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Light Exposure Linked to Weight Gain in Children

Pre-schoolers exposed to more light earlier in the day tend to weigh more, according to research presented to the Sleep Downunder Conference in Melbourne.

Early childhood researchers at Queensland University of Technology studied 48 children aged 3–5 years over a 2-week period, measuring each child’s sleep, activity and light exposure along with their height and weight.

“We found moderate intensity light exposure earlier in the day was associated with increased body mass index, while children who received their biggest dose of light – outdoors and indoors – in the afternoon were slimmer,” said PhD student Cassandra Pattinson.

“Surprisingly, physical activity was not associated with the body mass of the children, but sleep timing and light exposure was. This is the first time light has been shown to contribute to weight in children.

“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.

“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 said that the timing, intensity and duration of exposure to both artificial and natural light have acute biological effects in mammals. “The circadian 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.

“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. While adults who take in more morning light are slimmer, pre-school children exposed to morning light tend to be heavier.

“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.”