"We didn't find socializing to be the best thing to do during your break unless people were wanting to do that," Trougakos said. "It wasn't bad to be able to work if that's what they really wanted to do," he added.
He and his colleagues collected more than 800 surveys over two weeks that tracked the lunch-time activities of administrative employees at a university. They then asked co-workers' to rate how fatigued those employees were at the end of the day.
The researchers found that workers were least fatigued at the end of the day if they got to relax during lunch. If they worked or socialized, though, the stress was mitigated if they felt it was their choice.
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In other words, some people may prefer a lunch date with their desktop computer to one with their colleagues—and be better off for it.
That doesn't mean it's wise to stay chained to your desk all day. Even if you love your job so much you can barely tear yourself away, Trougakos said you are still likely to be more productive if you can spend at least a bit of the traditional lunch hour thinking about something other than work.
"We have the misconception that when people take a break they are slacking," Trougakos said, when in fact breaks can make workers healthier and more productive.
Workers today probably don't feel as if they have much control over what they can do at lunch. Because of the weak economy, many sense they don't have time for a lunch period, while others may fear that if they take a break they won't be perceived as hard workers.
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Others may be in an office where managers think they are being constructive by pushing colleagues to bond through team lunches, but that well-intentioned effort can backfire.
Federal laws do not require employers to offer lunch breaks, although some states have regulations requiring meal breaks after a certain number of hours.
Trougakos said lunch breaks seemed to be more formalized in the days when more jobs involved physical or manufacturing work. Most people's work now is primarily mental, and people may not realize they need a break, he said.
"Psychologically, it's a different process," he said. "It's harder to tell when we're becoming worn out by our job. We don't really pay as much attention."
—By CNBC's Allison Linn. Follow her on Twitter @allisondlinn and Google, or send her an email.