Nauru, Tokelau and American Samoa have been listed as the most overweight and obese countries in the world this year.
According to recent World Health Organisation figures, 93.5 percent of the population in each country is overweight and 75 percent in each country is obese.
The study shows Pacific Island countries make up most of the top ten list of the world's fattest countries.
Dr Temo Waqanivaleu from the WHO South Pacific office says Pacific people have become less active and their diets have changed.
"There's much more dependence now on processed foods than the local traditional foods. Not only in terms of choice of foods but in terms of preparations as well. And that has changed a lot. So there's been much dependence now on processed foods than local traditional foods."
Dr Temo Waqanivaleu says processed foods are high in fat, salt and sugar which have led to the high obesity rate and an increase in cases of diabetes and high blood pressure.