NP here, maybe a couple things to add.
1) Blindfold idea is interesting, but turning off the lights also gets that job done.
2) I've always been attracted to my DH; he has aged beautifully, he's just exactly the physically perfect match for me, both in face and body. Can't get enough of looking at him. And even though I'm "attracted" to him, over the years it's been harder to translate that into sexual desire, partly because I'm older and the drive has decreased, and partly because holy cow, it's the same guy for 17 years now! So my point is, it's possible that some of what you are attributing to his weight gain could be just the regular doldrums of a long term relationship.
3) Ok I know you haven't been totally direct with your DH, but go with me on this for a moment because you have tried through other means to get him to lose weight.
I also think often for women, if a guy doesn't take their feedback (say about Thing A), they can often feel like the guy's lack of taking the feedback is symbolic that the guy doesn't care what they think. Then the turn off isn't just about Thing A, but becomes also about Thing B--"he knows, but doesn't change, therefore doesn't care enough about me to do something about it." Or, "He won't fix Thing A because his job is too time-consuming, so, I come lower in the hierarchy than his job," etc. Which for many women is a huge turn off.
So is it just Thing A, OP (the weight) or is it also Thing B (your feelings because he won't lose weight)
I think it's important to realize that if a DH doesn't fix Thing A after you told him how Thing A impacts you, it may not be because he doesn't care, or chooses work instead of your feedback, etc. Thing A might be something bigger for him.
4) So in this situation, Thing A is the excess weight. Many people don't lose the weight for bigger reasons than "they don't care about their health, or they prioritize their health lower than their job," and all that. Many people don't lose weight because, for example, they are afraid that if they DID lose the weight, what would it mean if their spouse was still unattracted to them? Or if they are single, if they STILL couldn't get a boyfriend/girlfriend? The fear is, they might have to deal with the concept that they are unlovable, or undesirable.
Or, less intense...they don't lose the weight because they are deeply engrained to eat to deal with stress, and they haven't figured out a substitute.
Anyways, just pointing this out, OP, because it might not be so straightforward for you (and it also might not be so straightforward for your DH.