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Managing Your Weight in The Dark

Readers will recall a post earlier this week on the importance of sleep for weight management.

Researchers and clinicians, wanting to know more about the underlying biology and mechanisms on how lack of sleep, disruption of circadian rhythm (e.g. through shift work, jet lag, or having a baby), and alterations in light/dark cycles can impact ingestive behaviour and energy metabolism may wish to read a comprehensive review just published in the Annals of Medicine.

In this paper, Russel Reiter and colleagues from the University of Texas, San Antonio, summarize the potential contributions of three processes that may be contributing to humans becoming progressively more overweight: circadian or chronodisruption, sleep deficiency, and melatonin suppression.

As the authors point out:

Circadian disruption, sleep deficiency, and melatonin suppression have at least one common causative feature, i.e. excessive light exposure including even brief periods of light at night. Indeed, interrupting the normal dark period with a short interval of bright light may be the most disruptive. Certainly, light pollution throughout the world, and especially in the economically well developed and developing nations, where obesity is also the most common, has become a major problem and is a serious concern. The use of artificial light after darkness onset in the evening and in the morning before sunrise is commonplace and impacts the physiology of the circadian system which influences both nocturnal melatonin synthesis and sleep. Moreover, being exposed to light after darkness onset due to what is referred to as trespass light or intentionally turning on a lamp is disruptive to the circadian system, which reduces melatonin levels and disturbs sleep.

Obviously, looking at bright light sources such as a TV, a computer screen or a backlit e-Book can be even more disruptive.

Perhaps we should now all plan for candle-light dinners and then call it an early night?

Leipzig, Germany

Reiter RJ, Tan DX, Korkmaz A, & Ma S (2011). Obesity and metabolic syndrome: Association with chronodisruption, sleep deprivation, and melatonin suppression. Annals of medicine PMID: 21668294


  1. “Perhaps we should now all plan for candle-light dinners and then call it an early night?”

    You’re too funny, Dr. Sharma!!

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  2. So I suppose that opening the fridge in the dark is pretty disruptive too, no?

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  3. Hi, Dr. Sharma.

    This is a massive problem. And that is an understatement. Canada and the United States need to pass light pollution/light trespass laws EVERYWHERE. Some states have them.

    I have been saying all along that light pollution is a HUGE contributor to obesity , not to mention that lack of sleep destroys a person’s health and puts them at risk for all sorts of diseases.

    I am putting a link to you at my blog. I hope EVERYONE pushes for very strict light pollution laws after reading your article. ( The only exceptions being airports for obvious reasons)

    Take care,


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  4. A agree with Razwell’s comments. There have also been studies showing increases in crime in well lighted neighborhoods. Huh? Yep, apparently criminals don’t like being forced to use flashlights during night time robberies and break-ins–too obvious and increases their liklihood of been noticed compared to robbing places that have lots of night time lighting for “crime prevention” purposes. I can’t convince my neighbors of this, however, whose front porch light is like a spot light in my bedroom windows. I hate having to close up the house at night because, well, I like fresh air and sleep much better when I know I can be alerted if there is anyone outside on my property (my old dog doesn’t hear as well through closed windows.) Anyway, I have made home made felt over cardboard to block light, and am forced to use air conditioning in summer. It’s a crappy set of options. I need my sleep.

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  5. People need good sleeping conditions to be healthy. When my husband is restless, he moves to the living room to sleep. We have no hallway light on at night because it glares into my bedroom like sunshine. I have a wave machine to block the sounds of the night.

    When I sleep well, I have much less cravings during the day. Lack of enough quality sleep and cravings are definitely connected. Some of your recent posts explain the medical/scientific reasons why. I know it from experience.

    🙂 Marion

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