I feel awful for this

So my bf and I have been together for years and when we met he was very fit and in shape, as was I. Over the years he has gained about 4 stone and is now in the overweight category and none of his clothes fit anymore, obviously I still love him but it annoys me. NOT that he gained weight but because he constantly complains about his weight but does nothing to change it. He always says he’ll start a diet or exercise “next week” and never actually does, the weight is piling on and it effects his physical life and even our sex life. He continues to eat unhealthy food and it’s to the point I’m starting to worry about his health but he still doesn’t eat healthy or do anything. I don’t want to seem awful and pushy but I just want him to be healthy and happy which he clearly isn’t if he keeps complaining about it, any advice?