Northwestern University scientists found that exposure to bright blue light increased insulin resistance during morning and evening exposure. But in the evening, the bright light also caused higher blood sugar levels. Insulin resistance leads to a buildup of blood sugar, which can cause weight gain, higher body fat, and an increased risk for diabetes.
Participants were exposed to blue-enriched light for three hours during the morning or evening. The morning group ate breakfast during that time and the evening group ate dinner. Hunger, sleepiness, and blood levels of glucose, insulin, and other metabolic markers were compared. “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,” said researcher Ivy Cheung. “Our lighting environment impacts our health outcomes.”
A recent Harvard Medical School study found that exposure to blue light in the evening strongly suppresses the secretion of melatonin, the hormone that regulates our circadian rhythms. That disruption appears to raise the risk of obesity. Harvard staff recommends avoiding bright screens at least two hours before bedtime.
“Blue Light Has a Dark Side,” Harvard Health Publications, 9/2/15
“Bright Light Alters Metabolism,” Northwestern University, www.ScienceDaily.com, 5/18/16
“Morning and Evening Blue-Enriched Light Exposure Alters Metabolic Function . . .” by I.N. Cheung et al., PLOS ONE, 5/18/16