Being overweight is so common in Europe that it risks becoming "the new norm", with about a third of teenagers now heavier than is recommended for their health, the World Health Organisation said.
In a report on obesity levels in the 53 countries of the WHO's European region on Monday, the United Nations health agency said up to 27 per cent of 13-year-olds and 33 per cent of 11-year-olds were overweight.
"Our perception of what is normal has shifted; being overweight is now more common than unusual. We must not let another generation grow up with obesity as the new norm," WHO regional director Zsuzsanna Jakab said.
She blamed a "deadly" combination of high levels of physical inactivity, coupled with a culture that promotes cheap, convenient foods high in sugars, fats and salt.
Obesity rates among 11-year-old boys and girls were highest in Greece, Portugal, Ireland and Spain, and lowest in the Netherlands and Switzerland.
Lack of exercise is a key part of the problem. In 23 out of 36 countries, more than 30 per cent of boys and girls aged 15 and over are not getting enough exercise. Among adults, rates of women who do not engage in enough physical activity range from 16 per cent in Greece and 17 per cent in Estonia to 71 per cent in Malta and 76 per cent in Serbia.
The WHO recommends children aged five to 17 should get at least an hour of moderate to vigorous physical activity a day, and adults should do at least two- and-a-half hours of moderate exercise a week.
The report found, however, that some countries, including France and some Scandinavian countries, had managed to contain the obesity epidemic "through a whole-of-government approach".
It said policies such as promoting vegetable and fruit consumption in schools, taxing certain foods to reduce intake and promoting physical activity had helped keep obesity levels stable.