I came back from a knee injury and Europe 13 lbs heavier. And I couldn't really get rid of it, even though I was working out and playing racquetball a few times a week. The diet change was what did it for me.
I went from this, which was taken in Italy:
To this, which took about 16 days. (It's amazing what good nutrition can do...)
Things definitely slowed down as far as my metabolism goes. (I'm 38) But I connected with a good nutrition system and it's been awesome so far.