In high school and college, I played lots of sports (tennis mostly), so staying active wasn't a problem, as I got tons of exercise compared to the average person.
I am a year and a half out of college now, and the white collar lifestyle makes it a lot harder to stay in shape. Before covid when I was in the office, people would constantly bring in soft pretzels, cookies, pizza etc and how can you resist eating that when you are bored at work and staring at it all day. Additionally, it is a lot harder to be motivated to go work out or play a sport when you get home at 6 after a long day of work and a crappy nearly hour commute. Here are some of the ways I try to stay healthy
I drink lots of water, and only water. Only other thing I will drink is occasionally alchohol, or like once every 3 months I have a lemonade or gatoraid.
The past few weeks I have tried to stop allowing myself to eat after dinner. I generally eat decently during the day, but the after dinner video game time usually turns into snack time for me, and it helps me cut down on calories in general but moreso crap food
Cut down on sugary foods - Sugar is absolutely addicting, but in my opinion it's like the worst thing you can have (check how much sugar is in a serving of soda). While I still will eat desserts, I am trying to have them less frequently (only when offered at a party or whatever, instead of always seeking out cookies when chilling at home)
Play sports like tennis or pickleball - running just to run is the absolute worst, it is so boring and I hate it. The only way I can consistently stay in shape in playing sports. This is much easier now during the summer, but was more of a struggle during the winter.
I hate most vegetables, but need to eat more. This is a work in progress. I hate how asparagus makes your pee smell.