Setting an alarm clock before you go to bed could be hazardous to your health, according to research that looks at the body’s internal clock. The study, published in May, shows there’s about a one-hour disparity between how much sleep adults get during the week versus the weekend. It also revealed that over the past decades, people have been going to bed later and getting up earlier, resulting in an average of 40 minutes less sleep per night.
Why does any of this matter? Because, according to the researchers’ conclusion, messing with your body’s biological clock can increase your risk for obesity.
Previous studies have linked sleep deprivation with excessive weight, but Roenneberg’s team concludes that it isn’t just how much sleep people get that matters—it’s how much they mess with their internal clocks. For every hour of social jet lag accrued, the risk of being overweight or obese rises by about 33 percent. Obesity results from a host of influences, but Roenneberg says “one contributing factor is not living according to your biological temporal needs.” No one knows the precise mechanism, but other studies suggest that lack of sleep causes higher secretions of ghrelin, the appetite hormone, and a reduction of leptin, the satiety hormone.
Our daily lives are controlled by two naturally occurring phenomena: our internal circadian clock and the rotation of the earth. The hub of the body clock resides in a bundle of nerves called the suprachiasmatic nucleus, in the brain’s hypothalamus. This central clock acts as a pacemaker, synchronizing other cellular clocks that scientists believe exist throughout the body. This circadian clock system controls a variety of functions, including body temperature, hormone secretion and blood pressure. It also regulates the daily activities of organs.