Morning sunlight could help you lose weight
According to a new study, bright morning light is associated with weight loss. People who had most exposure to 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.
Sunlight and BMI
The results suggested that the earlier in the day light exposure occurred, the lower the BMI.
Many people don’t get enough natural light in the morning. Another concern is that people work in poorly lit offices or environments, usually about 200-300 lux. In the study, 500 lux was the ‘magic number’ 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 normal indoor lighting.
The researchers drew their conclusions by correlating masses of data about people’s BMIs with their lifestyles. What they found was that BMI was associated not just how much light you receive, but also when you get it and for how long.
To explore this further, a study was run with 54 participants (26 males, 28 females), with an average age of 30. The participants wore a wrist actigraphy monitor (a non-invasive method of monitoring human rest/activity cycles) that measured their light exposure and sleep parameters for seven days in normal-living conditions. Their caloric intake was determined from seven days of food logs.
The study showed that the influence of morning light on weight was independent of physical activity, caloric intake, sleep timing, age or season. The researchers argue that the finding emphasizes the importance of “circadian health” in which exposure to light and dark is synchronized with your internal body clock.
The study was carried out by Northwestern medicine and it has been reported to the journal PLOS One, in a paper titled Timing and Intensity of Light Correlate with Body Weight in Adults.