I don't think it's as much physical attractiveness as it is the way the patient presents themselves and their attitude. I could care less what size you are or what you look like, it's your overall demeanor.
But if Patient A, who is young, blonde, and weighs 120 comes in smelling like a thousand camels, didn't bother to put on pants before she called the ambulance for her lower abdominal pain that she's had for six months, and is yelling at me to get her a dinner tray before I even triage her...you bet I don't want to spend anymore time with her than I have to.
I'd rather take care of the elderly man who weighs 350 pounds and is incontinent that comes in for fever because he and his family are polite, have a legitimate health concern, and are grateful for my care.
But I do think some people treat well-dressed people better, and I have a theory why, at least in the ER. The ED in my city, at least, is used as a primary care clinic for people that don't have insurance. So if someone comes in who is well-dressed, people assume they have insurance, and if they are at the ER, they must have a real emergency that their PMD couldn't take care of in the office. Is it right? No, but it happens.