I bought a standing desk (just an adjustable drafting table) for my office and got a drafting chair as well after hearing this story months ago. The drafting chair isn't so comfortable, and I sometimes get knee pain if I lock my knees for a long time, but overall it's been MUCH better than sitting all day. I feel more energetic, I don't get groggy and sleepy AT ALL, even after a heavy lunch at my favorite Chinese restaurant.

Haven't seen any noticeable weight loss. Also, not having an arm rest all day has led to some minor shoulder pain, but it was easily alleviated by minor massage therapy for a few days and by being more aware of whether I'm "holding up" my arm or resting it on the desktop.

I bought a mechanized sit-stand desk 10 years ago, and cannot imagine living without it. Depending on the task at hand, I switch between standing and sitting on an inflatable exercise ball probably 8 or 10 times a day.

There's a DIY version available online:
http://www.geekdesk.com/default.asp?contentID=605
(FWIW, I have no vested interest in the product, except hope that it might help others.)

I'm emailing this while standing -- thanks to your guest, Arianne Cohen. After hearing her the first time, I went wireless and now stand at least half my computer time. Today, I'm getting the idea of standing when on the phone. Great segment, great insight. Thanks.

What about sitting on a stability (yoga) ball? Core strength?

I used to work at Nickelodeon Studios in NYC with a standing desk that allowed me to work half of the day standing (and dancing to my music). My mind, body, and creativity miss it and now I feel crunched and hunched from my desk chair.

I removed the back off my desk chair to force myself to sit tall and engage my core more. A day of or two later I find it much more comfortable.

What about sitting on a Pilates Ball instead of a chair?

I lay back on my chair as if im laying down.