A new study has found that people with unhealthy habits - such as smoking, eating badly and not exercising - are less productive at work.

The study - carried out by the Erasmus Medical Centre in Rotterdam and published in the Occupational & Environmental Medicine journal - found that in addition to being unproductive, employees with unhealthy lifestyles are more likely to take sick leave and will take longer to get back to work when they do take time off.

Between 2005 and 2009, Alex Burdorf and his associates surveyed more than 10,600 people who worked for 49 different companies in the Netherlands.

Participants were asked to discuss both lifestyle and work habits, rating their work productivity on a scale of 0 to 10, while offering information about their weight, height, health history and the number of days they had to call in sick during the prior year.

Researchers found that 56 per cent of those polled had taken off at least one day in the preceding year because of poor health. Being obese, smoking, and having poor diet and exercise habits were contributing factors in just over 10 per cent of sick leave occurrences.

In particular, obese workers were 66 per cent more likely to call in sick for 10 to 24 days than normal weight employees, and 55 per cent more likely to take time off for 25 days or more.

Smokers also took more sick leave, translating into a 30 per cent greater likelihood that a worker would take off 10 to 24 days because of poor health. By contrast, those who drank 10 or more glasses of alcohol each week were actually less likely to take time off for poor health.

Overall, the team found that weight appeared to be a key factor in whether or not an individual had an underlying health issue that might prompt needing sick leave. Among obese workers, 83 per cent said they had developed at least one disease, compared with 75 per cent of overweight workers and 69 percent of normal weight men and women.