I agree with others; it's not about having high standards but having a double standard. If you want to date someone who is physically healthy, then why not put effort into getting physically healthy yourself. This is more than just appearance-- it is about health, self-care, motivation, etc. If you feel it is impossible to move towards becoming a healthy weight (absent a serious medical condition that is causing the obesity), then perhaps THAT is the issue to work on, probably through therapy. If you don't make the effort to take care of yourself, others will notice that and be less interested-- not because of the physical, but because of what it says about the person's own unhappiness/struggles inside.

I know that, for me personally, being healthy and surrounding myself with others who are healthy is important to me. I don't care if my partner is a size 2 or a size 10, but I do care that she chooses to eat healthy foods, exercise, not smoke, etc because that tells me she has good self-care and wants to be around to be there for me, her daughter, etc.