Compassion is supposed to be a hallmark trait of the medical profession. Any doctor who lets his personal beliefs get in the way of his practicing medicine in the best possible way to ANY patient - be s/he fat, thin, muslim, atheist, black, green, prisoner, retarded, or just an average joe - is a bad doctor. If a patient is obese then yes, it poses a serious health risk and a problem. My job as a doctor is not to lecture that patient or make fun of them, but to try to help them as much as I can with the tools I have at my disposal. The same for alcoholics, drug addicts, and anyone else. Because at the end of the day said behavior is usually just a symptom of a different, underlying problem.