Morning Light Can Improve Your Health

We love it when science tells us to do things we actually love doing. Today's good news: If you normally spend your mornings cooped up in a car or cubicle, go outside and enjoy some fresh air, because new research has found a very strong link between morning light and body mass index (BMI, which is calculated from your weight and height).

A Northwestern Medicine study released recently, has determined that the timing, intensity, and length of your light exposure during the day all play a role in your weight — the first time this has been shown. They tested 54 participants (average age: 30), measuring their light exposure levels with a wrist monitor and asking them to log their food intake over seven days. Those mostly exposed to even moderately bright light in the morning had much lower BMIs than those who remained inside until later in the day.

The really interesting part: The influence of morning light was independent of how much study participants exercised, how many calories they consumed, how much they slept, their age, or the season. Morning light alone accounted for about 20% of a person's BMI. And only about 20 to 30 minutes of a.m. light exposure could make a big impact, researchers said.

"The message is that you should get more bright light between 8 a.m. and noon," said study senior author Phyllis C. Zee, M.D., a neurology professor and neurologist at Northwestern Memorial Hospital. "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." How exactly light affects body fat requires more research, she said.