Video game addiction

My SO is obsessed with playing video games with his friends. He will stay up until 5 or 6am with them just gaming, and it's making him extremely tired and want to spend less time with me and outside in general. I know lots of guys have addictions with games/porn/lots of other things- is there something I can say that will get through to him? He doesn't like it when I bring it up because he feels like I'm bossing him around. How do I get through to him that it's not healthy for him and it's bad for our relationship??