Early Morning Activity and Bright Light Exposure Linked to Lower BMI, Studies Reveal

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A new study published Wednesday in the journal PLOS ONE reveals that those who got more natural light exposure at the beginning of the day were the most likely to have a low body mass index (BMI), the Los Angeles Times reports.

Circadian rhythm, or the 24-hour metabolic oscillation that regulates our physiological processes, plays a key role in regulating our metabolism. Exposure to sunlight in the morning influences both one’s amount of body fat and the hormones that regulate appetite, according to the Los Angeles Times.

This comes in almost direct contrast to reports that light pollution and artificial light from computers and smartphones contribute to not only obesity, but depression and even cancer as well, according to an April 2 grist.org article.

Approximately 150 to 200 million Americans look at a computer screen for more than three hours daily. When a person looks at an artificial light source after dark, the production of melatonin is delayed. According to an article on healio.com, nighttime light exposure can cause an increased risk for afflictions and ailments like sleep disturbances, mood disorders and cognitive impairments as well.

The researchers of the study published in PLOS ONE said the key to using light exposure to lose and keep off weight is to bask in light of at least 500 lux (sunlight emits light at about 120,000 lux at noon on a cloudless day, for comparison), and that such basking is most effective when the light exposure is early in the day. For every hour that light exposure was delayed in the study, average BMI rose by 1.28 points, according to the Los Angeles Times.

“Light is a powerful biological signal and appropriate timing, intensity and duration of exposure may represent a potentially modifiable risk factor for the prevention and management of obesity in modern societies,” the researchers concluded.

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