I'd imagine any sedentary job has the potential to make you gain weight. I've been a reference librarian for 16+ years: I spend a good part of my day parked on my ass in front of a computer. I consider myself in average shape and try to exercise/eat right and all that good stuff. I've put on a few over the years but I think I've lost a bit recently as my pants are getting looser (I stopped drinking soda back in April).
Anyway, since library work isn't a male dominated profession, I work with a variety of gals of all ages and sizes. I've enjoyed watching one gal, with a figure similar to "Plump Princess" (tall, leggy, pear-shaped), go up and down in size over the years. She's also broken two office chairs (that I know of) this year alone.
The teenagers we hire tend to be skinny when they start working there, stay through their college years and some of them fill out and some don't.
Dennis