Light at night increases obesity risk

Posted on Sat, 20 Sep 14

Diet and exercise alone do not explain the obesity epidemic, and one of the strongest emerging risk factors for weight gain is disruption of our natural circadian rhythm from artificial nighttime light exposure.

In many modern industrialized environments the natural darkness of night has been replaced by artificial lights, whether its is the ambient dull light of city streets, the lights that illuminate your house, or the screens you are staring at.

The human body has evolved, however, to synchronize with natural light and dark cycles and disrupting this natural rhythm can have untoward consequences including metabolic disturbances that result in weight gain.

In support of this idea a recent study of 100,000 women aged 16 years or older living in the United Kingdom found that exposure to light at night significantly increased the risk of obesity, even when controlling for potential confounders such as sleep duration, alcohol intake, and physical activity.

“The results from this study suggest that light exposure at night could play a role in the etiology of obesity in some individuals” says Dr. James Gangwisch from Columbia University who has been studying the effects of sleep disruption on metabolic health. “If metabolic changes resulting from nighttime light exposure are contributing to the obesity epidemic, it may be beneficial to take measures to limit this exposure."

“At an individual level, we can take measures to ensure that our bedrooms are dark at night by hanging blackout curtains and hiding or covering up light-emitting diodes and luminous clocks” says Dr Gangwisch.

References:

1. McFadden E, Jones ME, Schoemaker MJ, Ashworth A, Swerdlow AJ. The relationship between obesity and exposure to light at night: cross-sectional analyses of over  100,000 women in the breakthrough generations study. Am J Epidemiol. 2014 Aug 1;180(3):245-50.
2. Gangwisch JE. Invited commentary: nighttime light exposure as a risk factor for obesity through disruption of circadian and circannual rhythms. Am J Epidemiol. 2014 Aug 1;180(3):251-3.