Being overweight is in danger of becoming the new norm for children as well as adults in Europe, the World Health Organisation warns, issuing figures showing that up to a third of 11-year-olds across the region are too heavy.

According to the EU figures, Greece has the highest proportion of overweight 11-year-olds (33%), followed by Portugal (32%), Ireland and Spain (both 30%).

While the UK's figures are not directly comparable, data from the childhood measurement programme in 2011/12 suggests England has as serious a problem as any country, with 35.4% of 10- to 11-year-old boys and 32.4% of girls overweight. Among those, 20.7% of boys and 17.7% of girls were obese.

The school-based measurements also show that 23.5% of four- to five-year-old boys and 21.6% of girls are overweight.

The WHO said the figures for children were alarming. "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," said the WHO regional director for Europe, Zsuzsanna Jakab. "Physical inactivity – coupled with a culture that promotes cheap, convenient foods high in fats, salt and sugars – is deadly."

The WHO's European regional office issued a series of country profiles at the opening event in Athens of the Greek presidency of the EU. The UK profile based on WHO data shows that 64.2% of the adult population were overweight in 2008, among whom 26.9% were obese.

By 2030, it is forecast that more than a third of the population – 36% of men and 33% of women – will be obese. Only the Czech Republic and Malta currently have a higher proportion of overweight adults, according to the WHO data.

Children in Europe are not physically active enough, the WHO says. In 23 out of 36 countries, more than 30% of boys and girls aged 15 or over are not getting enough exercise and eating the wrong sorts of foods.

"We need to create environments where physical activity is encouraged and the healthy food choice is the default choice, regardless of social group," said João Breda, programme manager for nutrition, physical activity and obesity at the European regional office. "Physical activity and healthy food choices should be taken very seriously in all environments – schools, hospitals, cities, towns and workplaces. As well as the food industry, the urban planning sector can make a difference."

UK data shows that saturated fat makes up 12.7% of the calories in an average adult diet, which is higher than the WHO recommended limit of 10%. The fruit and vegetable intake was only just below the recommended 600 grams per day, at 588g.

The UK does extremely poorly by comparison with the rest of Europe on breastfeeding. Only 1% of babies were breastfed by the age of six months as the WHO recommends, in 2010.

WHO Europe condemned the marketing of junk food to children last year in a hard-hitting report. It said children were being surrounded by adverts for foods high in salt, sugar and saturated fat, even in schools and sports centres. The report expressed concern about the use by food marketers of computer games and smartphone apps that children readily access.

Some countries have managed to contain the epidemic, says the WHO, although they have not succeeded in turning it around. In France and some Scandinavian countries, the figures appear to show a plateau effect. The WHO says they have implemented the policies it advises, including promoting the eating of fruit and vegetables in schools, improving the nutritional quality of school lunches, controlling advertising and imposing taxes on some foods, alongside initiatives to encourage more physical activity in children.