Morning Sun Promotes Weight Loss

Exposing yourself to sunlight in the morning may aid weight loss, new research suggests. Phyllis C Zee, M.D., Benjamin and Virginia T Boshes Professor of Neurology and director of the Northwestern Medicine Sleep and Circadian Rhythms Research Program at Northwestern University Feinberg School of Medicine, and colleagues studied 54 people (26 males, 28 females) with an average age of 30. Participants wore a wrist actigraphy monitor that measured their light exposure and sleep parameters for 7-days in normal-living conditions, and their caloric intake was determined from 7 days of food logs. Results showed that participants who had most of their daily 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 the most potent agent to synchronize your internal body clock that regulates circadian rhythms, which in turn also regulate energy balance,” said Professor Zee. “The message is that you should get more bright light between 8 a.m. and noon. 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.” The authors recommend 20-30 minutes of morning exposure to light of at least 500 lux (outdoor light is more than 1,000 lux even on a cloudy day).