People who work outside typical working hours, such as working overtime or working on shift, are more likely to develop metabolic diseases such as obesity and diabetes while disturbing biological clock in the digestive system.
A team of researchers led by Professor Debra Skene at the University of Surrey in Britain conducted a study of 14 American men and women and published the results on Proceedings of the National Academy of Sciences of the United States of America (PNAS).
The test subjects were asked to stay at the research lab for a week. Researchers divided the subjects into two groups, one for daytime and the other for nighttime activity. And they kept the brightness and the temperature of the room constant so that the subjects could not tell what time it was and fed the subjects at a scheduled time. After that, researchers analyzed 132 indicators from the blood sample.
As a result, 20 percent of the metabolites regulated metabolism by changing their concentration every 24 hours, which means a biological clock that controls the rhythm of physical activity, was working.
What was noteworthy about the result was that most (89 percent, 24 indicators) of the substances controlling metabolism were produced up to 12 hours late for those who were active at night. Metabolites produced during digestion were particularly disturbed. For example, the blood sugar level, which normally increases before and after a meal, increased later. In contrast, the clock in the central nervous system slowed by two hours at most.
“Working overtime for three days is enough to destroy metabolism if the biological clock in the brain and digestive system is out of sync,” said Skene. “Further studies on cell and hormone changes could help treat the symptoms.”