To make Ronda fat you need to:
- Give her the bulking powder and the discontinued energy drinks
- Trick Eve at the gym into gaining weight
- Wait for Eve to lose the kickboxing tournament
- Convince Eve to become a sumo wrestler
- Wait for Eve to win the sumo tournament
- Talk to Bonnie who will give you a 'special' item for 'bulking' that instead of giving Ronda muscles (like usual) will make her incredibly fat instead.
Olivia doesn't get fat, her boobs get bigger based on how many maids you recruit for her.