Research: Turn out the lights and lose weight

Research - Boggle LettersResearch - Boggle Letters

Darkness prior and during sleep may reduce weight gain


Light has long been known as the enemy of good sleep.  From the standard night light to the relatively new blue light sources created by our electronic lifestyles, we have been bombarding our eyes with light that inhibits our ability to get a good night’s sleep.  Most of us wish we could get a good night’s sleep with peace like that of a small child or baby.  The light increases cortisol and suppresses melatonin levels.  Melatonin is a natural signal to sleep, and without proper levels, you will not sleep well.  Exposure to light and in particular blue light at night doesn’t just interrupt your chances of a great night’s sleep, but it may also increase your risk of weight gain and inhibit weight loss.  

What is new is that we are beginning to understand the intricate relationship between sleep and obesity.  A study published in the American Journal of Epidemiology in 2014 looked that data for over one hundred thousand women from the Breakthrough Generation Study.  The study was entitled “The Relationship Between Obesity and Exposure to Light at Night: Cross-Sectional Analyses of Over 100,000 Women in the Breakthrough Generations Study”​.  The researchers looked at the data of a questionnaire and adjusted the analysis for age, socioeconomic status, working night shifts, having children under 5, alcohol consumption, sleep duration, and current smoking status.  They did this to adjust for other potential influences on weight. The researchers found that women were less likely to be overweight to obese if they slept in a dark room.  

So what does this mean?  This tie is not a causal relationship, but it probably points to a potential link.  Since it is a cross-sectional study, it only highlights a potential relationship.  The researchers did a good job looking for potential confounding causes, but it is possible that there may be an unknown confounder that mucked up their results.  More research is needed, but the results make sense.  Light hinders melatonin and sleep, and poor sleep has been tied to obesity.  Many will argue that for the average person this study does not provide any convincing evidence that you should darken your room at night, it just makes sense to darken the room and avoid electronics an hour before bedtime.  It will allow you to wind down and sleep better.

Pop Privacy Tent
Pop Privacy TentMay help lock out some light and help sleep.  

The bottom line: I recommend you sleep in a dark room and avoid the use of electronic devices 1 hour before bedtime.  Even though studies are needed to confirm the tie between weight loss/gain and sleep, I will say that it may not help you lose weight, but it will help you sleep better and will make weight loss or maintenance easier.  Try the Pop Privacy Tent on your bed to block out some light.  I have had one for two weeks, and I love it.  It has helped my sleep immensely.  


  1. McFadden, E., M. E. Jones, M. J. Schoemaker, A. Ashworth, and A. J. Swerdlow. “The Relationship Between Obesity and Exposure to Light at Night: Cross-Sectional Analyses of Over 100,000 Women in the Breakthrough Generations Study.” American Journal of Epidemiology 180, no. 3 (May 29, 2014): 245–50.

Recommended sleep aid:

Print Friendly, PDF & Email

About the Author

I am a family physician who has served in the US Army. In 2016, I found myself overweight, out of shape, and unhealthy, so I made a change to improve my health. This blog is the chronology of my path to better health and what I have learned along the way.

Be the first to comment on "Research: Turn out the lights and lose weight"

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.