For love and obesity
Scientists are discovering trends already known by every girl who's ever lived with a man. It seems that marriage and cohabitation are enough to push ladies, and for a few years their partners, into gaining weight.
Researchers aren't sure what the cause is, but I'm willing to guess it's the men's eating habits (they do, after all, eat like men), combined with a change in lifestyle. All of a sudden it gets a lot harder to make it to the gym when you're dating someone. A significant other can zap free time faster than a second job.
To borrow (and mutilate) a line from a great song, we're like babies and cats, when we are happy we both get fat.