Gaming isn't something that leads to unhealthy habits, but it's definately something that can influence them if done the wrong way. Up until recently, there hasn't been a whole lot of influence for gamers to do anything other than game. I think the Wii was the first big step in that area that hit home with people, and yes a lot of people argue that they sit down playing interactive games, but even if one person actively plays it then they hit their mark in designing it. You are never going to be able to apply a fix to society that makes anyone and everyone do a specific act. Too many people are hellbent on acting on their "rights" and making sure their voice is heard. Yes you have a voice and it matters, but it doesn't mean you have to express your opinions all day every day. On a side note, Facebook is become such a interesting site since it's inception. When I joined facebook in 2005, you needed a college email to even make a account. I kinda wish they had stuck to this. People spend way too much time trying to make themselves look like something they aren't. I really got off track here so I apologize and I'll try and get to my point.
Today, there is a lot more incentive to get in better shape. I've watched a lot of famous streamers and you tubers go through physical changes and actually roll that into more sponsorships. I think this is really cool, but at the same time I hate that it makes some people ashamed of having people view them. I'm a big boy and I'll admit I used to be very shy about showing my face on camera. I used to barely even voice chat because I was so shy. Regardless of how you look, I think there are habits you should form when trying to be a healthy gamer. Like all things in life, if you enjoy it you'll want to do it more. Enable yourself to continue doing it by staying healthy and making good uses of your time.
Eating can be a big problem because you are usually so involved in your game that you end up eating while playing. Anyone that has picked Doritos cheese out of their controller can relate to this, and it's gross and unnecessary. We live in a world where physical interaction is so limited but I advise you to take time not eat and have a conversation with someone, and talk about something other than games. Sodas can be bad as we'll. you go for a dew and before you know it the whole 12 pack is empty. Sodas aren't going to help you in any way other than caffeine, and even then it's a bad way to keep your body awake. Try and mix it up and drink a water in between or something that won't dehydrate you and keep you in and out of the bathroom every hour.
In a lot of games we play there are loading screens. If your like me, you've probably memorized them all because you see them so often. You should try and do something active during that time, and I don't mean google game info. Do some push-ups, doing some exercise, or even clean up the house a little just to keep yourself active in the downtime.
Third and finally I'd suggest getting actual rest and sleep. I know we all love gaming marathons but regardless your body needs it's rest. Even if you can go long periods without resting, it doesn't mean it's a good thing. Also, if your married like me, your wife or husband would much rather you go to bed with them instead of hearing you try and beat a boss while they go to sleep alone. And trust me, I'm speaking from experience on this one.