Background: The natural history of patient weight while on surgical waiting lists of 3 months or more has not been previously reported. Methods: Data was obtained for adult patients undergoing surgery with category C (more than 3 months) and D (patient not yet ready) bookings for elective surgery in one local health district in New South Wales, Australia, over one calendar year. Booking dates, surgery dates, booking category, name of operation, and weight recorded at both booking of surgery and performance of surgery were extracted from the electronic medical record system. Weight changes of m...