I prefer to stand mostly because it helps some mobility issues I've noticed while doing olympic weightlifting, notably, sitting for long periods really tightens

I prefer to stand mostly because it helps some mobility issues I've noticed while doing olympic weightlifting, notably, sitting for long periods really tightens my hip flexors and external shoulder rotation. It's taken me a couple of years, but gradually my overhead squat has become stable and low. But that process wasn't due to me just standing: over these years I've also done lots of exercises to explicitly improve the position. Standing all day vs sitting all day is just something I notice when I get to the gym. After a long day of meetings, I find I need a solid 2-3 more minutes of hip flexor and shoulder work to get things moving. However, I don't think for a second that standing all day has anywhere near as significant an impact as doing olympic weightlifting 4-ish hours a week. Building up the body's ability to handle high intensity physical activity doesn't take long, but over the long term, you can make major improvements. For me, I've easily more than doubled maximal intensities I can perform: I recall a time starting out that a 225 lb deadlift was difficult. I regularly pull 400-450 pounds now, and can do it for multiple reps in a single session without significant soreness the day after. And notably, I started at the age of 36, and my bodyweight hasn't changed that much, though I'm less pudgy and a little more muscular. I'm hardly what someone would spot as a "beast" or associate with being a bodybuilder. (Lifting for high intensity involves a lot of central nervous system training, often overlooked until you're doing it.) In the end, I just question these recommendations to "stand vs sit", because neither of these things are going to really challenge your body. My sense is that unless you significantly challenge the combination of strength, flexibility, and aerobic capacity with some regularity, what you do in low-intensity situations will only change you in a minor way. Subsequently, my guess is that if you actually measured athletic performance (standing vertical jump, V02 max, etc) of someone who sat all day at work vs stood up all day at work, there probably wouldn't be much of a change. And as a corollary, I'd expect if you found a way for people to actually improve their athletic performance significantly, that would likely have a significant effect on their quality of life as they age. Unfortunately, most athletic studies are performed at colleges on a fixed demo, e.g., college athletes. I'm just not aware of anyone looking at long term effects of athletic performance for the average joe in the workforce. It would be an expensive proposition, too, so I'm not sure it'll be forthcoming.