Although its not 100% true, I think if it was me, I might say that in order for you to achieve your goals, you need his help, ie you would love him to be your exercise partner, you cant have him eating junk or drinking because it makes it difficult for YOU to stay motivated and on track.... That way, no hurt feelings, and you both get the benefits... I would think that he would be happy to help you out?
I suppose if not, then just honestly come out and say that you are a little concerned for his health. I wish I had done that for my dad sooner. He smoked 60 cigarettes a day, ate junk, (was about 25kgs overweight) and did no exercise at all. He had a heart attack at 38. Thank god he was ok, but I wish I had of offered that support BEFORE something like that happened. (he has now lost 20kgs, walks daily, and although he hasnt stopped
he has cut down substantially on smokes) Just say that you are concerned, because you love him, and you dont want to lose him.... good luck with it hun! xx