New research involving more than 867,000 participants suggests artificial light at night may disrupt circadian rhythms, insulin sensitivity and hunger hormones, increasing the risk of obesity, prediabetes and Type 2 diabetes.
By yourNEWS Media Newsroom
Artificial light at night is emerging as a potential metabolic risk factor, with recent research linking nighttime exposure from streetlights, phones, televisions, digital clocks and other sources to higher rates of obesity, prediabetes and Type 2 diabetes.
A 2026 meta-analysis published in BMC Public Health reviewed 13 studies involving 867,647 participants and found that people exposed to the highest levels of artificial light at night had a 14% higher risk of obesity and a 7% higher risk of being overweight compared with those exposed to the lowest levels.
The findings add to a growing body of research suggesting that the sleep environment may play a larger role in metabolic health than previously recognized. Researchers have identified nighttime light exposure as a factor that can interfere with the body’s circadian clock, which helps regulate sleep, insulin secretion, blood sugar control, fat metabolism and liver function.
A separate study published in The Lancet Regional Health Europe followed 84,790 people using personal light sensors for one week. The study produced 13 million hours of exposure data and followed participants across 670,000 person-years. Researchers from Monash University, Harvard Medical School and the University of Manchester recorded 1,997 new Type 2 diabetes diagnoses during an average follow-up period of 7.9 years.
Participants who slept in the brightest nighttime environments had a substantially higher risk of developing Type 2 diabetes than those who slept in the darkest settings. The study also found that nighttime light exposure and genetic risk operated independently, meaning light exposure was associated with increased diabetes risk regardless of a person’s inherited predisposition.
Researchers concluded that reducing light exposure at night could lower diabetes risk, including among people with a family or genetic risk for the disease.
The biological explanation centers on the body’s internal clock. When artificial light reaches the bedroom during normal sleeping hours, the brain can interpret the signal as extended daylight. That can delay melatonin release, alter cortisol timing and disrupt metabolic processes that depend on a regular 24-hour rhythm.
Insulin sensitivity normally peaks during daylight and declines at night. Artificial light may push glucose metabolism into an extended active period, forcing the body to process signals at a time when it is not designed to do so. Experimental research has found that even one night of sleeping with light exposure can increase insulin resistance the next day in healthy adults.
Northwestern Medicine research published in PNAS found that sleeping in a moderately lit room of 100 lux, compared with a dim room of 3 lux, raised participants’ heart rates and kept the autonomic nervous system activated during sleep. Researchers found that the sympathetic nervous system, which should be less active at night, remained engaged. By morning, participants showed higher insulin resistance.
Nighttime light exposure may also affect appetite regulation. Researchers have found that mistimed light signals can increase ghrelin, the hormone that stimulates hunger, while reducing leptin, the hormone that helps signal fullness. That combination may increase the likelihood of eating at night, when the body is less prepared to process calories efficiently.
Harvard research found that gradually shifting participants’ circadian rhythms through evening light exposure increased blood sugar levels, pushing 10 participants into a prediabetic state. Their leptin levels also declined, weakening the body’s natural fullness signal after meals.
Several studies have linked nighttime light exposure to increased risks of cancer, cardiovascular problems and metabolic disorders, with suppressed melatonin secretion identified as one possible contributor.
Researchers and sleep specialists recommend treating the bedroom as part of metabolic health. Blackout curtains can reduce outdoor light pollution from streetlights and urban glow, which can pass through standard window coverings and disrupt melatonin production.
Experts also recommend removing or covering light sources inside the bedroom, including phone screens, televisions, digital clocks, standby lights and device indicators. Even dim light during sleep has been shown to affect cardiometabolic function by morning.
Northwestern sleep specialist Phyllis Zee has said the color of nighttime light matters. Amber, red or orange light is less stimulating to the brain than white or blue light. When light is necessary, experts recommend keeping it dim, low to the floor and away from the sleeping person. Eye masks and blackout shades may also help when outside light cannot be fully controlled.
The research suggests nighttime light exposure may be an overlooked factor in diabetes prevention. Patients with prediabetes, obesity or fatty liver disease are commonly advised to focus on diet and exercise, while bedroom light exposure is rarely discussed.
The Lancet findings indicate that nighttime light and genetic risk are separate predictors of Type 2 diabetes, suggesting that people with a family history of diabetes may still be able to reduce risk by controlling their sleep environment.
As artificial light pollution expands and obesity rates rise, researchers say reducing bedroom light may be one of the simplest lifestyle changes available to support metabolic health.
Source: Natural News
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