Physiotherapists warned that firms were risking the health of their business if they did not encourage better working habits.
One in five people surveyed for the Chartered Society of Physiotherapy (CSP) and health insurer Aviva revealed that they worked through their lunch every day.
Of those who do manage to take a break, half said they ate at their desk. Only one in five left their workplace to go outside for a break, and only three per cent went to the gym.
Karen Middleton, chief executive of the CSP, said: "Full-time workers spend a significant bulk of their week at work, or travelling to and from it. Finding ways to build in time to do at least 30 minutes of moderate intensity physical activity, five times a week, can be a challenge. The consequences of not doing so can be devastating, with many people suffering ill-health and prolonged spells off work.
"The price of inactivity for employers can be vast, with higher sickness absence costs and lower productivity."
About 2000 adults were surveyed for the study.