Between this sitting-is-death and the sugar-is-death, there should be tens of millions of dead office workers who died before 60 in the past few decades.
http://www.ssa.gov/oact/STATS/table4c6.html says 12% of all people in the US would die before the age of 60 at current age-group death rates. Currently about 2.4 million people die in the US per year http://www.cdc.gov/nchs/deaths.htm, so probably about 50 million have died over the last three decades. All developed countries together are about triple the population of the US, so 150 million total deaths. Let's say half of these were white-collar workers, or 75 million.
If early death is independent of white-collar status, then you'd expect about 10 million dead office workers who died before 60 in the past few decades, even if sitting and sugar have no effects on death risk.
http://en.wikipedia.org/wiki/List_of_causes_of_death_by_rate