Why Sunshine and Early Bedtime Are Good for Your Child's Metabolism

Research shows that light is good during the day and bad at night

Child sleeping
For optimal family health, make sure you and your kids get plenty of sunshine in the daytime and have an early bedtime. Adriana Varela Photography/Getty Images

You know that old saying about "early to bed and early to rise" making one healthy, wealthy, and wise? It turns out that there's increasing evidence to back up the "healthy" part of this old adage.

What the Research Suggests

A growing body of research is showing evidence that patterns of exposure to light over time is linked to body weight, eating habits, and metabolism. More specifically, some studies have suggested that exposure to bright light later in the day may be associated with higher BMI, or body mass index, and that getting too much light at night and not getting enough light during the day can mess with your metabolism.


A May 2016 study by scientists at Northwestern found that exposure to bright light in the morning and evening increased insulin resistance, the body's inability to effectively move glucose out of the bloodstream. Bright light in the evening caused higher blood sugar levels, indicating that insulin is less able to compensate for the increase in glucose in the evening. Insulin resistance leads to a buildup of blood sugar which, over time, can lead to increased weight gain and body fat and a greater risk for diabetes. In comparison, exposure to dim light did not cause such changes.

"Previous research had shown a link between bright light exposure later in the day and higher BMI," says Kathryn Reid, senior study author and a research associate professor of neurology at Northwestern University Feinberg School of Medicine. "We wanted to know why this is the case."

The researchers studied 19 healthy adults, exposing them to dim light and bright light.

Some participants were exposed to 3 hours of blue-enriched light 30 minutes after waking (morning group) while others were exposed to blue-enriched light 10 1/2 hours after waking (evening group). When each person's dim light exposure and bright light exposure results were compared, the results clearly showed that bright light exposure in the evening resulted in higher peak glucose.

Further studies will need to be done to understand exactly why this happens but the results were clear: Light exposure in the evening elevated glucose. "These results provide further evidence that bright light exposure may influence metabolism," said Kathryn Reid, PhD, senior study author and a research associate professor of neurology at Northwestern University Feinberg School of Medicine.

In addition to limiting too much light in the evening, it's also a good idea to get lots of sunshine in the daytime. Another Northwestern study published in the Journal of Clinical Sleep Medicine showed that office workers with windows at the workplace had more exposure to light during work hours, which was associated with greater physical activity and better sleep.

How to Maximize Light in the Day and Minimize It at Night

  • Get to bed early: Knowing that going to bed is healthy is one thing. Doing it is another. It can be especially difficult to get kids to bed—and yourself as well—in today's TV binge-watching, texting, and social networking world. Turn off the TV at least a couple of hours before bedtime (or better yet, limit TV to weekends) and step away from the computer (because checking your Facebook page isn't that essential, and your child doesn't need to Snapchat or Instagram every evening). And if you are going to binge-watch, limit yourself so that you're not up into the wee hours of the night (something many parents can say they've done more often than they'd care to admit). And steer clear of sneaky sources of caffeine and other things that can interfere with a good night's sleep.
  • Establish good bedtime routines: Setting up good bedtime routines like playing some soft music or doing some stretches is an excellent way for you and your child to mentally and physically relax and prepare for a good night's sleep.
  • Dim the lights for story time: Use a bedside lamp with a dimmer to read a book before bed, whether you're still reading to your child or your child is old enough to read a book on her own with you by her side.
  • Don't use an e-reader or electronic screen before bed: Electronic readers shine the light into your eyes, so paper books are a better choice for bedtime.
  • Get plenty of sunshine during the day: Take your child to the park after school or ask your caregiver to do it so that your child gets some exercise and sunlight before he settles down to do homework. If your workplace doesn't have windows, be sure to get outside during breaks and lunchtime. On weekends, spend as much time outdoors as possible with your family.

    Continue Reading