Almost every third person worldwide is overweight or obese, and rates are rising among children, according to research published Monday.

The prevalence of obesity has doubled since 1980 in more than 70 countries and risen in most other countries, according to the study in the New England Journal of Medicine which covered 195 countries from 1980 to 2015.

In 2015, excess weight affected 2.2 billion children and adults. Roughly 700 million of that number, including almost 108 million children, were obese.

"Excess body weight is one of the most challenging public health problems of our time, affecting nearly one in every three people," said lead author, Ashkan Afshin, of the Institute for Health Metrics and Evaluation (IHME) in Seattle, U.S.

Among the world's 20 most populous countries, the U.S. had the highest level of obesity among children and young adults at nearly 13 per cent; while Egypt topped the adult obesity list at about 35 per cent.

The global obesity average was 5 per cent among children and 12 per cent among adults.

Bangladesh and Vietnam had the lowest portion at roughly 1 per cent in each respective category.

Another finding was that 4 million people died in 2015 due to illnesses linked to excess weight or obesity. Cardiovascular disease accounted for two thirds, followed by diabetes, kidney disease and cancer.

Obesity was defined as a body mass index (BMI) exceeding 30. The index is based on individuals' height and weight. "Overweight" was a BMI between 25 and 30.

The study was released at a conference in the Swedish capital, Stockholm.