Olympic champions Greg Rutherford and Tirunesh Dibaba are spearheading athletes' calls for Britain to use the success of the London Games to push forward action to tackle child malnutrition in poor countries.
The Great Britain and Ethiopian gold medal winners are among several high-profile sporting signatories to an open letter to David Cameron ahead of the "hunger summit" at Downing Street.
In it they urge the Prime Minister to "fire the starting gun on the biggest ever push against hunger and malnutrition" by making it the top priority for the UK's presidency of the G8 next year.
The summit is bringing together leaders and senior politicians from Brazil, Kenya, Bangladesh, India and Ireland as well as sporting greats such as Ethiopian distance runner Haile Gebrselassie and football star Pele.
Britain will promise a £120 million investment in drought-resistant crop research, help for schemes such as a text message hunger alert system in Kenya and pressure on multinational firms to play their part.
Mr Cameron hopes to secure sufficient commitments from other countries and private sector attendees to help prevent 25 million children under five suffering stunted growth by the time of the 2016 Games in Brazil.
The event will begin with youngsters, including a Tanzanian boy who has suffered malnutrition, racing up a running track to the front door of Number 10 to deliver a plea for help.
Speaking at the opening of the summit, Mr Cameron is expected to say: "While people around the planet have been enjoying and competing in these Games there's another world where children don't have enough to eat, and never get the start in life they deserve. It is a tragedy for them, and it's a tragedy for their societies they live in. Children who could grow up to become doctors, farmers, engineers and entrepreneurs or great Olympians are left far behind.
"We've a responsibility to tackle this. But the hard truth is that while we've made huge strides in the last decade on things like education, malnutrition rates have stagnated. I'm determined that Britain helps change this." He will add: "We've just seen in the Olympics what the world can do when it puts its mind to a task. We've got political leaders and great Olympians here. We can't turn away from this and we won't."
The joint letter, also signed by double medal-winning gymnast Louis Smith, judo silver medallist Gemma Gibbons, Gebrselassie and five current and former GB Olympians, was organised by aid charity Save the Children. It said that on present trends there will be more than three million more stunted children across Africa by the time of the Rio Games.