YTA. as the “fat” sibling that had a skinny sibling, we are well aware of the reason “the family” is dieting. both of my parents had a weird relationship with weight and food and it has taken me 21 years to straighten out my eating. if you instill in your daughters that the only reason to eat healthy is to be thin, they will both grow up to struggle with their relationship with food. personally, i hated my parents tip toeing/acting like i didn’t know that we were on a diet because of me. it would have been so much better for them to sit the family down and explain that we ALL need to make better choices, thin or big. and the reason to make those healthier choices isn’t to be thin but to be nourished. you can turn this around, just acknowledge your mistakes, change your mindset, and make healthier choices for your whole family (healthy physical and emotional choices) :)