The World Health Organization has called for a dramatic drop in the consumption of sugar, "hidden" in everything from fizzy drinks and ketchup, as it steps up the fight against obesity.

The UN health agency had previously issued guidelines that sugars should make up less than 10% of a person's total daily energy intake, but have now halved that recommendation to 5%.

Setting the bar at 5% would mean people should consume no more than 25 grammes, or the equivalent of six teaspoons of sugar a day - less than the 10 teaspoons in an average soft drink can.

Health-hazardous free sugars, in the form of table sugar, fructose or glucose for instance, are added to foods and drinks by manufacturers, cooks and consumers themselves, and are naturally present in substances like honey and fruit juices.

The guidelines do not refer to sugars in fresh fruits, vegetables and milk, since there is no evidence they are harmful, WHO said.

The UN agency pointed out that much of the so-called free sugars we consume today are "hidden" in processed foods that are not usually seen as sweet, like ketchup, which contains a full teaspoon of the sugar in each tablespoon.

WHO has recommended keeping sugar consumption below 10% of a person's total daily energy intake for more than a decade - a target it considers clearly supported by scientific evidence which countries should adopt as policy.

But the UN health agency decided to halve the previous recommended level following a year of discussions among WHO member states.

The 5% recommendation however remains "conditional" since too few epidemiological studies have been carried out in populations with such low sugar intake to allow a clear comparison.