This could be because they make the effort to find privacy to talk away from their desk, the researchers said.
The US study used chest sensors to track movement and heart rate in hundreds of people in different buildings over three days.
The potential health benefits should not be ignored, they said.
But they said the study was observational only and factors like location of stairs and lifts could be at play too.
The University of Arizona study, published in Occupational & Environmental Medicine, claims to be the first to measure activity and stress in office workers, rather than asking them in a survey.
It said office workers tended to be a sedentary group compared to other workers, making them more likely to have health issues, including heart problems, tiredness and low mood.
Being less active during working hours has also been linked to greater feelings of stress.
- Office cake is ‘danger to health’
- Could offices change from sitting to standing?
- Office workers ‘too sedentary’
In the study of 231 office workers in government buildings in the US, those in open-plan offices – with no partitions between desks – clocked up 32% more physical activity than workers in private offices and 20% more than those in cubicles.
And those who were more active had 14% lower levels of stress outside the office compared to those who were less active.
Participants in the study also answered questions about their current mood every hour on their smartphones during work time.
Older office workers were more likely to have higher stress levels. The most stressed people at work were also those who were highly stressed at home too.
On the whole, men were more active than women.
Esther Sternberg, study author and professor at University of Arizona College of Medicine, said: “We all know we should be increasing our activity but no matter how we try to encourage people to engage in healthy behaviour, it doesn’t work for long.
“So changing office design to encourage healthy behaviour is a passive way of getting people to be more active.”
Although people tend to like individual offices or cubicles more because they are more private, the researchers found open plan offices could have other benefits, such as better communication, more impromptu conversations and increased awareness of colleagues.
The researchers said other design features could also affect activity levels – such as how people circulate in their offices, where meeting spaces are located and how accessible stairs and lifts are.