A glass of fruit juice a day can lead to weight gain in children, study finds

A glass of fruit juice a day could lead to weight gain in children, a study from the University of Toronto has found.

The study analysed data relating to over 50,000 children's body mass index (BMI), finding that an increased intake of fruit juice correlates to weight gain.

A child's BMI increased slightly on the days that they drank fruit juice, even if it was 100 per cent juice without additional additives, the study found.

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The study included Australian data and looked at popular types of juice, including grape, apple and orange.

Children aged under eight were the most impacted by juice.

"Based on the available evidence from prospective cohort studies ... one serving per day of 100 per cent fruit juice was associated with BMI gain among children," the study said.

"Our findings support guidance to limit consumption of fruit juice to prevent intake of excess calories and weight gain."

A BMI is a calculation of a person's body mass.

It is used to measure if a person is a healthy weight for their age and height, according to the Heart Foundation.

While fruit does contain essential vitamins and antioxidants, it contains little fibre in juice form.

Fruit juice also contains high amounts of "liquid calories" through natural sugars.

The experts suggested parents limit their children's consumption of fruit juice, and opt for a piece of fruit instead.