I can see that you care a lot for your friends' well-being and happiness, and are concerned their lifestyle might be harmful for them long term. Instead of going straight into talking with them, you're getting more information so you can do it right. That's very considerate of you and I'm really happy they have such a good friend. Seriously, your friends are lucky to have you.

Bringing up concerns with anyone, especially those close to you, can easily lead to hurt or conflict if the other person misunderstands your motivations and feels misunderstood, criticized, or judged. I want you to succeed if you decide to talk with them because I can see you only want to ensure they can have healthy, fulfilling lives and I'm sure you want them to see the same.

Have you considered looking into any literature on brushing up on communication skills for difficult conversations? If you're open to it, I highly recommend Nonviolent Communication by Marshall Rosenberg. It teaches how to identify and express core motivations and the feelings behind them, learn the same when others speak (even if they aren't initially aware themselves), and work together to address everyone's needs.

Disclaimer: I just used the bog standard Nonviolent Communication method in this comment. Old me would have said something like "you're judging your friends and are gonna piss them off" while having the same core feelings and motivations I felt when I wrote the main comment. NVC helps me figure out my needs and feelings as well as yours, then talk about them without sounding like a judgmental, overly critical douchebag.