My husband is the same way.
I really dont care about his weight from an appearance aspect but I DO from a health perspective. People die in their 40's and 50's from heart attacks and other "I didnt eat right and exercise" type of problems." I dont want my children to lose their father while they are in elementary or middle school.
What has started getting his attention is his parents. They are both overweight and have poor eating habits and no concern at all about trying to eat healthy. In the past two years, they have had A LOT of health issues and been hospilized on and off. They cant do fun things with us like go to the zoo, or even to a playground because it is too much walking - these are things that most people their age, or older, who have kept in shape can do. Their quality of life is suffering greatly because they wont even attempt to exercise. Note: They are NOT grotesquely overweight - they are regular looking overweight and do not exercise.
Continue to bring healthy food into the house - make sure that half of the dinner plate is covered with vegatables. Continue to ask him to come to the gym with you - as a favor to you. Make a swap - you will take over his garbage duty if he will come to the gym with you.
If the opportunity arises, tell him how important it is to you that he is healthy and models a healthy lifestyle for the kids.
We go for evening walks - the whole family - and its a chance to talk and relax without a tv or cell phone to distract someone.
I also plan family activites on weekends that involve walking, swimming, hiking...
I also beg him not to buy soda or ice cream or other sweets because it messes ME up and he is really good about that.
It doesnt achieve the level of fitness that regular gym work outs would, but it does achieve the goal of keeping a healthy life style front and center.