Study Finds Early Bright Light Linked to Lower BMI

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Last Updated: Dec 12, 2016

If you would like to shed the extra weight, go and bask early in the morning light, according to a research.

In a recent publication on Wednesday in the journal PLOS ONE, people who load up in the morning are more likely to lower their body mass index (BMI). The link between morning light and BMI had nothing to do with the amount of calories that the individuals consumed.

This seems unbelievable but there is scientific evidence to support the association. Researches indicate that circadian rhythm has significant role in regulating metabolism, and exposure to morning light influences body fat and the appetite hormones.

A study found out that for insomniac individuals whose levels of the hormones leptin and ghrelin were high, exposure to morning light for two hours after waking up improved their levels. Another study observed that obese women who were exposed to light between 6 and 9 a.m. in the morning lost some body fat in three weeks. And other studies in animals indicate that if their light exposure is altered, their metabolism changes, causing weight gain without any dietary changes.

Workout In The Morning

Some 54 volunteers were pursued by researchers at Northwestern University’s Feinberg School of Medicine in Chicago. The participants wore wrist monitors that measured their light exposure (including timing and intensity) as well as their sleeping patterns. They were also requested to take note of their diet during the seven-day period.

The participants whose average age was 30 usually slept between 1.26 a.m. and woke up at 8:49 a.m. 58% of them were had a BMI of 24 or lower.

On analyzing their data, the researchers observed a link between their BMI and mean light timing above threshold (MLiT), which is a measurement that accounts for timing, length, and brightness of each participant’s exposure to light.

According to the researchers, the key was to bask in light for a minimum of 500 lux, and that such basking was most valuable when the exposure happened early in the morning. Delaying light exposure for an hour resulted to a BMI increase by 1.28 points.

Important demographic factors such as age and gender, amount of sleep and exercise that the volunteers got, including the season of the year were accounted for in the complete mathematical model.

According to researchers, there were no significant correlations when they limited their analysis to BMI and exposure between 8 a.m. and noon. They thus concluded that light exposure throughout the day assists in regulating body weight.

Early Bright Light Linked to Lower BMI

However, there was something special with the morning light although they are not sure what it could be. But there is a possibility that morning light has a wavelength in the blue portion of the spectrum. The study author wrote that the blue light has strongest effect on the cardiac system.

The researchers concluded that although more studies need to be done, light is a powerful biological signal and with appropriate timing, intensity, and duration of exposure, it could represent a manageable risk factor in the prevention of obesity in the modern world.

Grants from various branches of the National Institute of Health funded the research.

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