Poor diets are among the top causes of ill health globally, accounting for nearly one in five deaths, according to a study published on Thursday that called on governments and businesses to do more to improve eating habits.
Eating unhealthy food, or not having enough food - including children unable to breastfeed - contribute to widespread malnutrition, said researchers behind the latest Global Nutrition Report.
The report is an independently produced annual analysis of the state of the world's nutrition.
"Diets are one of the top risk factors of morbidity and mortality in the world - more than air pollution, more than smoking," said Jessica Fanzo, a professor at Johns Hopkins University and a lead author.
"What we're eating is killing us. So something needs to get us back on track with our food system," she said on the sidelines of a global food conference in Thailand's capital, Bangkok.
She said a lack of knowledge and affordability of nutritious food, as well as ineffective supply chains, are among the factors that contribute to poor diets.
The researchers analysed 194 countries and found that malnutrition could cost the world $3.5 trillion per year, while excess weight and obesity could cost US$500 billion annually.
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Every country is battling some form of malnutrition - be it children who are anaemic or too short for their age, or women who are overweight but undernourished because of unhealthy diets - and adolescence obesity rates are rising, the report said.
Most countries are unlikely to meet nine global targets on nutrition that they have signed up to achieve by 2025 including on adult obesity and diabetes, anaemia and child health.
Progress has been "unacceptably slow", the authors warned.
However, there is now better and more detailed data, which has created an unprecedented opportunity to craft effective responses, according to the report.
It cited Amsterdam, which faced a weight crisis among young people and set up programmes in 2012 to prevent and treat obesity, as well as facilitate learning and research on the issue.
Initiatives included public drinking fountains, restrictions on food advertising and guidance for healthy snacks in schools. Today, the prevalence of people who are overweight or obese in Amsterdam is levelling off, the report said.
Reducing food waste could also improve nutrition, said Sir John Beddington, co-chair of the Global Panel on Agriculture and Food Systems for Nutrition, an independent group of experts.
"Each year more than half of all the fruits and vegetables produced globally are lost or wasted," he told the Thomson Reuters Foundation.
Ms Fanzo noted that nutrition is crucial to building up immunity against disease, as well as mental cognition.
"You have to care about what people are eating if you want to build the intellect of your country," she said.