I've definitely gained post-adoptive baby weight, but only once my son hit toddlerhood. When he first arrived, the change in our lives, lack of sleep, and lack of time kept us from eating...and we lost some weight. But, once ds started eating solid foods, that was it. Now I find myself eating things he doesn't finish or eating the same things he does out of convenience...not a good habit.
It really is a a pain to fix two different meals, though. Let's face it, grilled cheese and baked chicken nuggets may be okay for toddlers, but play havoc on adult waistlines.