I did it a couple of times, or more precisely a couple of times I let my eating desires out from their usual restraint, gained ten pounds in about six weeks, and realized that I wasn't ready for the consequences of totally cutting loose.
I went from 170 - 180 when first in university, and I did manage to lose it again....but that six week gain took me two years to get rid of.
Nearly a decade later, I'd gotten up to 200 a year after getting married, and while my wife was away on a work placement I cut loose, and hit 210 in (at most) six weeks. I never really lost that weight (did get down a few pounds below it a couple of time, but have mostly been over it by 5-15 pounds).
Both times I was happy with the gain, just not willing to make the associated life changes required to really indulge my gaining side. I know that those experiments didn't help in everyday life, but really no regrets. I need those occasional indulgences to keep myself sane-ish