The poorest countries in the world are in the grips of an obesity epidemic thanks to the soaring consumption of junk food, according to a major report.

Scientists found at least a fifth of the adult population of every low-income nation is now obese or overweight.

Easy access to cheap high-calorie snacks has fuelled the crisis, with junk food now found in 'every nook and cranny' of the world.

Modern transport has also played a role by slashing activity, while the rise in the number of women moving into the workplace has led to a surge in demand for food that is ready to eat.

It has meant even in sub-Saharan Africa, where the average wage is £4 a day, millions of adults' health is at risk because they are severely overweight.

Obesity was once thought to be exclusively a problem for wealthy countries, fuelled by high wages and sedentary lifestyles.

Scientists found at least a fifth of the adult population of every low-income nation is now obese or overweight

Forcing restaurants to put nutritional labelling on their menus slashes the amount of calories customers eat (file image)

But the new study shows obesity - which triggers a slew of diseases including type 2 diabetes, heart disease and even cancer - is plaguing every corner of the world.

Researchers from the University of North Carolina and the World Health Organisation (WHO) looked at 126 of the most impoverished nations.

There are an estimated 150million children with stunted growth in regions where people are too poor to afford food, according to the report published in The Lancet.

But being overweight was more common than being underweight in poor areas of most countries in Latin America, the Caribbean, eastern Europe and Asia.

Forty-eight of the poorest countries, more than a third, had problems with both malnutrition and obesity, the study found.

Fast-food restaurants have cropped up in even the most isolated of countries around the world.

WHAT IS OBESITY? AND WHAT ARE ITS HEALTH RISKS? An adult is obese if they have a BMI - body mass index - over 30. A healthy person's BMI - calculated by dividing weight in lbs by height in inches, and the answer by the height again - is between 18.5 and 24.9. The US is in the midst of an obesity epidemic, and more than a third of adults are considered obese. Two thirds are overweight or obese, meaning they have BMIs over 25. Another one in five children are obese as well. In total, obesity is estimated to cost the US $149 in medical expenses each year. Half of that is paid for through the publicly-funded healthcare programs, Medicaid and Medicare. Around 35 percent of men and over 40 percent of women in the US are obese, raising their risks of a broad range of chronic diseases and death itself. Such conditions include type 2 diabetes, which can cause kidney disease, blindness and even limb amputations. Diabetes costs the US $327 billion a year, and accounts for one in every $7 spent on health care. Obesity also raises the risk of heart disease, the number one cause of death in the US, responsible for one in every four deaths. Carrying dangerous amounts of weight has also been linked to 13 different cancers: Cancer of the lining of the uterus

Esophageal cancer

Stomach cancer

Liver cancer

Kidney cancer

Multiple myeloma

Meningioma

Pancreatic cancer

Colorectal cancer

Ovarian cancer

Thyroid cancer

Gallbladder cancer

Breast cancer It is suspected that the chronic inflammation associated with obesity damages DNA which, in turn can be carcinogenic. Advertisement

Meanwhile, convenience food like ready meals and snacks laden in sugar and fat are being increasingly exported from the West to impoverished nations.

Lead study author Barry Popkin, professor of nutrition at the University of North Carolina, said: 'We see this in sub-Saharan Africa, we see it in South Asia, the modern junk food system has reached every nook and cranny.

'Our research shows that overweight and obesity levels of at least 20 per cent among adults are found in all low- income countries.

'Reductions in physical activity and rising sales of food rich in refined carbohydrates, fat, sugar and salt were largely to blame.

'I could take you to the middle of the Congo, one of the world's most isolated regions, and I'd be able to show you junk food.'

The researchers used survey data from low- and middle-income countries in the 1990s and 2010s to estimate which countries had problems with both malnutrition and obesity.

The nations fell into this bracket if more than 30 per cent of their population had stunted growth, over 20 per cent of women were too thin, and more than a fifth were overweight.

In the 2010s, 14 of the poorest countries had developed this double burden of nutrition, compared with the 1990s.

However, fewer countries with middle and high incomes were affected than in the 1990s.

The authors say that this reflects the increasing prevalence of being overweight in the poorest countries, where populations still face malnutrition.

Professor Popkin added: 'Emerging malnutrition issues are a stark indicator of the people who are not protected from the factors that drive poor diets.

'The poorest low- and middle-income countries are seeing a rapid transformation in the way people eat, drink, and move at work, home, in transport and in leisure.

'The new nutrition reality is driven by changes to the food system, which have increased availability of ultra-processed foods that are linked to increased weight gain, while also adversely affecting infant and pre-schooler diets.

'These changes include disappearing fresh food markets, increasing supermarkets, and the control of the food chain by supermarkets, and global food, catering and agriculture companies in many countries.'

The report, which estimates that 2.3billion people across the world are obese, said that obesity in China had been sparked by a 'massive reduction in physical activity'.

Researchers blamed sedentary jobs, modern transport and an increase in the number of women getting work.

Mothers are now choosing to buy processed food that is ready to eat or can be heated up in a microwave, the report said.

Co-study author Dr Francesco Branca, director of the Department of Nutrition for Health and Development at WHO, said: 'We are facing a new nutrition reality.

'We can no longer characterize 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.'

A separate study in The Lancet warned schemes set up to tackle hunger in low income countries were now at risk of making nutrition standards worse.

Researchers from the City, University of London said that supplying rice, sugar and cooking oil to poor families in Egypt had caused obesity levels to rise.