The number of obese children and adolescents (aged 5 to 19 years) worldwide has risen tenfold in the past four decades, according to a new study led by Imperial College London and the World Health Organization (WHO). If current trends continue, more children and adolescents will be obese than moderately or severely underweight by 2022.

The study analysed weight and height measurements from nearly 130 million people aged over five (31.5 million people aged 5 to 19, and 97.4 million aged 20 and older), the largest number of participants ever involved in an epidemiological study. More than 1000 researchers contributed to the research, which looked at body mass index (BMI) and how obesity has changed worldwide from 1975 to 2016.

During this period, obesity rates in the world’s children and adolescents increased from less than 1% (equivalent to five million girls and six million boys) in 1975 to nearly 6% in girls (50 million) and nearly 8% in boys (74 million) in 2016. Combined, the number of obese 5 to 19 year olds rose more than tenfold globally, from 11 million in 1975 to 124 million in 2016. An additional 213 million were overweight in 2016 but fell below the threshold for obesity.

Lead author Professor Majid Ezzati, of Imperial’s School of Public Health, said: “Over the past four decades, obesity rates in children and adolescents have soared globally, and continue to do so in low- and middle-income countries. More recently, they have plateaued in higher income countries, although obesity levels there remain unacceptably high."

The study was published in The Lancet journal.

In 2016, there were 50 million girls and 74 million boys with obesity in the world, while the global number of moderately or severely underweight girls and boys was 75 million and 117 million respectively.

The number of obese adults increased from 100 million in 1975 (69 million women, 31 million men) to 671 million in 2016 (390 million women, 281 million men). Another 1.3 billion adults were overweight, but fell below the threshold for obesity.

The rise in childhood and adolescent obesity in low- and middle-income countries, especially in Asia, has accelerated since 1975. Conversely, the rise in high income countries has slowed and plateaued.

The largest increase in the number of obese children and adolescents was seen in East Asia, the high-income English-speaking region (USA, Canada, Australia, New Zealand, Ireland and the UK), and the Middle East and North Africa.

In 2016, obesity rates were highest overall in Polynesia and Micronesia, at 25.4% in girls and 22.4% in boys, followed by the high-income English-speaking region. Nauru had the highest prevalence of obesity for girls (33.4%), and Cook Islands had the highest for boys (33.3%).

In Europe, girls in Malta and boys in Greece had the highest obesity rates, at 11.3% and 16.7% of the population respectively. Girls and boys in Moldova had the lowest obesity rates, at 3.2% and 5% of the population respectively.

Girls in the UK had the 73rd highest obesity rate in the world (6th in Europe), and boys in the UK had the 84th highest obesity in the world (18th in Europe). Girls in the USA had the 15th highest obesity rate in the world, and boys had the 12th highest obesity in the world.

Among high-income countries, the USA had the highest obesity rates for girls and boys.

The largest rise in BMI of children and adolescents since 1975 was in Polynesia and Micronesia for both sexes, and in central Latin America for girls. The smallest rise in the BMI of children and adolescents during the four decades covered by the study was seen in Eastern Europe.

The country with the biggest rise in BMI for girls was Samoa, which rose by 5.6 kg/m^2, and for boys was the Cook Islands, which rose by 4.4 kg/m^2. India had the highest prevalence of moderately and severely underweight under-19s througho