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A new study shows that getting enough natural morning light as part of a healthy lifestyle may help prevent overweight and obesity.

Are you an owl or a lark? When it comes to your sleeping and waking habits, you may be an owl if you sleep late and wake up late, or a lark if you sleep early and wake up early. Whatever your habits are, new studies suggest that synchronizing your internal body clock with light exposure may help you regulate your weight. Research shows that making circadian health an important part of your lifestyle can help prevent obesity, which is now becoming a major health problem all over the world.


People Do Not Get Enough Morning Light

Many people do not get enough natural morning light, partly because of their lifestyles, which includes their jobs and personal habits. Although other people get up early in the morning to go to work or to school, most of them stay indoors in their offices, schools or homes for most of the day. Others stay up late up night, by choice or working night shifts, and wake up later in the day. Could these lifestyle factors influence the current overweight or obesity problem many people have?

Many studies have found that sleeping late and short sleep duration are linked with higher body mass index(BMI, a measure of body fat). These conditions are associated with lower exposure to natural morning light.

Earlier studies show that exposure to morning light influences the amount of body fat and the levels of hormones that regulate appetite.

Other studies also suggest that sleep duration and light exposure may influence metabolic function, body fat, and appetite. One intervention study involving obese women has shown that receiving sunlight in the morning for at least 45 minutes for three weeks reduced appetite and body fat. A similar study comparing the effects of exercise alone versus light exposure and exercise in obese women found that greater reductions in body fat were achieved with the latter intervention. However, there is little evidence that the timing and intensity of exposure to early morning light influences body weight.

Bright Morning Light and Body Weight

Scientists from Northwestern University Feinberg School of Medicine recently published the results of their study, showing that exposure to moderate levels of early morning light can reduce body weight, regardless of one's physical activity level, sleep timing, or calorie intake.

According to senior author Dr. Phyllis C. Zee, light is the most potent factor which synchronizes your internal body clock and regulates the circadian rhythm. This in turn, regulates energy balance, so that one should get more bright light between 8 and 12 in the morning. Getting about 20 - 30 minutes of sunlight is enough to influence BMI. Zee is a professor of Neurology and is the director of the Northwestern Medicine Sleep and Circadian Rhythms Research Program at the University.

Continue reading after recommendations

  • Reid KJ, Santostasi G, Baron KG, Wilson J, Kang J, et al. (2014) Timing and Intensity of Light Correlate with Body Weight in Adults. PLoS ONE 9(4): e92251. doi:10.1371/journal.pone.0092251
  • Northwestern University. "Morning rays keep off pounds." ScienceDaily. ScienceDaily, 2 April 2014.
  • Danilenko KV, Mustafina SV, Pechenkina EA. Bright Light for Weight Loss: Results of a Controlled Crossover Trial. Obes Facts 2013,6:28-38.
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