Bright morning light can keep the kilos off
Here’s another strategy for managing your weight: get some bright morning light. A new Northwestern study reports the timing, intensity and duration of your light exposure during the day are linked to your weight. People 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, the study found. (BMI is a ratio calculated from a person’s weight and height). The earlier this light exposure occurred during the day, the lower an individuals’ body mass index. The later the hour of moderately bright light exposure, the higher a person’s BMI.
It is worth noting that the influence of morning light exposure on body weight was independent of an individual’s physical-activity level, caloric intake, sleep timing, age or season. Researchers estimate that it accounted for about 20 percent of a person’s BMI. The message is that you should get more bright light between 8 a.m. and noon. About 20 to 30 minutes of morning light is enough to affect BMI. 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.
What’s the magic number for low BMI? Many people do not get enough natural light in the morning because our lifestyle is predominantly focused indoors. We also work in poorly lit environments, usually about 200 to 300 lux of brightness. In the study, 500 lux was “the magic number” or minimum threshold for having a lower BMI. Even on a cloudy day, outdoor light is more than 1,000 lux of brightness. It is difficult to achieve this light level with usual indoor lighting.
Light may be the next frontier for weight loss. Light is a modifiable factor with the potential to be used in weight-management programs. Just like people are trying to get more sleep to help them lose weight, perhaps manipulating light is another way to lose weight. As part of a healthy lifestyle, people should be encouraged to get more appropriate exposure to light. Workplaces and schools should have windows. Employees should be encouraged to go outside for lunch or breaks, and indoor lighting should be improved in the school and workplace. Bottom line, light plays a role in regulating metabolism, hunger and satiety.