There has been a ten-fold increase in the number of children and adolescents with obesity since 1975.

Analysis of weight trends in 200 countries has found there was an increase from about 5 million obese girls worldwide in 1975 to 50 million in 2016, and from 6 million to 74 million boys.

Rates of child and adolescent obesity were highest (above 30 per cent) in some islands in Polynesia, and were around 20 per cent or higher in the USA and some countries in the Middle East and North Africa (eg Egypt, Kuwait, Qatar and Saudi Arabia) and the Caribbean (eg Bermuda and Puerto Rico).

Overall, the global prevalence of child and adolescent obesity increased from 0.7 per cent to 5.6 per cent for girls, and from 0.9 per cent to 7.8 per cent for boys.

But despite the significant increase, more children remain moderately or severely underweight than obese worldwide.

There were about 75 million girls moderately or severely underweight in 2016 and 117 million boys.

Almost two thirds of the world’s children and adolescents who are moderately or severely underweight live in south Asia.

“Rates of child and adolescent obesity have increased significantly over the past four decades in most countries in the world,” says study author Dr James Bentham, University of Kent, UK.

“While average BMI among children and adolescents has recently plateaued in Europe and North America, this is not an excuse for complacency as more than 1 in 5 young people in the USA and 1 in 10 in the UK are obese. Additionally, rates of child and adolescent obesity are accelerating in east, south and southeast Asia, and continue to increase in other low and middle-income regions.”

Professor Majid Ezzati, study author from Imperial College London, adds: “While there have been some initiatives led by governments, communities or schools to increase awareness about childhood and adolescent obesity, most high income countries have been reluctant to use taxes and industry regulations to change eating and drinking behaviours to tackle child obesity.”

“Most importantly, very few policies and programmes attempt to make healthy foods such as whole grains and fresh fruits and vegetables affordable to poor families. Unaffordability of healthy food options to the poor can lead to social inequalities in obesity, and limit how much we can reduce its burden.”

The authors also note that policies to prevent child obesity in entire countries and communities need to be matched by improved treatments, such as behavioural therapy to change diet and exercise, screening and management of hypertension and liver problems, and in extreme cases, bariatric surgery.

“The trends show that without serious, concerted action to address obesity, from improving diets and providing the means by which to increase physical activity, to implementing the health system measures required to address overweight and obesity in young people early on, then the health of millions of people will be needlessly placed in great jeopardy, leading to immense human and economic costs to communities,” says researcher Leanne Riley from the WHO.

There is a strong need to deal with both extremes, Prof Ezzati added.

“There is a continued need for policies that enhance food security in low-income countries and households, especially in South Asia,” he said.

“But, our data also show that the transition from underweight to overweight and obesity can happen quickly in an unhealthy nutritional transition, with an increase in nutrient-poor, energy-dense foods.

“Our findings highlight the disconnect between the global dialogue on overweight and obesity, which has largely overlooked the remaining under-nutrition burden, and the initiatives and donors focusing on under-nutrition that have paid little attention to the looming burden of overweight and obesity.”

The study is accessible here.