Monday, October 18, 2010

Sleep and Weight Loss Ties

I've always noticed that my body fat rose and fell as my sleep went from poor to good - IOW, poor sleep, not enough sleep, more fat accumulation.  Only recently have I sorted out how much darkness adds to sleep quality.

"Researchers from Israel and the USA believe they have found evidence that demonstrates a link between obesity and metabolic disorders and exposure to LAN (light at night) in animal studies. In an article published in Proceedings of the National Academy of Sciences they found that mice exposed to dim light during their sleeping hours for a period of eight weeks had a 50% higher weight gain compared to mice that slept in the dark. Even reducing their food intake and making them do more exercise did not bring their weight down to that of the other mice that slept in the dark, unless they made sure the availability of food matched a mouse's natural eating times.

"The 24-hour rhythm that regulates the state of our internal energy levels and metabolism is controlled by an internal biological clock that works in parallel with and responds to light information, the authors wrote. Our internal body clock("circadian clock") prepares us for predictable events, such as the availability of food and sleep. When the function of this clock is disturbed, our bodies experience a disruption in our metabolism and body-rhythms (circadian cycle).

"The investigators assessed the effects of LAN on the BMI (body mass index) of male mice to see whether there might be a casual relationship between exposure to light during the night and obesity."

"They found that mice exposed to light at night had considerably higher BMIs and lower glucose tolerance compared to mice kept in a normal day/night cycle (dark at night). The difference in BMI persisted even after their calorie intakes and total daily physical activity were altered."

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