Social jetlag - a syndrome related to the
mismatch between the body's internal clock and the realities of our daily
schedules -- does more than make us sleepy. It is also contributing to the
growing tide of obesity, according to a large-scale epidemiological study
reported online on May 10 in Current Biology, a Cell Press publication.
"We
have identified a syndrome in modern society that has not been recognized until
recently," said Till Roenneberg of the University of Munich. "It
concerns an increasing discrepancy between the daily timing of the
physiological clock and the social clock. As a result of this social jetlag,
people are chronically sleep-deprived. They are also more likely to smoke and
drink more alcohol and caffeine. Now, we show that social jetlag also
contributes to obesity; the plot that social jetlag is really bad for our
health is thickening."
Each of
us has a biological clock, he explained. We
can't set those clocks according to our whims like watches. They are rather
entrained by daylight and night-darkness to provide the optimal window for
sleep and waking. In modern society, we listen to those clocks "less and
less due to the increasing discrepancy between what the body clock tells us and what the boss tells
us."
To find
out how big this problem really is, Roenneberg's team is compiling a vast
database on human sleeping and waking behavior, which they'll eventually use to
produce a world sleep map. Now 10 years into the effort, they already have lots
of information, including participants' height, weight, and sleep patterns.
Their
analysis shows that people with more severe social jetlag are also more likely
to be overweight. In other words, it appears that living "against the
clock" may be a factor contributing to the epidemic of obesity, the
researchers say.
The
findings should weigh in on decisions about Daylight Saving Time, not to mention work
and school times, they add. It would also help if people began spending more
time outdoors in open daylight or at least sitting by a window. As people fail
to do this for one reason or another, their body clocks get set later and
later, leaving them awake into the night and tired by day.
"Waking
up with an alarm clock is a relatively new facet of our lives," Roenneberg
says. "It simply means that we haven't slept enough and this is the reason
why we are chronically tired. Good sleep and enough sleep is not a waste of
time but a guarantee for better work performance and more fun with friends and
family during off-work times." And slimmer waistlines, too.
More
information: "Social
jetlag and obesity" Till Roenneberg, Karla V. Allebrandt, Martha Merrow,
and Céline Vetter, Current Biology online, 5/10/2012. DOI: 10.1016/j.cub.2012.03.038
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