More than half of all adults and a third of children, teenagers and young adults around the world are predicted to be overweight or obese by 2050.

The findings come in a new study of global data published in The Lancet journal, covering more than 200 countries.

Researchers warn that obesity levels are predicted to accelerate rapidly during the remainder of this decade, particularly in lower-income countries.

However, experts say that if governments take urgent action now, there is still time to prevent what they describe as a "profound tragedy".

By 2021, almost half the global adult population - a billion men and 1.11 billion women aged 25 or older - were overweight or obese.

The proportion of both men and women living with these conditions has doubled since 1990.

If trends continue, global rates of overweight and obese adults would rise to about 57.4% for men and 60.3% for women by 2050.

In terms of raw numbers, China (627 million), India (450 million) and the USA (214 million) will be the countries with the biggest populations of overweight or obese people in 2050.

However, population growth means that forecasters are predicting the number in sub-Saharan Africa will rise by more than 250% to 522 million.

Nigeria, in particular, stands out, with the predicted number projected to more than triple - from 36.6 million in 2021 to 141 million in 2050. That would make it the country with the fourth-largest population of adults who are overweight or obese.

The authors acknowledge the study does not take into account the impact that new weight loss medications might have - and they could play a significant role in the future.

Experts say if governments take urgent action now, there is still time to prevent what could be a disaster for vulnerable healthcare systems.

The research was led by Prof Emmanuela Gakidou, from the Institute for Health Metrics and Evaluation (IHME), at the University of Washington in the US.

She said: "[Governments] can use our country specific estimates on the stage, timing, and speed of current and forecasted transitions in weight to identify priority populations experiencing the greatest burdens of obesity who require immediate intervention and treatment, and those that remain predominantly overweight and should be primarily targeted with prevention strategies.

"The unprecedented global epidemic of overweight and obesity is a profound tragedy and a monumental societal failure," she added.

A surge in rates of obesity is happening right now, particularly among young people.

Rates of obesity in children and younger teenagers (from 8.8% to 18.1%) and younger adults (those under 25 - from 9.9% to 20.3%) more than doubled between 1990 and 2021.

However, by 2050 one in three young people will be affected.

The co-lead author of the report, Dr Jessica Kerr of the Murdoch Children's Research Institute in Australia, says the figures present a real challenge to health care systems in the coming years.

"But if we act now, preventing a complete transition to global obesity for children and adolescents is still possible," she said.

"Our estimates identify children and adolescents in much of Europe and south Asia living with overweight who should be targeted with obesity prevention strategies.

"We have also identified large populations, particularly adolescent girls, in North America, Australasia, Oceania, North Africa and the Middle East, and Latin America that are expected to tip over to obesity predominance and require urgent, multifaceted intervention and treatment.

"This is essential to avoid intergenerational transmission of obesity and to prevent a wave of serious health conditions and dire financial and societal costs for future generations."