The European office of the World Health Organization (WHO) has warned that the coronavirus pandemic could have unforeseen effects - leading to more obesity among children.

A report by the regional WHO office published on Tuesday found that the closures of schools during lockdowns could have negative consequences for the nutrition and physical exercise of children, as they miss school lunches and activities.

"Covid-19 could potentially amplify one of the most worrying trends in the WHO European Region - growing childhood obesity," said Hans Kluge, WHO regional director for Europe.

Kluge said overweight and obesity were linked to life-threatening diseases such as cardiovascular illnesses, diabetes and cancer.

To avoid a negative impact on kids' futures, Kluge called for science-based policies to promote healthy diets and physical activity - such as taxes on sweetened beverages, according to the report.

The study found that almost one in three children between six and nine was overweight in the region, based on a survey of 36 countries.

The situation was worst in Mediterranean countries, although the situation was slowly improving in countries including Greece, Italy, Portugal and Spain.