Babies and children who have been stunted for lack of food are also in danger of obesity in poor countries, as junk food and sugary drinks reach every corner of the globe.

Experts warn of a double burden of malnutrition, with underweight and obese children living in the same communities and even within the same families. One in three low and middle-income countries are now affected, according to experts led by the World Health Organization.

The root of both problems is the same – a dearth of nutritious food. Some children have too little to eat; others have too many empty calories. The high fat, salt and sugar junk snacks of affluent countries are now available in almost every village worldwide and are becoming part of the staple diet of some of the poorest families.

A series of papers in the Lancet medical journal by experts including the WHO says more than a third of low- and middle-income countries are now affected by the double burden of malnutrition. The authors call for action to improve the food supply and protect children’s health.

'Failing' food system leaves millions of children malnourished or overweight Read more

“We are facing a new nutrition reality,” said the lead author of the report, Dr Francesco Branca, director of WHO’s department of nutrition for health and development. “We can no longer characterise countries as low-income and undernourished, or high-income and only concerned with obesity.

“All forms of malnutrition have a common denominator – food systems that fail to provide all people with healthy, safe, affordable, and sustainable diets. Changing this will require action across food systems – from production and processing, through trade and distribution, pricing, marketing, and labelling, to consumption and waste. All relevant policies and investments must be radically re-examined.”

Barry Popkin, professor of nutrition at the University of North Carolina at Chapel Hill School of Public Health, said that three decades ago, middle-income countries had both overweight and stunting. Now it was in the lowest income countries, including sub-Saharan Africa and south and east Asia. Obesity, he said, was now universal – no country was exempt.

“The food system now that is affecting overweight and obesity is also directly affecting under-nutrition,” he said. “Every day at least a third of infants are getting junk food and beverages – ultra-processed foods as we call them today – so that you are starting to see common causes of both. Poor weaning foods and even good weaning foods are being replaced by junk food.”

The drive to feed underweight children has inadvertently contributed to the problem, say the experts. Strategies have focused on getting more calories into hungry children, without ensuring that they grow up eating and getting a taste for the right sort of food. Stunted children who gain weight rapidly may lay down abdominal fat which will predispose them to obesity-related diseases in later life, such as type 2 diabetes, heart attacks and strokes.

Among many well-meaning interventions that may now look unfortunate was fortifying sugar in Guatemala with vitamin A, manufacturing sweet cookies filled with micronutrients for children in India and giving cash for food to Mexican families, which was spent on high fat, salt and sugar products, resulting in overweight and obesity among mothers.

“There was such a concern and a pre-occupation among policymakers with preventing hunger and food insecurity that obesity was just seen as a luxury and wasn’t seen as a health concern,” said Corinna Hawkes, professor of food policy at City, University of London, and author of one of the papers. “In the new nutrition reality, it is not on to ignore it.”

Under-nutrition is an awful problem, she said, but it was irresponsible to think you could fix it and sort out obesity afterwards. More information was needed also for families. Women were taught what to feed their babies, for instance, but not what foods they should avoid. “You get mums and others feeding children seeing all these glamorous snack foods on the market and thinking that’s good for my child,” she said.

Branca said one in three families with a stunted child also had an overweight mother. “It is a paradox. We are seeing that vitamin and mineral deficiency is more and more a constant despite our best efforts to address them with many different programmes with supplementation, with fortification of food – and the common element is clearly the poor quality of food.”

The WHO and the authors are calling on governments, NGOs and all other players to work together to transform the food system. “Without a profound food system transformation, the economic, social, and environmental costs of inaction will hinder the growth and development of individuals and societies for decades to come,” said Branca.