Looking for an easy way to lose weight? Study shows exposure to bright light linked to significantly lower BMI

Wanna lose a few pounds? Get yourself out of bed as early as possible and bathe in the morning light for 20 to 30 minutes. Sure, you’re thinking, another ridiculous weight loss tip! But this one, believe it or not, is backed by science.

A new study from Northwestern University finds that the timing, intensity, and duration of your daily light exposure is linked to your weight. In fact, the researchers discovered that participants who had most of their exposure to even moderately bright light in the morning had a significantly lower body mass index (BMI) than those who had most of their light exposure later in the day. “Light is a powerful biological signal and appropriate timing, intensity and duration of exposure may represent a potentially modifiable risk factor for the prevention and management of obesity in modern societies,” wrote the authors in the conclusion of their study.

The study
Participants in the study -26 men and 28 women, with an average age of 30- were asked to log their mealtimes and sleep times and were asked to wear a wrist device that monitored their movements.
Those who were exposed to daily light above 500 lux in the early part of the day had lower BMIs.
Room light is between 150-500 lux while outdoor light is more than 1,000 lux, even on cloudy days.
“The earlier this light exposure occurred during the day, the lower the individuals’ body mass index,” wrote co-lead author Dr. Kathryn Reid. “The later the hour of moderately bright light exposure, the higher a person’s BMI.”

Significantly, the influence of morning light exposure on body weight was independent of a participant's physical activity level, calorie intake, sleep timing, age, or season. Plus, it accounted for about 20% of a person's BMI. “Our results suggest that the relationship between light and BMI is not simply a function of the accumulated minutes of light during the day, but more importantly the temporal pattern of light exposure above a biological threshold,” the authors wrote. 

Our internal body clock
“Light is the most potent agent to synchronize your internal body clock that regulates circadian rhythms, which in turn also regulate energy balance,” explained Phyllis C. Zee, M.D., director of the Sleep and Circadian Rhythms Research Program at Northwestern. “If a person doesn’t get sufficient light at the appropriate time of day, it could de-synchronize your internal body clock, which is known to alter metabolism and can lead to weight gain.”
According to Zee, the crucial hours we should be aiming to see bright light are between eight 8am and midday. No need to overdo it though; about 20 to 30 minutes of this early light is enough to affect BMI.

It isn’t just people who get up late who are at risk of upsetting their metabolism. The fact that most of us work indoors in poorly lit environments also contributes to the problem. The results of the study showed 500 lux to be "the magic number"  in lowering BMI. This is about 200 to 300 lux higher than the artificial lighting provided in an average office.

Bottom line
The researchers believe that their findings could lead to a break-through in approaches to weight management, with the manipulation of light providing a whole new avenue in the treatment of obesity. In addition, lifestyle changes such as taking lunch breaks outside (weather permitting), could help get society in shape.  Zee suggests that we should cultivate a good relationship with our body clocks from a young age, and is convinced that improved lighting and outdoor breaks in schools could “prevent obesity on a larger scale”.

Sources: http://www.eurekalert.org/, http://www.medicaldaily.com/, http://www.independent.co.uk/, http://www.dailymail.co.uk/