Instructions
Begin a new game and select a female character. You will begin the game as a child and grow to an adult after playing through the prologue to the story.
Spend points in character traits other than "Strength." While a strong character will have better melee attacks, she will also put on a great deal of muscle bulk as her level increases. Instead, give your character strong magic or ranged attacks by placing points in "Will" and "Skill." This will keep her thin and lithe.
Use potions and healing spells to heal your character instead of food items. Eating too many food items will cause her to gain weight.
Feed your character celery, which can be bought from any vegetable seller and most food stands. Celery causes your character to lose weight and will heal her without having her gaining any weight.
Sell any food items that you come across that are not celery so that you have more money to afford healing potions instead.