Hold the Phone: Light exposure at night may affect weight gain

Those late night games of Candy Crush Saga in bed may be taking a toll on more than just your nightly sleep schedule.  A recent medical review suggests that all of those nighttime texts and tweets could have an effect on our waistlines (and not in a good way)[1].

Researchers suggest exposure to light at night, even electric light like the kind that pops off the screens of our iPhones, tablets and other devices, may disrupt our circadian system [1]. This system helps guide our normal sleep and wake schedules by regulating rhythm within the human body and can alter functions in our metabolism that are related to nutrition [1] [2].

A recently published study on mice found that even mild changes in light exposure altered circadian and metabolic functions, and could help researcher better understand its connection to obesity and disorders related to sleep and the circadian rhythm. [3].

New research suggests exposure to light during the night may have an impact on weight gain. Source: Katie Golde

New research suggests exposure to light during the night may have an impact on weight gain. Source: Katie Golde

An additional study published in 2010 found that exposing mice to light at night disrupted their food intake and other metabolic signals, resulting in weight gain. Mice that were exposed to either dim or bright light saw an increase in body mass compared to mice who were exposed to a regular light/dark cycle, despite being fed the same caloric intake and activity levels [4].

Study authors say the data is relevant to the increase in human obesity due to the use of light usage at night and shift work (or maybe pulling all-nighters the week before finals) [4].

While the data may be relevant, medical experts warn that we don’t have all of the information yet.

“It’s an intriguing observation and raises a lot of questions about how we might come to understand weight regulation,” says Dr. Joseph T. Bass, Professor of Medicine in the Department of Medicine of Feinberg School of Medicine and the Chief of the Division of Endocrinology, Metabolism and Molecular Medicine at Northwestern University.

Bass says that light exposure at night can affect the circadian clock, but the mechanism behind the relationship between light cycles, food intake and our endocrine system remains unclear.

“Appetite is regulated very differently at different times of the light/dark daily cycle and exactly how that influences body weight we don’t really understand,” says Bass, who also says the concept that there is some sort of relationship has been well proven.

Global health experts have also expressed concern about exposure to artificial light during the night. The 21st International Congress of Zoology met in Haifa, Israel in 2012 to discuss the possible ramifications of increased usage of artificial light and its affect on the circadian system.

The University of Haifa, where the conference was held, reported that an international panel discussed the extent and harm of artificial light usage after dark. A statement from the university’s media relations noted that conference participates, “were in full agreement that exposure to light at night affects circadian rhythms in nature – humans, animals and plants – which when thrown off can result in various illnesses and adverse symptoms.”

A growing collection of research highlights the health affects of light exposure at night. While more needs to be done to test its relation to weight gain, it might be worth turning off the iPad in favor of an extra hour of sleep (at least tonight).

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