Working the night shift burns less energy and increases risk of weight gain

http://www.eurekalert.org/pub_releases/2014-11/uoca-wtn111314.php

PUBLIC RELEASE DATE: 17-Nov-2014

Contact: Kenneth Wright
University of Colorado at Boulder
Working the night shift burns less energy and increases risk of weight gain

People who work the night shift are likely burning less energy during a 24-hour period than those on a normal schedule, increasing their risk for weight gain and obesity, according to a new study led by the University of Colorado Boulder.

Researchers have known that people who work, and therefore eat, at night when their bodies are biologically prepared to sleep are prone to put on pounds. But the reasons have not been clear.

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The researchers found that total daily energy used by participants decreased when they were put on a shift work schedule. The reduction is probably linked to the mismatch between the person's activities and their circadian clocks, Wright said. Humans have evolved to be awake--and eat--when it's light outside and sleep when it's dark. In large part, the human circadian clock is set by exposure to sunlight.

People's circadian clocks can shift over time--even radically--with the use of artificial lights if they aren't exposed to the sun. But because shift workers typically switch back to a daytime schedule on their days off, their biological clocks don't flip to fit their night shift schedules.

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