These problems have nothing to do with night shifts or the people that work them. Having worked a couple of 12 hour night shifts in my work history. I found that there are a couple of easy answers to these dilemmas. Prioritize your health! Don't drink soda. If you need a boost, those stupid 5 hour energies work just fine on a consistent basis. EAT FEWER CALORIES! A nice grilled chicken breast, and a piece of fruit for your first break,the same with something with a few carbs in it during your lunch, and a grilled chicken breast (season as you will) w/ a piece of a different fruit. during your last break. Drink lots of water...iced if possible.
GO TO THE GYM AFTER YOU GET OUT OF WORK! You don't have to be there long, or do it all in one visit. At least 45 minutes of cardio ( I break it up into 3 15 minute cardio sessions on 3 different machines) , 3 sets minimum of 20 reps for abs (any exercise, as long as it is like a partial or full sit-up) and maybe 2 or 3 muscle groups (shoulders, lats, pecs, bis, tris, quads, hamstrings, calves) a day. Do this 4 days (or more) a week and in 4 months you will look awesome! Also for guys....gyms in the early AM are filled with cougars and other single women...lots of opportunity, just remember that you are really only at the gym for yourself. Ladies, the better you look the more we want to look at you...admit it it is just the same the other way around.
Also for men and women, there tends to be a strong differential between the attractiveness of someone who takes really good care of their body, and someone who does not....Case Closed.
Oh, and one last thing. Don't try to live like people who are not on the same schedule as you. Nothing causes more stress than bouncing back and forth from normal hours to night shift hours.