When I got my snake 2 months ago he had been fed nothing but pinkie mice, once a week, his whole like (approximately 6 months) and was underweight. I switched to small mice, and fed him every 5 days for one month. He plumped up quite a bit during that month, but still had a pretty prominent spine. For the past month I've been feeding him large mice every 5 day, and he's finally starting to get nice and round.