Circadian rhythm is the body's physical, mental and behavioral changes that follow a roughly 24-hour cycle.
Researchers from the Northwestern University Feinberg School of Medicine found that exposure to morning light from 8 a.m. to noon helps in lowering the body mass index (BMI).
They recruited adults, age 18 and above, and recorded their weight for later comparison, They were then provided with seven days of diet and sleep logs, and a wrist actigraph to be worn outside their clothing on the non-dominant wrist. In the diet logs, participants were instructed to list the quantity and specific description of the food they ate or drink. In the sleep logs, on the other hand, participants were instructed to report their sleeping and waking hours, and sleep duration determined by the actigraph. Light levels were also recorded in the wrist actigraph.
After comparison of the results, they found that individuals who get frequently exposed to morning light had lower BMI compared to those who got exposed in the sunlight later in the day. They also found that the influence of morning sunlight exposure on body weight is not connected to the individual's physical activities, caloric intake, and sleep timing.
"Light is a modifiable factor with the potential to be used in weight management programs," said co-lead author Kathryn Reid, research associate professor of neurology at Northwestern University Feinberg School of Medicine, in a press release. "Just like people are trying to get more sleep to help them lose weight, perhaps manipulating light is another way to lose weight."
When an individual is exposed to the morning sunlight, his body's internal body clock gets synchronized, which in turn, regulates the normal processes in his body. If an individual does not get enough light exposure the perfect timing in the day, on the other hand, his internal body clock will get uncoordinated which can lead to altered metabolism and weight gain.
To achieve a healthy lifestyle, the researchers encourage people to get more appropriate exposure to morning sunlight. They recommend schools and workplaces to have sufficient windows.
Further details of this study can be read in the April 2 issue of PLOS One.
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