As it is now, some really good food items have really low full and fed up values (think autumn delight), while some crappy recipes have insanely long 2h+ values.
Overall, it seems a bit random, if not counterintuitive.
As you said yourself on release, values are probably up for some tweaking still;
Why not make the full and fed up time directly proportional to the amount of biles you would gain (on all bars) if you gluttoned the food item with no invariance penalties? Or to it's added values at 0% purity? Or even, proportional to the actual amount of biles gained in all bars upon consumption?