Many Vietnamese have diabetes but are unaware of it - and the condition is spreading fast in South East Asia, scientists have warned.
A study by Australian and Vietnamese scientists found about 11% of men and 12% of women in Vietnam's Ho Chi Minh City had undiagnosed type 2 diabetes.
This was in addition to the 4% of people who had been diagnosed.
The scientists, from Australia's Garvan Institute of Medical Research, blamed changing lifestyles and fast food.
"Dietary patterns have been changing dramatically in Vietnam in recent years, particularly in the cities as they become more Westernised," said Professor Tuan Nguyen of the Sydney-based institute.
"There are fast food outlets everywhere," he said, adding that similar studies in Thailand reinforced the link.
"Because of that, we feel very confident that we can extrapolate our findings to other parts of South East Asia including Malaysia, Singapore, Cambodia and Laos," he said.
The study was based on a sample of more than 2,000 people.
The condition is caused by high levels of sugar and fat in the diet and inadequate exercise.
The most common form of diabetes can lead to heart disease, vision loss and kidney failure.