Unfortunately many doctors are just assholes about weight, and feel that as a doctor it's their duty to chide any fat person about their weight regardless of their specialty or what the patient came in to have treated. I've had that kind of intrusiveness from dentists!

My my experiences have been fine at the Davis Square Harvard Vanguard office. I disliked one doctor (who grabbed my contacts out of my eyes without giving me a chance to be prepared or to take them out myself), but he's no longer there.