out the food establishments, and even gives a use to things such as chocolate and potato chips beyond giving you a drawing in the raffle at the Tomato Store.