Many of us lead a double life. We stay up late, hanging out with friends or watching television. The next morning, we wake to the blaring of the alarm clock, even though our body cries out for more sleep.
The timing of our social and work commitments is increasingly at odds with our internal clock, leading to “social jet lag.” In order to make up for lack of sleep on workdays, we spend more time in bed on weekends.
This type of chronic sleep deprivation has severe implications for our health. People suffering from social jet lag are more likely to smoke, as well as drink caffeine and alcohol. Now it appears that social jet lag may also contribute to obesity.
Using an online survey, researchers collected information from 65,000 people about their height, weight, and sleep patterns.
The results, published in Current Biology, show that living “against the clock” is linked to an increased body mass index—a combination of height and weight that is used to estimate body fat. This was true only for people who were already overweight, not for those with normal weight.
Our bodies run on an internal physiological clock that is set by the pattern of daylight and night-darkness. This clock provides the optimal window for sleeping and waking. It varies among people, and is influenced by genetics, age, sex, and environment.
Social jet lag isn’t just about being tired or overweight. A range of conditions is related to obesity, including type 2 diabetes, cancer, and heart disease.
Relief from the chronic sleep deprivation of our modern lives may require more than going to bed at a decent hour. Lack of time spent in bright sunlight, as well as Daylight Savings Time, can also throw off our internal clock.