Is sitting at your desk all day unhealthy?

I remember reading “The Westing Game” by Ellen Raskin as a kid, and one of the characters is described as “wide-hipped” from 30 or 40 years of “secretarial sitting.” Is this a legitimate effect of desk-sitting, or does it fall into the category of creative liberty?

Essentially, if you sit at a desk for 8 hours a day, 5 days a week, however many years you work at a desk, are you going to see physical effects? Are there ways to counteract such effects?