Humans

Weight Gains In Humans Regularly Exposed To Night Light

A popular study in the discourse of the effects of light pollution on humans is the association between light and obesity. The National Institute of Environmental Health Science (NIEHS) conducted a particularly large-scaled study, using data from over 43,000 women in America (NIEHS, 2019). Before the study commenced, they noted that women who slept with the light or television on were more likely to be obese at the start of the study. In the follow-up period of 5.7 years (on average), these women were also 17% more likely to have gained approximately 11 pounds (NIEHS, 2019). 

Interestingly, another study conducted on nurses and midwives found that a switch to working night-shift resulted in an increase in their BMI over the course of 2 years; and accordingly, nurses or midwives that switched from nighttime to daytime-shifts recorded decreases in their BMIs (Live Science, 2013). 

Such studies suggest that light exposure does adversely affect our weights. But how does the intangible light exposure influence such tangible effects of fat deposition?

 

Light to Fats

While the correlation between light and obesity has yet to be established, several studies have proposed possible explanations behind this association. 

First, light can affect our metabolism. Long exposure to light is speculated to result in weight gain through a specific fat type called the brown adipose tissue (BAT). This tissue is highly influential in determining energy expenditure (i.e. it helps us to burn calories) (Makris, 2019). Some researchers believe that exposure to artificial light at night tricks an evolutionary adaptation that was developed earlier by our ancestors which involves the storing of fat in summer months to prepare for colder and darker winter (Makris, 2019). While BAT activation increases in the winter to produce heat for warmth, conversely, when our bodies believe it to be summer (determined by longer day-length), it stores excess fat for the future (Makris, 2019). Since our body responds to the ‘day-length’, and ‘day-length’ is determined by light, exposure frequency and duration to artificial light at night has the potential to fat deposition. 

Another common explanation provided is the indirect effect of light-induced sleep reduction which may reduce physical activity and/or disrupt stress and appetite hormones, leading to a possible increase in food consumption (Rettner, 2019). 

While the correlation between light exposure and obesity, like many of the other light impacts on human health, remain relatively undetermined, they all point to a common trend that reducing artificial light at night is generally beneficial to us. While it might be easier to wait for scientifically established data to tell us that light is bad for us, let’s take a step of precaution before its too late!

Till next time!

Trudie

 

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