Circadian Rhythms and the Scale
Wellness Jan 13, 2016
Circadian Rhythms and the Scale

While it may seem unlikely that changes in exposure to light and darkness can have an impact on health, the study of Chronobiology suggests otherwise by examining how we are affected by light directed circadian rhythms. Light engages our circadian molecular clocks, which are thought to control up to 30 percent of our genes and affect things such as hormones connected to appetite. Consider your own schedule to determine if inadequate or irregular daylight exposure could be affecting your weight.


Light is the primary influencer of genes that control internal clocks. The hours you are exposed to light affect different bodily functions, such as immunity, metabolism, cardiovascular system, digestion, and hormonal balance. A key player in weight management is the appetite suppressing hormone leptin, levels of which are decreased by shift work, whether it’s sleeping during daylight and working at night, or changing your sleep wake schedule often.

A Boston study involving participants who had their daylight exposure disrupted by switching to a 28 hour schedule revealed decreased leptin levels in the test subjects’ blood. Lower leptin levels increases appetite and weight gain.

Chronodisruption, or a disturbance in circadian rhythm, also reduces nocturnal production of melatonin, a hormone that helps regulate sleep. Technological advancements have enabled us to banish darkness around the clock, and as a result have suppressed melatonin from being adequately produced after dark. University of Granada researchers discovered that melatonin can control weight gain, pointing to sleep at night as an important strategy for weight maintenance.


In addition to fighting your natural affinity for being awake during daylight hours, regular schedule changes can also create health risks. Night workers continuously disrupt their circadian rhythms with even small exposures to sunlight on their days off, as they attempt to connect with day-shift friends and family. As a result, their schedules never really settle into a nocturnal existence and they remain at risk for health complications such as obesity.


Jet lag, while seemingly harmless, can also be a risk factor for weight gain. Researchers from Israel’s Weizmann Institute of Science used fecal samples from mice and humans to determine that gut bacteria is subject to changes triggered by alterations in light exposure, resulting in weight gain and metabolic complications in the subject mice.

Our biological clocks, which drive circadian rhythms, are dependent on consistent patterns of light and darkness in order to function optimally. While it may now be possible to work and enjoy recreational activities around the clock, there are potential weight-control challenges associated with schedule disruption that shouldn’t be ignored.