Size and Weight Gain

Size is your character's, well, size. Their mass. Their weight. Their surface area. Your character's size increases after eating a meal that puts their current Fullness past their Max. Fullness. Every 6 Sizes, your character goes up a Stage. With each Stage, your character gains special benefits or downsides. Depending on your Quirk, your Stage might impact those as well.

Stage Size Effect
Unhindered 1-6 None
Strained 7-12 -1 Dexterity, +1 Constitution
Hindered 13-18 Strained Effects, -1 Willpower, +1 Force
Greatly Hindered 19-24 -Adv Dexterity, -1 Willpower, -1 to all rolls if Fullness is empty, +2 Cooking
Sub-Mobile 25-30 -Adv ATH & Willpower, -1 to all rolls if Fullness is below half, Adv Constitution & Force
Immobile 31-36 Unable to roll ATH or Willpower, -1 to all rolls if Fullness isn't at Max, Unaffected by downsides of meals, Adv Cooking

Losing Weight

There are two main ways to lose weight that don't involve outside tools like Spells or certain meals: Exercise and not eating.

Exercise is performing any ATH roll with the Healthy Status Effect. Perform A Successful ATH roll or successfully win a combat encounter without taking damage with the Healthy Status Effect, and you go down a Size.

Whenever you perform an action, such as making a roll, or engaging in Combat, your current Fullness goes down by 1. If your Fullness is at 0 for 3 actions, then you gain the Hungry Status. Go 6 actions without eating, and you gain the Starving Status. When you're starving, any action afterwards when at a Fullness of 0 will make you go down a Size.

If you're Immobile, then you instead roll 1d6 to struggle about until the physical exertion forces you to lose weight and go down Sizes equal to the number you rolled.