Ultra processed foods, include ready meals, biscuits, crisps, burgers and chicken nuggets, instant soups and noodles, ready-made pizzas and pies.
These items are five times more likely to end up on the table in Britain that in Portugal, France or Italy and make up for half of all the meals eaten in the average UK household, making it the unhealthiest nation in Europe, the study suggests.
The study carried out by Professor Carlos Monteiro of the University of Sao Paulo's school of health, compared 19 European countries and concluded that there is a "significant positive association" between eating junk food and obesity.
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"They are also aggressively marketed often in big portion sizes and are typically designed to be consumed as snacks rather than as regular meals. All these factors induce energy over-consumption and thus overweight and obesity," the authors state.
"It's time the UK population woke up to the shocking state of our diet," Professor of Food Policy at City University London, Tim Lang tweeted.
Researchers reviewed data and surveys and reports to estimate the prevalence of obesity in Austria, Belgium, Croatia, Cyprus, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Malta, Norway, Portugal, Slovakia, Spain and the UK.
The information was then compared with the Data Food Networking (DAFNE) and the Living Costs and Food Survey (LCFS) in Britain.
France and Italy had the lowest levels of junk food — ultra processed food — and the lowest prevalence of obesity. Britain, had the highest intake of junk food and more obese people.
"The findings reinforce the need for public policies and actions that promote consumption of unprocessed or minimally processed foods and make ultra-processed foods less available and affordable," the authors write.
The study published in journal Public Health Nutrition calls for junk food to be made less available and affordable.