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Here's How to Manipulate Your Metabolism With Light

Nixing blue light after noon is just one way to keep off the pounds.

Researchers from Northwestern University are shedding light (literally) on a new way to keep the pounds off: Optimize when, how much, and what kind of light you're exposing yourself to throughout the day.

In the study, published in the journal PLOS ONE, scientists from Northwestern University randomly exposed 19 healthy adults to three hours of blue-enriched light (the kind that comes from screens like your TV or computer) either half an hour after waking (morning group) or 10.5 hours after waking (evening group) in order to see the effects on hunger, metabolic function, and physiological arousal. The morning group ate breakfast in the blue light, while the evening group ate dinner in the blue light.

The inspiration behind this research comes from past findings from Northwestern scientists who found men and women who receive the majority of their blue light in the morning weigh less than thosee exposed to most of their bright light after 12 p.m. Now we know why.

This new research found that while blue-enriched light exposure both in the morning and evening deeply altered people's metabolisms, causing participants to have a higher insulin resistance (which can lead to Type 2 diabetes later in life), exposure to blue-enriched light in the evening also led to higher peak glucose levels, which makes it increasingly difficult for insulin to stabilize later in the day. Problem is, insulin also happens to be a fat-storing hormone; the more of it you have circulating in your body, the harder it is to burn off fat. 

"Our findings show that insulin was unable to acutely bring glucose levels back to a baseline level following a meal with bright light exposure in the evening," study author Ivy Cheung said in a press release. "The results of this study emphasize that our lighting environment impacts our health outcomes."

The bottom line:
Get natural light first-thing in the morning (before noon). Melatonin—your body's sleep hormone—anticipates darkness, so by getting sunlight in as soon as you wake up, you're able to feel more alert and keep your internal body clock regulated. It also revs your metabolism and primes your body for the day. 

Avoid blue light late in the evenings, as technology (which emits blue-light) can disrupt your circadian rhythm, making it harder to fall asleep, stay asleep, and have restorative sleep. Keep your bedroom technology-free, keep the lights dim, and use dark blinds to keep any external light out to optimize your sleep space. 

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