Are Your Light Bulbs Making You Fat?

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Obesity can result from chronic sleep deprivation and circadian disruption. Exposing the eyes to ordinary light in the hours before bedtime disrupts the circadian rhythm and prevents the flow of melatonin. Special light bulbs that block the blue rays that cause melatonin depletion are available at

There is a global epidemic of obesity with more than a billion people already overweight. It may seem ridiculous, at first, to suggest that ordinary light bulbs are to blame. However, many studies show a strong link between sleep deprivation, disruption of the circadian cycle and an increase in weight, especially in children (1). For example, obesity is much more common among night shift workers (2). But it is not just shift workers that are affected by exposure of the eyes to light at night. In our 24/7 lifestyle, we are all affected.

A very recent study (3) at the University of Surrey in the UK that was funded by Philips (the world’s largest light bulb maker) found ordinary household lighting has a large negative impact on sleep. Studies at Harvard (4) found there is a large decrease in the amount of melatonin produced by exposure of the eyes to ordinary room light during the time the body would normally be producing melatonin. On average, people can produce melatonin for 11.5 hours a night if kept in darkness. Most Americans are in darkness for only 6 or 7 hours a night.

Fortunately, not all colors of light have the same effect on melatonin production. It is primarily the blue rays in ordinary white light that cause the problem. Light bulbs that don’t produce the blue rays were developed by scientists at John Carroll University in 2005. Eyeglasses that block blue rays were also developed and are available at Thousands of people have purchased these products with a guarantee to get their money returned if the glasses do not improve their sleep. More than 90% of customers find the glasses or light bulbs improve their sleep.

Studies with animals have confirmed that exposure to too much light will cause them to get fat (5). The loss of melatonin due to light exposure (that causes the weight gain) can be avoided if melatonin is added to the animal’s diet (6). Exactly how maximizing melatonin prevents obesity is not completely clear. One mechanism (7) involves the production of brown adipose tissue (fat). It can be converted to heat very readily in contrast to white fat. Melatonin stimulates both the production and conversion to heat of brown fat.

Undoubtedly obesity occurs when intake of calories exceeds their outgo. Maximizing melatonin to promote sleep and help convert fat to heat will be helpful. Avoiding blue light with special light bulbs or glasses in the hours before bedtime to maximize melatonin is an easy and inexpensive change in life style.

(1) Int J Obes (Lond). 2012 Jul 24. doi: 10.1038/ijo.2012.119. [Epub ahead of print]
Association between sleep duration and overweight: the importance of parenting.
de Jong E, Stocks T, Visscher TL, Hirasing RA, Seidell JC, Renders CM.

(2) J Occup Environ Med. 2012 Jul;54(7):834-40.
A cross-sectional analysis of the association between night-only or rotating shift work and overweight/obesity among female nurses and midwives.
Zhao I, Bogossian F, Turner C.

(3) J Pineal Res. 2012 Aug;53(1):47-59. doi: 10.1111/j.1600-079X.2011.00970.x. Epub 2011 Oct 24.
The spectral composition of evening light and individual differences in the suppression of melatonin and delay of sleep in humans.
Santhi N, Thorne HC, van der Veen DR, Johnsen S, Mills SL, Hommes V, Schlangen LJ, Archer SN, Dijk DJ.

(4) Clin Endocrinol Metab. 2011 Mar;96(3):E463-72. Epub 2010 Dec 30.
Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans.
Gooley JJ, Chamberlain K, Smith KA, Khalsa SB, Rajaratnam SM, Van Reen E, Zeitzer JM, Czeisler CA, Lockley SW.

(5) Nutr Neurosci. 2009 Oct;12(5):233-40.
Constant light induces alterations in melatonin levels, food intake, feed efficiency, visceral adiposity, and circadian rhythms in rats.
Wideman CH, Murphy HM.

(6) J Exp Pathol. 2007 Feb;88(1):19-29.
Intake of melatonin is associated with amelioration of physiological changes, both metabolic and morphological pathologies associated with obesity: an animal model.
Hussein MR, Ahmed OG, Hassan AF, Ahmed MA.

(7) Bratisl Lek Listy. 2012;113(1):52-6.
Brown fat tissue - a potential target to combat obesity.
Ginter E, Simko V.

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Richard Hansler
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