Another vote for leading by example.
DH & I both wanted to lose weight earlier this year, and I've made it further along the weight loss path then he has, mainly because I've had more opportunity and motivation to change my diet and exercise levels. He's still working on his diet, as am I, but we both need to start moving more and find the motivation we had in the first place.
Both of us enjoy eating out a bit too much and vegging on the couch, so I just have to remind myself that I like my new look a lot better then my old one, and I like the way I feel now quite a bit more.

And that inspires me to get off my bootie and get moving! I hope it will gradually push him in the right direction, but it will have to be in his own time.