Dear Carolyn: My husband and I have both gained significant weight since we've been married, but I'm trying to mitigate that with diet and exercise. He isn't, and every time I try to talk about it, he makes me feel like the bad guy for bringing it up.

Look, we're both approaching 40, and I know we'll never be the "twinks" we were when we met, but I'd like to be better than I am, and I am finding it very difficult to get healthy without his support.

He's prediabetic. He has sleep apnea. His sex drive is nowhere near what it was when we met. And it's frustrating because all of this is correctable and he's refusing to even try. It's like he doesn't care.

I love my husband. I will never "fat-shame" him, and I know my weight struggles aren't his issue. But I would find it a lot easier to tackle this if he were more supportive, and if he would try to be healthier, too. I don't know what to do, short of giving him an ultimatum: It's me or the sugar, dude.

Carolyn says: I wouldn't do that — not unless you're ready to lose.

Not because he likes sugar better or because you're not somehow worth it to him, but because food is a formidable opponent that fights dirty.

For one, you two can't just banish food from your lives and start over; you can't move away from it or spend time only with friends who abstain from it. You're in its presence at least two or three times a day as you fight it, and the rest of the time it's calling to you from the kitchen. A lot of it is engineered to tempt or outright addict you.

And, our bodies are wired to hold onto fat harder whenever we try to get rid of it. And poor nutrition and inactivity can lead toward depression, which can lead to poor nutrition and inactivity.

So consider that even as you feel overmatched without his support, you're much further along emotionally than he is: You've made the decision to tackle this, and are making difficult changes.

He's just not there yet and won't get there on borrowed motivation; he needs his own. A lot of it. Anything he does in response to an ultimatum won't really be his.

It's not hopeless, necessarily. It's just that, if he does change, it's going to be on his schedule, for his reasons.

This also doesn't mean you can't speak up. He deserves to know what his life partner sees in and feels about him, and what his inertia may ultimately cost him — none of which counts as fat-shaming. It's life-alerting. If you haven't yet been honest with him, then tell him kindly: You mourn the loss of his sex drive, and struggle deeply with watching a pillar of your life self-destruct.

You can also ask him how he wants you to handle your concern hereafter. This is an underrated step. You've interpreted his preference from his defensiveness, but that's not the same as knowing what he wants you to say or not say. Plus, asking him forces him to think about what he wants — not just from you, but from himself.

From now on, too, you can ask him to join you on walks, whenever you go. Take yes or no for an answer without reacting.

Most important, once you've made these points and asked your questions, stop talking about it — and quietly keep doing everything you can "to be better than I am." A sustained effort is tougher without his support, yes, but it's your best argument to win that support.

E-mail Carolyn Hax at tellme@washpost.com.