Weight Loss

Light Impacts Body Weight

It seems we are always tied to some type of device- a phone, computer, tablet, TV, or e-reader. They are a constant part of our lives. There’s no question they have changed how we work, interact, and communicate. New evidence shows they also impact our weight. 

Before the advent of electricity we all awoke to sunshine and slept when it faded into night. Our bodies run on a circadian rhythm. This defines when hormones should be at their highest or their lowest throughout the day for optimal benefit. But when light is introduced, these hormones get disrupted and the balance is impaired. 

By introducing light, especially in the blue and green ranges, our cortisol cycles are disrupted. When exposed to light in the evening hours, cortisol levels surge, interfering with sleep and making us restless. This then diminishes the amount of cortisol we have available in the morning, making us sluggish and tired. Weight is also impacted:

1) The disruption in the normal circadian rhythm of cortisol increases our appetites and encourages late night forays to the refrigerator .
2) Light also impairs melatonin secretion that is imperative to triggering our sleep center and encouraging a healthy sleep cycle. Getting 7-9 hours of sleep every night, regardless of diet or exercise, will produce weight loss. Sleeping the exact same 7-9 hours each night even more weight can be lost.

This creates a vicious cycle and increases already elevated stress levels so more cortisol is produced and cravings for fatty, sugary, high calorie foods are hard to overcome. But cortisol isn’t the only thing affected by light exposure, so is insulin. Artificial light releases not only insulin but raises blood glucose levels as well. Optimally the pancreas is most responsive to insulin in the morning and less so at night while we sleep. That way it is ready and able to more efficiently process all the food, especially carbohydrates, that are consumed throughout the day. Exposure to blue lights in the evening has been shown to increase glucose levels. This results in a build up of glucose in the bloodstream, eventually leading to weight gain and diabetes.

Light exposure has also been linked to possibly causing lower levels of leptin, a hormone that leaves people feeling fuller after eating a meal.

How much is too much?

A mere 8 lux, the equivalent of a tabletop lamp and even a bright nightlight can be enough to disrupt our circadian rhythm. While any type of light can be the culprit, blue light in particular is much more impactful. Wearing glasses that block blue light can help prevent this exposure. Inexpensive orange tinted sunglasses can effectively block the blue light outside, but they are not recommended indoors or at night because they block other colors as well.

So what is the answer?

  • Switch to a red night light. It has less of an impact on our circadian rhythm
  • Stop using devices or bright lights within 2-3 hours of sleep
  • Use blue-blocking glasses, screen cover, or download an app that filters the blue/green wavelength on devices
  • Get a pair of orange tinted sunglasses for during the day
  • Wear blue and green blocking glasses indoors and at night
  • Get up when the sun rises and take multiple breaks throughout the day to bask in the sunlight
  • Use the night shift mode on devices
  • Install a red light in your house, even if it’s just a nightlight

In a weight loss lull? Can’t get past a certain point? Maybe it’s due to something as simple your light exposure. 











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