At least in Pathfinder 1e, the couple times Gluttony or similar is mentioned, it’s very limited. The examples I recall are a couple mentions in Cursed Items, or Flawed Magical items. In both instances, they only state that the user of the item must eat more food than normal or suffer the effects of Starvation.
As I mentioned in my rules, there is a official feat and prestige class in Pathfinder 1e that required the character to be obese - the Bloodmage (or Bloatmage). It wasn’t a core class, and from the best I can tell, it has never been updated to Pathfinder 2e. That’d definitely be something you could look at adding for your rules. For reference, you can look up the Bloatmage HERE