From a man to a woman if i told you. "losing weight will help you feel better and increase your attractiveness to the opposite sex"
what would be your response? and an honest one, not the "i'm gonna lie to prove my point response"
Honestly, I would probably be defensive, and say what I TRY to do (honestly) to keep myself in shape. You have to give me a personal reference and make it meaningful to me, not just state something in absolutes. A better way of going about it would be to say, "Why don't WE go out walking this afternoon after Sunday dinner? It makes ME feel good to do that, and I want to share that with you? or, "I want to help you with (fill in the blank) because I know you've want to keep up (fill in the blank)."
Some other women would probably get pissed off and have a good return to your statement, such as, "other men don't seem to mind my weight," or, "I already feel good about myself."