How do I go about asking my wife to slim down and do a little makeover?

My wife used to be one hot mama. Now that we've been together a while (no kids) she has started to let herself go. She's put on some weight, especially in the face, and doesn't do much with her hair or face anymore. I was telling my dad its like having a sewer rat gnawing on me instead of having an exquisite sexual encounter any more. He said my mom was the same way but he never had the courage to say anything. Next think he knew, she was wearing denim shirts with roosters and snowmen on them. My wife better not get that far out there! So how do I go about asking her to get back into the game of taking care of herself? I am not calling the kettle fat here. I am 5'9", 150 lbs, in good shape. I exercise somewhat regularly and manetane a good diet. I know I could ask her to come with me on my runs but I know she wont. She uses that time to 'self-sex' herself because her sex drive is more than I can handle. We usually have sex at least 3 times a week but she wants it multiple times a day. At least she is always eager when the time comes. Thats probably the only way its worth it for me anymore cause she has gotten overweight a bit and doesnt trim like she used to. Trust me, its not great when the area above your penis gets rug burn from your wife's ****** which grows random hairs like one of those moving pipe screen savers.