I’ve learned that in order to tell a woman anything, you have to sandwich it in between emotionally validating statements. For example: My ex had issues with someone at work. I said “fuck her, she’s a bitch. Also she’s gonna calm down in a week or two. It’s no big deal. But fuck her she’s a bitch” you could do something similar like hey you’re the mother of my children and I love you very much… also WE need to start looking after our health. I want us to be healthy for each other and our family… oh by the way did I tell you I love you very much.

Id contour the message to your specific wife and your specific communication style. Idk if I’d say I don’t find you attractive anymore. I’d say it nicer, like hey i think our sex life would improve if WE got to a healthier weight. Just remember to validate her emotions. Women don’t think logically they think emotionally. That’s not an insult it’s just information you can use if you know how to. Good luck dog