As far as a solution, one I have used with a few close friends (After either offering to help or showing them the way) is:
I refuse to talk about or listen to you complain about something you can do something about. Change it or just drop it. The energy you spend complaining about it could be better used changing it.
Spouses and significant others especially feel entitled to complain ad nauseum. One of the very cool agreements my ex and I had was, after the 3 time, we reminded the other--"Okay, that's the third complaint--what are you going to do about it?" It was a gentle, pointed reminder to shut up and DO.
After you're settled, spouses often seem to want you less desirable to others (heavier, etc) as a way of feeling more secure. In my mind, the expectation should be that we maintain, to the extent possible, the great body (among other attributes) that first caught our attention.
Multiple kids and double digit marriage years are not excuses for 50+ pounds between a couple. People have time for what they want to have time for. Period.
Complication makes it easy to explain failure.