Nights can be a huge shock to the system. Too easy to get shit food since anything open late is usually fast food or pizza, and really hard to motivate yourself into getting up for the gym since you always feel tired. I've been on nights for a few years and fell into that trap but was able to get things moving in the right direction. Crockpot meals are my go to now, easy to prep and cooks while you sleep then bam, meals for the whole shift. Foiling my windows/blackout curtains helped block every ounce of light to maximize sleep, and the rest is just finding that drive to get up and do something. Doesn't have to be much, every minute you're physically active is a minute more than what you would have done before. It all adds up into some big-time life changes, the most important thing is to just start no matter how small that first step is. Good luck!