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 Obesity is imposing an increasingly heavy burden on the world’s population in rich and poor nations alike, with almost 30 percent of people globally now either obese or overweight – a staggering 2.1 billion in all, researchers said on Wednesday.

The researchers conducted what they called the most comprehensive assessment to date of one of the pressing public health dilemmas of our time, using data covering 188 nations from 1980 to 2013.

Nations in the Middle East and North Africa, Central America and the Pacific and Caribbean islands reached staggeringly high obesity rates, the team at the University of Washington’s Institute for Health Metrics and Evaluation in Seattle reported in the Lancet medical journal.

The biggest obesity rises among women came in Egypt, Saudi Arabia, Oman, Honduras and Bahrain. Among men, it was in New Zealand, Bahrain, Kuwait, Saudi Arabia and the United States.

The richest country, the United States, was home to the biggest chunk of the planet’s obese population – 13 percent – even though it claims less than 5 percent of its people.

Obesity is a complex problem fueled by the availability of cheap, fatty, sugary, salty, high-calorie “junk food” and the rise of sedentary lifestyles. It is a major risk factor for heart disease and stroke, diabetes, arthritis and certain cancers. Chronic complications of weight kill about 3.4 million adults annually, the U.N. World Health Organization says.