I have a bit of a strange situation- I had issues with digestion for about three years (probably a combination of an ulcer and stress). At any rate, I changed my diet fairly radically, and went from about 180 to 160 (too much weight loss as I'm 6'2").
Around Christmas, I was feeling mostly better and said to heck with it, I'm going to go back to eating normal things and see what happens. Turns out I could without too much discomfort, and gained it all back and then some (188) by March. While I'm glad that I was able to gain back to a more normal weight, the adjustments I've made (back to the treadmill and cutting back on some of the things I'm eating) haven't got my metabolism back to where it was.