weight?????

How do you tell your fiancé he has gained a lot of weight and you are worried about him? We both have gained weight since the beginning of the relationship, but I'm working on loosing mine he just gets frustrated trying his old clothes on and gets upset. I hate seeing him feel like that because that's how I feel but I'm doing something about it! He isn't!!!! I just want him healthy and live a very long time. We are getting married next year and want to start a family.