Gaining

Maybe she thinks that you don't like the extra weight, so you should at least let her know that you don't mind the extra weight. From that reaction, you can let her know you actually prefer her heavier. She may be relieved and eat more. As long as you don't push her, she should not mind.

I would love if a man did this to mee! Just do what you feel and she will love it 😊

Help her stay in denial about how much she's eating and how fat she's getting. Never acknowledge that she's putting on weight. In fact, tell her she's looking fit and ask if she's lost weight?

If she moans that she ate cookies, tell her a fit girl like her can stand to have a few cookies, it's no big deal. And make sure she can feel how hard you are for her "fit" body.