a) does obesity affect your interview success
No idea. It's not like we have any controlled trials where people apply to med school twice, once while obese and a second time while svelte. But as others have already pointed out, as a society, we do have a bias against ugly people, and obesity is considered ugly by the majority of people in this society. So it's certainly possible.
b) does it affect your med school success.
My guess is that it has very little effect on the first two years, where you're basically being evaluated by how well you memorize material. On the wards....well, again, same as above.
Her fear is that someone would ask her about it in the interview
I think this is unlikely. At any rate, I've never heard of it happening.
or that instructors would look at her differently
Well, physicians are party to the same biases as anyone else, so sure, this is entirely possible. There's a second source of prejudice against the obese that is particular to health care providers though, because morbidly obese patients tend to be among the least desirable patients to care for. Any unpleasant procedure (ex. pelvic exams, inserting a urinary catheter, rectal exam, etc.) is doubly unpleasant when you have to perform it on a patient who is morbidly obese. Even relatively "easy" procedures like phlebotomy or eliciting deep tendon reflexes can become a difficult task if the patient is obese enough. My experience is that it's very common for health care providers (nurses as well as physicians) to feel a little dismayed by walking into a room and seeing an extremely obese patient sitting in there. It's just harder all around to care for them.
Another observation this student made rang very true in my experience: there were practically no fat people besides her in her med school class. In my class, the biggest person is about a size 16, and she stands out.
I think there is quite a bit of self-selection going on here though. You don't see many morbidly obese applicants, either.
Premeds tend to be more similar to one another than they are different in many ways besides their weight. I mean, there aren't very many med students who are in wheel chairs, even though, unlike the obese, it is illegal for the adcom to discriminate against them if they are capable of performing their duties with reasonable accommodations. But the reason we have so few med students in wheel chairs is because so few applicants in wheel chairs apply, not because we're discriminating against them.
It's not exactly fair, but program directors and admissions committees have a strong stake in filling slots with applicants with the greatest chance for success. There are so many applicants these days with good GPA/MCAT/EC's that these marginal issues have to be considered (insert arguments here on the effect of being a married woman of child-bearing age and it's effect on the match process.)
I'm not saying it couldn't happen, but I've been a student adcom for three years now, and I have never heard of an adcom not wanting to admit an applicant because the applicant was obese, even with the obese not being a legally protected group. Interestingly, at one meeting there *was* an adcom who expressed reservations about admitting a candidate with a PhD because they felt this candidate might have trouble fitting in with the younger applicants. Naturally, this view was not terribly popular with yours truly.
