Is Artificial Light a Cause of Obesity?

Small boy looking at tablet
Thanasis Zovoilis/Getty Images

Poor dietary habits and a largely sedentary lifestyle have been the combination that has played perhaps the most significant role in the obesity epidemic. A number of other causes, including some that are related to this combination, have been identified as contributing factors in the obesity epidemic. Artificial light at night appears to be one of those.

Bright Light at Night

Artificially increasing the length of daytime by using indoor lights has been linked to a number of diseases, from breast cancer to obesity.

Artificial light affects our circadian rhythms and can throw off normal metabolism. Scientists have found that this occurs at the most basic molecular level. These changes, in turn, can lead to weight gain and obesity.

The Dangers of Screen Time

“Screen time” refers to all the time we are increasingly spending looking at screens of all types—including computer and tablet screens, phone screens, television screens, gaming screens, and the like. By all accounts, the amount of time spent by both children and adults in front of various screens has increased exponentially in the past few decades.

All this extra screen time has been shown to have poor effects on our health, too. In one study of over 13,000 Spanish university graduates, television viewing was found to be directly associated with premature death from any cause.

In addition, multiple studies have found that a sedentary lifestyle is associated with obesity.

One such study found that more sitting at baseline was associated with increases in body mass index (BMI) over time. This holds true for children and adolescents as well. Another study of adolescents who were followed every 6 months from age 14 to age 18 found that greater screen time was associated with adolescent obesity.

Other studies have shown that too much time in front of the television promotes unhealthy eating habits.

Screen Time and Lost Sleep

Several studies have now established that the blue light emitted by LED screens suppresses melatonin production and thereby interferes with the ability to fall asleep. In turn, chronic sleep deprivation is associated with weight gain and overeating.

To optimize your chances of falling asleep and staying asleep, make it a habit to turn off all screens at least an hour before going to bed. Since the light emitted from computer, phone, and tablet screens can be particularly harmful when it comes to suppressing melatonin and disrupting circadian rhythms, plan to turn those devices off two or more hours before bedtime.


Wyse CA, Biello SM, Gill JM. The bright-nights and dim-days of the urban photoperiod: implications for circadian rhythmicity, metabolism and obesity. Ann Med 2014;46:253-63.

Kim YJ, Park MS, Lee E, Choi JW. High incidence of breast cancer in light-polluted areas with spatial effects in Korea. Asian Pac J Cancer Prev 2016;17:361-7.

Fonken LK, Aubrecht TG, Melendez-Fernandez OH, et al. Dim light at night disrupts molecular circadian rhythms and increases body weight. J Biol Rhythms 2013;28:262-71.

Borodulin K, Karki A, Laatikainen T, et al. Daily sedentary time and risk of cardiovascular disease: the National FINRISK 2002 Study. J Phys Act Health 2014 Aug 22 [Epub ahead of print].

Mitchell JA, Rodriguez D, Schmitz KH, et al. Greater screen time is associated with adolescent obesity: a longitudinal study of the BMI distribution from ages 14 to 18. Obesity (Silver Spring) 2013;3:572-575.

Figueiro MG, Bierman A, Rea MS. A train of blue light pulses delivered through closed eyelids suppresses melatonin and phase shifts the human circadian system. Nat Sci Sleep 2013;5:133-141.

Continue Reading