Gluttony causes the Pokémon to eat Berries that would normally be eaten at 25% HP or lower to be eaten at 50% HP or lower instead. It has no effect on Berries that activate at other HP thresholds (such as the Oran Berry, which is normally eaten at 50% HP or less) or Berries with non-HP-related trigger conditions (such as the Leppa Berry and Lum Berry).
This section is incomplete. Please feel free to edit this section to add missing information and complete it. Reason: Gen IX
Please note that this is only 100% accurate to Generation IX games.
For Generation III games, ignore Abilities introduced in Generation IV or later and Hidden Abilities.
For Generation IV games, ignore Hidden Abilities.
For Generation V games, ignore Abilities introduced in Generation VI or later.
For Generation VI games, ignore Abilities introduced in Generation VII or later.
For Generation VII games, ignore Abilities introduced in Generation VIII or later.
For Generation VIII games, ignore Abilities introduced in Generation IX or later.
In other games
Pokémon Mystery Dungeon
In the Explorers series and Mystery Dungeon (WiiWare) games, Gluttony causes the Belly of the Pokémon with this Ability to empty out twice as fast. However, it also grants both benefits of Survival IQ skill - 50% chance to consume Grimy Food with no ill effects and 10% more Belly gain.
From Gates to Infinity onward, Gluttony heals 25 HP when the Pokémon eats or drinks an item.