By Phil Mercer
BBC News, Sydney
A survey on obesity has shown that the South Pacific is the world's most overweight region.
Junk food and lack of exercise are largely to blame
The tiny republic of Nauru is the fattest nation on earth. About 94% of its adult population is overweight.
The WHO has warned that poor diet and a lack of exercise increase the risk of illness and premature death.
Doctors say obesity can lead to heart disease and arthritis, and fat children are increasingly being condemned to a lifetime of ill health and disability.
In a list of the world's 10 most overweight countries, eight are in the South Pacific.
Nauru is particularly bad, with almost all of its adult population bulging at the waistline.
The situation in the Federated States of Micronesia, Tonga and the Cook Islands is only slightly better.
According to the World Health Organisation, about 90% of men and women in these isolated corners of the Pacific are obese or overweight.
A change in diet and a lack of exercise are key factors, and Western junk food now has a firm grip on many communities.
A growing number of islanders relies on imported and fatty processed meals - cheap alternatives to fresh fruit and vegetables.
Experts are linking obesity to poverty. Cheap food is often high on calories but low on nutrition.
There can also be cultural barriers when it comes to encouraging people to lose weight, as some groups in the South Pacific believe that beauty is marked by a large physical size.
Obesity is based on body mass index ,which is a measure of weight relative to height. As well as the South Pacific, the United States and Kuwait are also on the unenviable list of the 10 most obese nations.
The WHO has estimated that globally there are 1.6bn overweight adults.
That figure is expected to increase by 40% over the next decade.