Melbourne: Parents, take note! Young children who are exposed to more light earlier in the day tend to weigh more, according to a world-first study.
The study also linked increased light exposure, including light given off by tablets, mobile phones, night lights, and television, to higher risk of obesity in children.
Researchers studied 48 children aged three to five from six Brisbane childcare centres over a two week period, measuring each child's sleep, activity and light exposure along with their height and weight to calculate their body mass index (BMI).
"We found moderate intensity light exposure earlier in the day was associated with increased BMI while children who received their biggest dose of light - outdoors and indoors - in the afternoon were slimmer," said Cassandra Pattinson, a PhD student at Queensland University of Technology in Australia.
"Surprisingly physical activity was not associated with the body mass of the children but sleep timing and light exposure was," Pattinson said.
"This is the first time light has been shown to contribute to weight in children," she said.
"With an estimated 42 million children around the globe under the age of five being classified as overweight or obese, it is a significant breakthrough and a world-first," she said.
"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 parallelled global increases in obesity," she said.
Pattinson said it is known the timing, intensity and duration of exposure to both artificial and natural light have acute biological effects in mammals.
"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 said.
"While adults who take in more morning light are slimmer, pre-school children exposed to morning light tend to be heavier," she said.
"Factors that impact on obesity include calorie intake, decreased physical activity, short sleep duration, and variable sleep timing. Now light can be added to the mix," Pattinson said.
