Oct 23, 2015 01:54 PM EDT By Staff Reporter, UniversityHerald Reporter

Preschoolers who are exposed to more light earlier in the day tend to weigh more, according to a recent study.

"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," Cassandra Pattinson of Queensland University of Technology said in a statement.

For the study, researchers collected and analyzed data from 48 children between the ages of 3 and 5 from six Brisbane childcare centers over a two week period, Medical Xpress reported. They measured each child's sleep, activity and light exposure along with their height and weight to calculate their body mass index (BMI).

"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," Pattinson 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."

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," she 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 the next step was to figure out how the research can be used in the fight against obesity in children.

The findings will be presented at the ASA Sleep Downunder Conference in Melbourne today.

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