Last updated on April 6th, 2018

Many people recognize that factors like too little exercise or too many calories can lead to obesity.  A lesser-known risk factor for obesity is lack of sleep, which is suspected to cause hormonal changes affecting a person’s appetite. This is why a group of scientists at the Institute of Cancer Research in London decided to investigate what initially sounds like an unlikely pairing: how too much light in the bedroom correlates with obesity.

The research team, led by Dr. Emily McFadden of the University of Oxford, worked together with Breakthrough Generations, a UK study of the causes of breast cancer.  Breakthrough Generations is following 113,000 female study participants for 40 years to identify the root causes of breast cancer, such as obesity.

Obesity and breast cancer risk

Obesity is known to be a major risk factor for breast cancer.  In post-menopausal women, studies have found that obese women who were not taking hormone replacement therapy had 2.5 times greater risk of developing breast cancer.

Findings from longer term cancer research have found that postmenopausal women who are overweight or obese have a higher chance of getting breast cancer. This elevated risk is believed to be caused by the production of higher levels of estrogen from excess fat tissue.  The estrogen in turn can fuel the growth of breast tumors.

Additionally, according to Professor Anthony Swerdlow,

 ‘Metabolism is affected by cyclical rhythms within the body that relate to sleeping, waking and light exposure.’ Source

What’s ‘light’ got to do with it?

As part of the study, women were asked to rate the amount of light in their bedrooms at night, ranging from “Light enough to read” to “too dark to see your hand, or you wear a mask.”
Analyses found that the lighter a bedroom was, the more likely that bedroom was associated with an obese individual.

Dr. Swerdlow’s team isn’t quite sure of the sequence of events.  Which came first, sleeping with light bedrooms, or the obesity? Did one cause the other? However, Dr. Swerdlow’s findings were consistent with previous research by Ohio State University and the American Medical Association.  This study doesn’t give enough evidence that making bedrooms darker would affect your weight, but it has led scientists to come up with some hypotheses for the association.

How light affects sleep and your waistline

We all follow a set of biological rhythms, synchronised with the 24 hour cycle of day and night. This ‘body clock’ regulates not only sleep patterns, but many other processes including body temperature and hormone production. One of the major influences on these circadian rhythms is exposure to light.

Research indicates that disruption to normal light exposure may affect carbohydrate metabolism. Previous studies suggest that the blue light from iPad screens and other gadgets reduce the amount of the sleep hormone melatonin we produce at night.

Another theory is that women sleeping in light rooms sleep less in general.  There’s also good reasons to believe that sleep loss may be linked with weight gain and obesity.

To make things worse, those people sleeping with extra light in their bedrooms are generally unaware of the light. Sleep scientist, Derk-Jan Dijk believes there is no harm in trying to make bedrooms darker and that blocking out light pollution from streetlights, digital clocks and other electronic devices may be a healthy preventative strategy.

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Disclaimer: The views presented in my writings are my own and mine alone. They do not reflect any of my past or future employers, or past or future universities I am affiliated with. The information contained in my articles is for general information purposes only. My articles do not represent professional medical care, advice, or endorsement of any product or service, and should not be treated as such. You must not rely on the information in these article as an alternative to medical advice from your doctor or other professional healthcare provider. If you think you may be suffering from any medical condition you should seek immediate medical attention. You should never delay seeking medical advice, disregard medical advice, or discontinue medical treatment because of information on this website. Read SleepJunkies.com‘s full disclaimer: https://sleepjunkies.com/medical-disclaimer/. Disclosure: Ms. Uno has no relevant financial or nonfinancial relationships to disclose.

Photo by Flameeyes

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