I'd been married for about 22 years, DH growing bigger each year. He generally did the grocery shopping, and neither of us was big on planning dinners. I was in a work out habit since about 2004 (I can tell you the date I first joined a gym!), and have tried to keep an eye on my calories, but I was alone in that game.
I got pressure from my family, who believe that a wife should be able to control her husband's eating.
In fall of 2008 some switch in his brain flipped (he had some difficult medical news, and obesity was the first thing to treat), and he got with the program, our food at home changed overnight, our planning got good, and his health improved in every way, and my family and I are getting along much better!
So, my take home lesson is, you can't cause these changes in anyone else, you can provide support when they are ready.