re: Is your S/O fat? Would you ever tell him/her to get in better shape?

Change your diet and only eat well. This will create two critical events to happen. 1. There will be better food to eat at home and as she's preparing your healthy meal, she'll end up eating the same food. It'll get to be too much to cook two different meals. 2. She'll feel guilty when your eating grilled chicken and she's eating fried chicken.

Cliff notes - Guilt