I'm so sorry that your family members have treated you with disrespect. My mom made a few comments when I was young about losing weight, although I was only maybe 15 pounds overweight, nonetheless it makes you feel less than.
I have 2 adult children and to be honest I have worried about their weight. Neither is overweight, but I know the challenges I have faced and don't want them to ever go through that themselves. However, I would never comment negatively to either one. My so is a body builder, and that has worries, and my daughter has always been small. Maybe your family cares but has a shi*** way of showing.
Anyway, do what is best for you and do not feel guilty not telling anyone. I have a lot to lose & really don't care who knows, but we all need to do what is best for our own self.
Best of luck on your journey!😊