Okay, I’m going to write up some spoilers for this guy so read at your own discretion:
The way that ‘???’ works is that for every coin you spend on it, the food is worth that many calories divided by 10 with the added bonus that it doesn’t effect the subject’s fullness. This was SUPPOSED to work for the late game when you have more money than you know what to do with, but as it stands it’s actually really underwhelming and I apologize. In the next update, I already have it programmed that the calorie amount is no longer divided by 10, so you could look forward to that, along with many other secrets.