This Thread touches on a couple different mechanics, which I think could be split into a few categories, like
Calories: how much energy do you have stored in fat, how much does any food give, etc.
perhaps have a period of time before energy from food turns into fat. once you’re hungry or very hungry, you would not progress further, but use up fat instead.
and
Nutrition:this could be a hidden set of numbers that together affect your health stat over time. this would use protein,bad_fats,good_fats,etc. the better your overall spread of diet, the better your long-term health, but there would be little short-term impact.
just 2c