You may not know this, but humans are not meant to sit around all day. A lot of people don't realize that evolution doesn't just happen over the course of a few thousand years. Evolution takes hundreds of thousands even millions of years to happen. What does that mean for humans and sitting? Well we shouldn't sit around for 12 plus hours a day. We have not been living with our current technology long enough for it to have affected the way our bodies function. Human beings were hunter-gatherers, which means that we spent most of our time on our feet. The only times humans were really just sitting around was when they were eating or going to sleep.
Our metabolism is still adjusting to the conveniences that we have now a days and that means they are causing our metabolisms to slow down drastically. No that doesn't mean that you should spend the entire day on your feet, that's not possible and it's also harmful. However, you should stand up throughout the day. Thankfully in my office we all have sit to stand stations, so I will usually stand for about 1 hr in the morning, then sit. I alternate not based on a schedule but based on how my body talks to me. While you're at work, try to pay special attention to when you start to feel weary, tired, or have leg/back pains. If you can, step away from your desk, go for a walk or even work while standing up. Your body and your waistline will thank you for it!