A new study says that while adults who take in more morning light are slimmer, pre-school children exposed to more light earlier in day tend to weigh more.
"We found moderate intensity light exposure earlier in the day was associated with increased body mass index (BMI) while children who received their biggest dose of light - outdoors and indoors - in the afternoon were slimmer," said one of the researchers Cassandra Pattinson from Queensland University of Technology in Brisbane, Australia.
"This is the first time light has been shown to contribute to weight in children," Pattinson noted. The researchers studied 48 children aged three to five from six over a two week period, measuring each child's sleep, activity and light exposure along with their height and weight to calculate their BMI.
"Thanks to artificial lighting, including light given off by tablets, mobile phones, night lights, and television, modern children are exposed to more environmental light than any previous generation. This increase in light exposure has paralleled global increases in obesity," Pattinson explained.
"The circadian clock - also known as the internal body clock - is largely driven by our exposure to light and the timing of when that happens. It impacts on sleep patterns, weight gain or loss, hormonal changes and our mood," Pattinson said.
"Recent research in adults suggests exposure to light later in the day is associated with increased body mass, but no studies had investigated these effects in young children and it turns out it has the opposite effect," Pattinson pointed out.
The study was presented at the Australasian Sleep Association's Sleep Downunder Conference in Melbourne, Australia.