A three-day United Nations summit opened in Rome on Monday aimed at tackling a "broken" global food system where millions are starving, billions are obese and the planet is suffering.

The food systems summit comes amid growing food insecurity around the world, with UN agencies warning of an increasing number of people suffering from chronic hunger.

"In a world of plenty, it is outrageous that people continue to suffer and die from hunger," UN Secretary-General Antonio Guterres said at the opening of the meeting.

"Global food systems are broken -- and billions of people are paying the price."

More than 780 million people go hungry around the globe, even as nearly one-third of the world's food is wasted or lost, he said.

And while 462 million people are underweight, two billion are overweight or obese, he added.

The summit brings together representatives from the UN's three food agencies headquartered in Rome -- the Food and Agriculture Organization (FAO), the International Fund for Agricultural Development (IFAD) and the World Food Programme (WFP) -- alongside heads of states, government representatives and delegates.

- Radical transformation -

Food systems include all activities related to producing, processing, transporting and consuming food, and making them more sustainable, efficient and equitable is a complex task.

Involving multiple sectors and actors, food systems are affected by varied trends such as urbanisation, climate change, technology and government policy.

Weather shocks, the Covid pandemic and conflicts including the war in Ukraine have helped push the number of people facing hunger up by 122 million since 2019, according to the WFP.

Between 691-783 million people faced hunger last year, with a mid-range of 735 million, WFP estimated in a report earlier this month.

The FAO has said that no less than a "radical transformation in how food is produced, processed, traded and consumed" is required to feed the world's growing population.

Guterres called for at least $500 billion per year to help needy countries scale up long-term financing to invest in higher performing food systems. 

Doing nothing amounts to $12 trillion annually in social and economic costs, according to IFAD.

It compared the needed funds with the "$10 trillion in revenue generated by the global food industry or the $700 billion paid in agricultural subsidies by wealthy countries".

Unsustainable practices in food production, packaging and consumption are also fueling climate change, Guterres said, "generating one-third of all greenhouse gas emissions, using 70 percent of the world's freshwater, and driving biodiversity loss on an epic scale".

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