Well said Marnie.
If a thyroid problem causes obesity then that person needs are special. Many other handicaps require special services or products and this should be recognized as a handicap also. Does a blind person's seeing eye dog require a ticket? I don't know. Does a caregiver who escorts an elderly or mentally handicapped person along on the trip require a ticket? Well, of course. Because the caregiver is taking up a seat. Even though the handicap requires a caregiver to go along. If a handicapped obese person requires two seats, then it should be paid for.