I have no idea how Gluttony is supposed to work to begin with. xD I'm actually more annoyed with how big of a hit I take from eatting mushrooms. I cannot wait until I'm able to start actually farming.
I just got carpentry, but I'm still spending most of my time wandering around trying to forage for foods. I know that getting the Flowers and Berries skill will help greatly there, but its just taking forever to get up to the level to get it.
Brief gluttony explanation, then!
If you click the little forks below your bars it'll activate gluttony mode. In that mode, you can eat whatever you want, it won't give back any biles, but it will fill up a corresponding bar irregardless. If you mouse over a food it'll tell you how much it'll fill up. So like, the upper right bar is blood, the lower left bar is yellow bile, etc.
When this bar hits the top in gluttony mode, you get an extra max point in that bile. However, if you eat a lot of the same foods (a lot of berries, for instance), effectiveness drops off. This isn't such a big deal early on (and good thing too, about all you get is berries at that point), but I expect it'll be a big deal later on.
Biles are, for reference, Phlegm, which is your stamina, blood, which is your HP, Yellow Bile, which is your "combat" meter (the higher your current yellow bile is the more damage you do and the less damage you take), annnnd black bile which you spend to study things and start building buildings. Black bile also effects the amount of inspiration you get back over time. They're all very important! And I think like in haven and hearth, the gluttony meters all use the highest value for a bile you have. So if you grind up yellow bile, the rest of your biles are going to be that much harder to raise.
The more you eat during gluttony (irregardless of whether a bar goes up or not), the longer it'll be before you can activate gluttony again.
You can sorta tell what will give what by mousing over outside of gluttony mode, but it's a terrible interface and I regularly forget how to translate it. Early on, mousing over foods should suffice.