The World Health Organization said on Tuesday governments should raise taxes on sugary drinks to fight what it says are global obesity and diabetes epidemics.

If retail prices of sugar-sweetened drinks are increased by 20% through taxation, there is a proportional drop in consumption, it said in a report titled “Fiscal Policies for Diet and Prevention of Noncommunicable Diseases”.

Obesity more than doubled worldwide between 1980 and 2014, with 11% of men and 15% of women classified as obese – more than 500 million people, the WHO said.

An estimated 42 million children under age 5 were overweight or obese in 2015, said Dr. Francesco Branca, director of WHO’s department for nutrition and health. This was an increase of about 11 million over the past 15 years.

Additionally, some 422 million adults across the world have diabetes.

The WHO said there was increasingly clear evidence that taxes and subsidies influence purchasing behavior, and that this could be used to curb consumption of sugar-sweetened drinks and hence fight obesity and diabetes.

“We are now in a place where we can say there is enough evidence and we encourage countries to implement effective tax policy,” Temo Waqanivalu, coordinator at WHO’s department of Noncommunicable Diseases and Health Promotion, told a briefing.

The United States has the world’s highest rates of obesity per population, but China also has similar absolute numbers among both men and women, Branca, the nutrition director, said.

Sweet drinks are also popular in Latin America, where people in Chile and Mexico are the biggest consumers, he said.

WHO guidelines issued in March 2015 said that adults and children from the Americas to Western Europe and the Middle East need to roughly halve the amount of sugar they consume to lower risk of obesity and tooth decay.

The guidelines mean people should reduce the amount to less than 10% of their daily energy intake — or to about 50 grams or 12 teaspoons of sugar for adults – but 5% is even better, it said.

The WHO’s recommendations cover free sugars such as glucose and fructose, and sucrose or table sugar added to processed foods and drinks.