Is Light Pollution Making You Fat?

Artificial light—everything from electronics to city streets—is now suspected as a contributing factor in soaring obesity rates. To stay thin, go dark!

Smartphones have gotten us through many sleepless nights:

or so we might think. Though many of us now instinctively reach for the devices during moments of wakefulness, assuming a leisurely scan of Twitter or Facebook might help lull us back to sleep, doing so not only doesn’t work—using electronic devices in the middle of the night makes it harder to go back to sleep—but it may actually be causing long-term damage, including seriously compromising our waistlines.

A comprehensive review published this week by the Endocrine Society suggests that increased exposure to artificial lights at night—something that’s already been identified as a contributor to cancer risk—disrupts our circadian rhythms and very likely contributes to soaring obesity rates worldwide. It’s not just tablets and phones doing the damage, either: light leaking in through windows, hallway light sneaking under the door, or even green or orange glows emanating from clocks at our bedside can all contribute to our lack of quality slumber, which ultimately is the heart of the problem.

The mechanism at play here is a disruption in our metabolism—the genes involved in nutrient metabolism behave in rhythmic patterns, and metabolically related hormones such as glucagon, insulin, ghrelin, melatonin, and leptin, are released in sync with circadian cycles, according to the report. Because circadian rhythms are synced most directly to the external environment by light information, exposure to light at night—and the impact that causes to our sleep quality—can compromise your system’s effectiveness. “This complex biological clock system—one clock in brain and multiple clocks in the body—can be put out of alignment,” says Endocrine Society spokeswoman Eve Van Cauter, Ph.D. “That in and of itself has adverse metabolic affect.”

In effect, the more artificial light intrudes upon your bedroom, the lower your sleep quality becomes, and the more your body’s ability to process nutrients becomes compromised. As a result, your weight creeps up over time. In fact, the review, conducted by researchers at Ohio State University, found that geographic obesity rates in the United States increased in tandem with growth in light pollution over the last 20 years.

Since black is slimming, after all, your play might seem obvious—turn out all the lights! But it’s more than that: Avoid bright screens before turning in (or at least dim the device as much as possible) and definitely shun them during your wakeful periods—the blue light from smartphones and tablets is the most disruptive, Van Cauter says. Also, do everything you can to mute any external light encroaching on your bedroom, whether it’s by purchasing thicker curtains, covering your clocks, or installing light-blocking door sweeps. “I live in downtown Chicago, where there’s no such thing as total darkness,” says Van Cauter. “I sleep with a mask on every night.”


Is Light Pollution Making You Fat?