Diet
Keep healthy snacks on hand at your desk at all times. Foods such as veggies, nuts, and even granola bars are better than the alternatives. If you don't snack on healthy foods throughout the day you're more likely to indulge in a huge, heavy lunch or the desserts a coworker brought in.
Learn to meal prep and make large amounts of your favorite healthy dishes to bring in for lunch and snacks each day. Making your own food is the best way to know what is going into your body and to avoid binge eating junk at lunch. Plus it helps save you money!
Water
It is really easy to get distracted at work, especially if you sit at a desk all day. You could easily forget to get up and grab water frequently enough. Water is the most important thing you put into your body. An easy way to know you're getting enough water is to aim to drink half of your weight (pounds) in ounces of water (so if you weigh 150lbs, you should try to drink 75oz of water every day). Consider buying a large 30oz Yeti or similar tumbler. Finish the tumbler 3+ times a day and you know you are on the right track!
It is also a good idea to try to ditch the sugary drinks. Try iced tea instead of soda or Gatorade. And a big bonus is to stop adding sugar to your coffee and limiting creamer.
Take Breaks
Sometimes you may feel like you should power your work to finish everything "faster," but there are consequences. Skipping those breaks can leave your brain lethargic and your work sloppy. If you stare at a computer screen and sit at a desk all day, taking breaks is mandatory for better health. Not only will frequent breaks keep you more alert, but it is also better for eye health and your work will turn out stronger in the end. You will be more productive and come across more clearly. Take a lap around the office or a step outside every 60-90 minutes if you can.
Posture
Keeping proper posture is not only a good tip on how to stay fit working a desk job, but it also makes you look better. You will appear more in control and even more attractive when you keep proper posture versus sitting slouched over. Keeping correct posture is a conscious effort though so try to make a habit of thinking about it or even setting little reminders on your computer.
Wipe down workstation
Keep sanitizing wipes on hand to wipe down your workstation and take a couple minutes at the end of each day to reorganize your workstation. Nothing is better than walking into a tidy area every day!
Stress Management
Mental health is just as important as your physical health. Life is full of stress and it is totally normal to feel it. How you handle it is very important though. Try to incorporate things you enjoy such as spending time with your friends and family. Indulge in a massage after a good workout at the gym or buy a new outfit because you know you've been eating right.
If life and work are becoming too much, consider asking for a personal day or even flexible hours until you can get your head back in the right place to focus on work full time.
Buy an adjustable sit to stand desk
These are great.
Deskercise!
Consider downloading an app like Workout Alerts to remind you to get up and move every once and a while.
Take the stairs.
Walk around the block on your breaks.
Shake your legs and tap your feet at your desk, moving is moving!
Step outside and hold a wall sit instead of taking a seat on the bench.
Do some calf raises or squats while your lunch heats up in the microwave.
Squeeze your butt for 5-10 second intervals while sitting at your desk.
Do tricep dips on the edge of your desk everytime you get up.
Waiting around in the hall for someone? Do some pushups against the wall.
Use your arms to push against your armrests and lift yourself off of the chair for a few seconds.
Grab the edge of your desk while seated in a swivel chair. Lift your feet slightly off the ground and use your core to rotate yourself back and forth.
Squeeze your ab muscles and hold for 10-15 seconds. Repeat throughout the day.
If you own your business, consider investing in a company gym membership (complete tax write off too!) or asking your boss if they would consider a gym program. It could even cut costs on your insurance. It could even turn into weekly or monthly fitness challenges between the office employees.
