Thin privilege is being able to fit into an MRI machine comfortably and get scanned whenever necessary.

Someone I know went to the doctor for an MRI, having told them twenty times on the phone that the machine would be too small, and having them insist “no one could be that big” and that it would be fine; she would fit. Feeling alright, said person arrived for the MRI, and they literally taped her arms and legs together to make it easier to stuff her into the machine. Like she said, she was too big for the machine, and apparently she exceeded their expectations (even though those machines are uncomfortable for a person of any size).

Thin privilege is having medical equipment suited to your size.