Yep, twice, actually (as in, for more than 'just' 1-2 lbs).
First time was when I went to college at 18. Everybody talks about the freshman 10 or 15, for me it was actually the reverse process. The second time was in 2008-2009, when I prepared for the CAPES
concours (teacher competitive exam); one of my resolutions was "I won't be on a diet this year, because I need to focus my mental resources on something else than counting calories", and now with hindsight, I bet that had I actively tried to lose weight, I'd probably have gained instead, or not budged at the best.
Both times, it didn't happen in an unhealthy manner, I must add. I ate in quite a balanced way, I even crammed in fencing classes (12 years ago) and jogging (this past year). But I think the main component of this weight-loss-without-doing-anything was that I was seriously busy with intellectual work: both times, I prepared for a national competitive exam. I have a tendency to munch and graze only when my hands are not busy, for instance when watching TV, and so, it just doesn't happen at all when I'm spending most of my time buried in books. And preparing for those
concours is something else than 'only' preparing for a License degree, because you can't just focus on getting an average note, you have to make sure you'll do better than everyone else on top of it. So I was focused on that, had very little time to spare, and wasn't tempted to eat some more after lunch or dinner, because I had to hurry and finish my homework for the day, not waste time diving into a box of cookies. (Honest.)
In fact, I tried to munch on stuff while working, early in September. I ended up putting chocolate on my copy of
Jane Eyre. It angered me, seeing my poor book that way, and I gave up on the eating chocolate part.
