Sitting is correlated with fat metabolism issues, but standing for periods of just 10-15 minutes is correlated with vascular disease; standing was shown in studies to correlate with increased stress hormones and increased blood density.
[Citation needed]
This isn't meant as a threat, either: I'd be quite interested in a comprehensive literature review of this stuff.
It reminds me a bit of the brouhaha around barefoot running: some decent evidence suggests barefoot is "better," while some suggests that forefoot striking is really the key. Expert opinion is split.