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

The study was published in The Lancet ahead of World Obesity Day (11 October). It analysed weight and height measurements from nearly 130 million people aged over five years (31.5 million people aged five to 19, and 97.4 million aged 20 and older), making it the largest ever number of participants involved in an epidemiological study. More than 1000 contributors participated in the study, which looked at body mass index,BMI, and how obesity has changed worldwide from 1975 to 2016.

Obesity rates in the world’s children and adolescents increased from less than 1 percent (equivalent to five million girls and six million boys) in 1975 to nearly 6 percent in girls (50 million) and nearly 8 percent in boys (74 million) in 2016. Combined, the number of obese five 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, says: "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 remain unacceptably high."

Professor Ezzati adds: "These worrying trends reflect the impact of food marketing and policies across the globe, with healthy nutritious foods too expensive for poor families and communities. The trend predicts a generation of children and adolescents growing up obese and at greater risk of diseases, like diabetes. We need ways to make healthy, nutritious food more available at home and school, especially in poor families and communities, and regulations and taxes to protect children from unhealthy foods."

The authors say that if post-2000 trends continue, global levels of child and adolescent obesity will surpass those for moderately and severely underweight youth from the same age group by 2022. In 2016, the global number of moderately or severely underweight girls and boys was 75 million and 117 million respectively.

Nevertheless, the large number of moderately or severely underweight children and adolescents in 2016 (75 million girls and 117 million boys) still represents a major public health challenge, especially in the poorest parts of the world. This reflects the threat posed by malnutrition in all its forms, with there being underweight and overweight young people living in the same communities.

Children and adolescents have rapidly transitioned from mostly underweight to mostly overweight in many middle-income countries, including in East Asia, Latin America and the Caribbean. The authors say this could reflect an increase in the consumption of energy-dense foods, especially highly processed carbohydrates, which lead to weight gain and poor lifelong health outcomes.

Dr Fiona Bull, programme coordinator for surveillance and population-based prevention of noncommunicable diseases (NCDs) at WHO, says: "These data highlight, remind and reinforce that overweight and obesity is a global health crisis today, and threatens to worsen in coming years unless we start taking drastic action."

In conjunction with the release on the new obesity estimates, WHO is publishing a summary of the Ending Childhood Obesity (ECHO) Implementation Plan. The plan gives countries clear guidance on effective actions to curb childhood and adolescent obesity. WHO has also released guidelines calling on frontline healthcare workers to actively identify and manage children who are overweight or obese.

Dr Bull adds: "WHO encourages countries to implement efforts to address the environments that today are increasing our children’s chance of obesity. Countries should aim particularly to reduce consumption of cheap, ultra-processed, calorie dense, nutrient poor foods. They should also reduce the time children spend on screen-based and sedentary leisure activities by promoting greater participation in physical activity through active recreation and sports."