Researchers found that the rhythms in metabolism in night workers were flipped completely, such that these rhythms in these metabolites had adapted to the night work schedules almost completely, reports Spokane Public Radio.

“Ah ha” moments don’t happen very often for scientists, but world-renowned sleep researcher Hans Van Dongen at WSU Spokane experienced one recently.

One of Van Dongen’s emphases is looking at the physiological effects of working swing and graveyard shifts.

People were meant to be active during the day and to sleep at night. And when that order is reversed or somehow altered, it throws off a person’s internal clock. That can lead to big problems, for example, if a tired person with some important responsibility makes a mistake on the job. He and others also say people who work odd shifts also face a greater chance of contracting diabetes and becoming obese.