Proof regulating children's screen time - can reduce the risk of childhood obesity

An Auckland University study has found rules cut young children's device use and ensure they get enough sleep - and both lower obesity risk.

Professor Boyd Swinburn says it used data from more than five thousand two-to-four-and-a-half-year-olds.

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

Swinburn says almost 70 percent of kids in the study were on screens longer than that.