More than a billion people are living with obesity around the world, global estimates published in The Lancet show.
This includes about 880 million adults and 159 million children, according to 2022 data.
The highest rates are in Tonga and American Samoa for women and American Samoa and Nauru for men, with some 70-80% of adults living with obesity.
The international team of scientists say there is an urgent need for major changes in how obesity is tackled.
Obesity can increase the risk of developing many serious health conditions, including heart disease, type 2 diabetes and some cancers.
Senior researcher Prof Majid Ezzati, of Imperial College London, told the BBC: “In many of these island nations it comes down to the availability of healthy food versus unhealthy food.
“In some cases there have been aggressive marketing campaigns promoting unhealthy foods, while the cost and availability of healthier food can be more problematic.”
The report, spanning 1990 and 2022, found the rate of obesity quadrupled among children and adolescents. Meanwhile for adults, the rate more than doubled in women and nearly tripled in men.
At the same time, the proportion of adults classed as underweight has fallen by 50%, but researchers emphasise it still remains a pressing problem, particularly among the poorest communities.
World Health Organization (WHO) director general Dr Tedros Adhanom Ghebreyesus said: “This new study highlights the importance of preventing and managing obesity from early life to adulthood, through diet, physical activity, and adequate care.”
He added that it would take the work of governments and communities and “importantly requires the co-operation of the private sector, which must be accountable for the health impacts of their products”.
The network of more than 1,500 researchers, collaborating with the WHO, analysed height and weight measurements from some 220 million people aged five and over.
They used a measure called body mass index.
While they acknowledge this is an imperfect measure of the extent of body fat, and say some countries had better data than others, they argue it is the most widely used, making this global analysis possible.
