One in four people in the UK often works all day without taking a break, a survey suggests.
More than half of the 3,000 people polled by the Chartered Society of Physiotherapists said they went to work when feeling unwell or stressed.
Staff shortages were cited as a cause of stress and why breaks were skipped.
While work can contribute to people's mental and physical well-being, overworking can lead to health problems, the CSP warned.
While a quarter of those polled took no lunch break at all, a third worked through most of theirs. Half of those who did so said it was because they had too much work to do, and a third because there were not enough staff to do the work required.
Working in the same position for long periods at a time meant many complained of physical pain.
The CSP warned that poor working practices increased the risk of chronic musculoskeletal disorders, like back pain - one of the most common reasons for long-term sickness leave in the UK.
Stress was also an issue, with more than 40% feeling stressed at least once a week. For many of these people, staff shortages and a heavy workload were at the root of their anxiety.
Last year, the health watchdog NICE urged employers to do more to tackle stress and anxiety in the workplace.
Sickness absence and "sickness presence", when staff come to work feeling unwell, is estimated to cost employers and society about £35bn each year in reduced productivity, sick pay and benefits.
At least some of this could be recouped through healthier working practices and helping employees access treatment for musculoskeletal disorders, the CSP said.
"Work is good for us and can contribute to our physical and mental well-being - but not when overworking means people don't have the time or energy to look after their own health or when staff are at work but not fit for work," said Ann Green, chairman of the CSP.
Ben Willmott, of the Chartered Institute of Personnel and Development, said: "These findings should ring alarm bells for employers.
"A certain level of pressure at work is of course desirable. However when the pressure people face exceeds their ability to cope - in other words stress - it is likely to lead to time off work and is linked to conditions such as depression, anxiety and heart disease."