Abilities are supposed to do more good than bad, but Gluttony does more bad than good. You get 10HP for each food item you eat but your belly goes down twice as fast as a result.
My suggestion is to have belly go down at a rate that could be countered better by a Stamina Band. Currently even with Stamina Band, Belly would still go down faster than average. Since most players equip items such as bands and scarves it would be at the cost of not being able to equip items.
Feel free to comment/criticize.