Ambient Light Exposure and Weight Gain
The October 2010 Economist reported on findings from Ohio State University linking ambient light exposure to weight gain and poor health in male mice. Previous studies have proven that light plays a part in regulating metabolism; this study looked to discover just how much light it takes to make an impact.
The study looked at three groups of mice. Group one experienced constant low light 24 hours a day, as to resemble a constant overcast day. Group two experienced conditions similar to their natural habitat, 16 hours of overcast daylight followed by 8 hours of darkness. Group three experienced a cycle similar to group two, except the 8-hour darkness was replaced with a dim light as to resemble twilight at dawn break.
After eight weeks, groups one and three had gained 50% more weight than those exposed to the natural light/dark cycle. They also developed glucose intolerance and put on more fat, despite having eaten similar calorie loads and gotten similar amounts of exercise. What differed was when the mice ate. Mice in group two with natural light cycles ate 2/3 of their food in their “daytime” (mice are nocturnal, so their day is when it’s dark; this is their natural time to eat) and 1/3 in their “nighttime” when it was out of whack with their biological clock. The mice in group three, who were constantly exposed to mild light, ate 45% of their food during the “day” and 55% at “night” when it was an unnatural time for them to eat. A follow up experiment found that mice who were fed at a time that was against their natural biological clock gained 10% more than those who were fed when they would eat in the wild as well as those with constant access to food.
The Economist reports much more experimentation needs to occur for us to make assumptions on how this might relate to people. However, nutritionists as well as our mothers have always warned that late night eating leads to weight gain, and this may be some scientific evidence to support the age-old advice. The Economist looks into the future when the complexity of the epidemic of obesity has been unraveled and hypothesizes that we may one day say, it is not just what you eat, but when you eat.
For full article, visit http://www.economist.com/node/17244359