Getting the spouse involved?

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My husband's doctor always tells him he needs to lose weight. He's in danger of diabetes. Also, his liver enzymes are high which causes him pain sometimes. Every once in a while, he'll get really motivated and work out, but that never lasts more than 2 or 3 days. He works on his feet 12 hours per day so he's usually tired when he gets home. I'm the one who makes dinner and I try to keep it on the healthy side, but since he's gone from 7am-7pm I don't really know what he's eating for breakfast and lunch (he doesn't like to take a lunch with him because it's free at work.)
I just don't know what to do to make him more motivated. He's a little sensitive about his weight, and I know I would be offended if he said something to me about mine, so I really need advice about how to help him gently. And he's totally against getting an account on here because he thinks he'll become "obsessed." Advice please??