There's proof regulating children's screen time can reduce the risk of childhood obesity.

An Auckland University study has found cutting young children's device use and ensuring they get enough sleep both lower obesity risk.

Professor Boyd Swinburn says it used data from more than 5,000 children aged between two to four-and-a-half

He says the World Health Organisation recommends pre-schoolers have less than an hour of screentime a day.

"In this cohort, 70 percent of them actually had more than an hour of screen time a day - it is a challenge keeping these young kids from the screens."

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