Leading child health and obesity experts say a tax on sugary drinks should be a top-priority in tackling New Zealand's growing waistline

A University of Auckland paper finds that compared to sugar in solid food, sugar in drinks carries a greater risk of chronic illnesses like obesity and diabetes.

It's because of the higher concentration and speed that dissolved sugar is metabolised.

Co-author, Dr Gerhard Sundborn says it therefore makes sense to ban sugar in drinks first, because it's more harmful.

He says sugar in drinks contributes about a quarter of the sugar in the diets of children.