Exposure to Evening Blue Light Linked to Increased Hunger

Exposure to blue light before and during the evening meal increases hunger and may also alter metabolism, a new study reveals.

Researchers at Northwestern University Chicago found a new technique to alter food intake and metabolism. This new method includes manipulation of exposure to light, mainly blue light.

Researchers conducted a study that included 10 healthy adults with regular sleep and eating schedules. These adults received similar carbohydrate-rich isocaloric meals. As a part of the study the participants had to complete a four day protocol under dim light conditions that involved exposure to less than 20 lux during the 16 hours awake and less than 3 lux during eight hours of sleep.

On the third day, the participants were exposed to three hours of 260 lux, blue-enriched light starting 10.5 hours after waking up. The researchers then compared these effects with exposure to dim light on day two.

The researchers noticed that compared to dim light exposure, the blue-enriched light exposure elevated hunger that started 15 minutes after onset of light and continued even two hours after the consumption of meal.  Apart from this, exposure to blue light was associated with reduced sleep that eventually led to higher measures of insulin resistance.

"It was very interesting to observe that a single three-hour exposure to blue-enriched light in the evening acutely impacted hunger and glucose metabolism," said study co-author Ivy Cheung, at Northwestern University in Chicago, Illinois. "These results are important because they suggest that manipulating environmental light exposure for humans may represent a novel approach of influencing food intake patterns and metabolism."

The researchers suggested further studies to determine the mechanism of action involved in the association of exposure to light with hunger and metabolism.

There are several other benefits of exposure to blue light, a recent study by researchers at Brigham and Women's Hospital found that exposure to short wavelength of blue light enhances alertness and performance during the night. Another study shows that exposure to morning short-wavelength "blue" light has the potential to help sleep-deprived adolescents deal with stress.

The finding was reported in the journal Sleep.