I work 5 12 hour shifts every week. I have back issues and nerve issues with my feet. On average, I am sitting at my desk 10.5 hours a day. I have customized my chair with both lumbar bloster and a cushion to help with sciatica.
That said, I get up at least once an hour and make a "lap". 1000 or so steps helps get everything moving, and gives the 👀 a break.
Since I started this job 3 years ago, I am DOWN 50#