Nearly 60 per cent of all adults and a third of all children in the world will be overweight or obese by 2050 unless governments take action, a large new study said on Tuesday.

The research published in the Lancet medical journal used data from 204 countries to paint a grim picture of what it described as one of the great health challenges of the century.

"The unprecedented global epidemic of overweight and obesity is a profound tragedy and a monumental societal failure," lead author Emmanuela Gakidou, from the US-based Institute for Health Metrics and Evaluation (IHME), said in a statement.

The number of overweight or obese people worldwide rose from 929 million in 1990 to 2.6 billion in 2021, the study found.

Without a serious change, the researchers estimate that 3.8 billion adults will be overweight or obese in 15 years - or around 60 per cent of the global adult population in 2050.

The world's health systems will come under crippling pressure, the researchers warned, with around a quarter of the world's obese expected to be aged over 65 by that time.

They also predicted a 121-per cent increase in obesity among children and adolescents around the world.

A third of all obese young people will be living in two regions - North Africa and the Middle East, and Latin America and the Caribbean - by 2050, the researchers warned.

But it is not too late to act, said study co-author Jessica Kerr from Murdoch Children's Research Institute in Australia.

"Much stronger political commitment is needed to transform diets within sustainable global food systems," she said.

That commitment was also needed for strategies "that improve people's nutrition, physical activity and living environments, whether it's too much processed food or not enough parks," Kerr said.

More than half the world's overweight or obese adults already live in just eight countries - China, India, the United States, Brazil, Russia, Mexico, Indonesia and Egypt, the study said.

The research is based on figures from the Global Burden of Disease study from the IHME, which brings together thousands of researchers across the world and is funded by the Bill and Melinda Gates Foundation. (AFP)