Pretty much every doctor is biased, some are aware of that bias and try to actively work against it and others just seem to be completely ignorant of it. Doctors do incredible work, but at the end of the day, they're still people who live in the same biased world that we live in, so it's only natural that they carry their biases into their work. Just like any other profession. It's also not just bias against fat people. Underweight people also often struggle to get a doctor to take them seriously, as well as people of different cultures and ethnicities, or women. We don't live in an unbiased world so it's really naive to think that doctors are somehow above this. Also, not everyone has the time or the resources to visit doctor after doctor until they find someone who might actually take them seriously. None of us were at Carrie's appointment, maybe it didn't happen the way she told it, but it's weird to dismiss it because you think doctors always know best and can never be wrong or biased.