Employers have been urged to encourage their staff to take decent breaks after a study found that huge numbers are working through their lunch every day.
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 3% went to the gym.
The CSP called on employers to support staff to be more physically active during the working day to reduce their risk of developing musculoskeletal problems like back and neck pain and more serious illnesses such as cancer, heart disease and stroke.
Only a third of workers said their employer provided any kind of exercise opportunities, such as a subsidised gym membership, a lunchtime running club, or an after-work fitness class.
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.
"Free facilities like outdoor gyms, or simply going for a brisk walk at lunchtime, can help people to be more active during the day.
"The consequences of not doing so can be devastating, with many people suffering ill-health and prolonged spells off work.
"Aside from the human cost, the price of inactivity for employers can be vast, with higher sickness absence costs and lower productivity.
"It is in everybody's interests to find ways to tackle the enormous problem of inactivity in the UK and we would encourage people to take responsibility for their own health."
:: Around 2,000 adults were surveyed for the study, which was carried out to mark the CSP's annual Workout at Work day.