Newly-crowned double Olympic champion Mo Farah said on Sunday that the issue of child hunger had "touched his heart", as he urged political leaders to tackle malnutrition in the poorest parts of the world.
The Somalia-born athlete joined international politicians and sporting greats Pele and Haile Gebrselassie at a "hunger summit" in Downing Street.
Prime Minister David Cameron hopes to secure sufficient commitments from leaders and multinational firms to help prevent 25 million children under five suffering stunted growth by the time of the 2016 Olympic Games in Rio de Janeiro, Brazil.
Mo Farah does the 'mo-bot' outside Number 10
Farah, who has set up his own charity to raise money to help the victims of the severe drought in the Horn of Africa, arrived at Number 10 to cheers after his achievements in winning both the 10,000m and 5,000m.
Speaking at the start of the summit, Farah said: "I'm lucky to have set up a new life here, and growing up here, after being in Somalia as a little boy.
"But there are kids out there facing hunger and starvation and we've got to do something about it.
"There are kids out there who need our help.
"It really touches my heart."
Farah gave a thumbs-up as he arrived at Number 10 before performing the "mobot" - the celebration he displayed after winning both London gold medals.
He later said: "Winning my second gold last night was a dream come true, but I'm here today for perhaps the most important race of all, the race to tackle hunger and malnutrition around the world.
"Last year I visited Somalia during the famine. It was shocking to see people in the country where I was born simply not having enough food to eat. My wife and I came back from Somalia determined to do what we can to help people there rebuild their lives.
"The London Olympics have been an incredible two weeks. And now we have an opportunity to make the legacy of these Olympics one that will inspire generations at home and also one that could save the lives of millions of children, and give them the chance to thrive and to fulfil their potential."
Ahead of the summit, five children ran with Ethiopian distance runner Haile Gebrselassie around the bend of an athletics track in Downing Street, before handing a baton to Mr Cameron as part of a symbolic "race against hunger".
The Prime Minister then joined Farah, Gebrselassie, Brazilian football star Pele and the country's vice-president Michel Temer as they signed the baton to show their support for tackling child hunger.
The summit brought together leaders and senior politicians from Brazil, Kenya, Bangladesh, India and Ireland.
Gebrselassie told the political figures gathered that his home country had been "blighted" by poverty and hunger.
Pointing out that Ethiopia had won three London gold medals, he said: "Just imagine what my country could have achieved if half of our children weren't suffering from malnutrition."
Britain has promised 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.
Another of Team GB's gold medal winners, long jumper Greg Rutherford, is among signatories to an open letter urging Mr Cameron to "fire the starting gun on the biggest ever push against hunger and malnutrition".
Mr Cameron told the summit that both Farah and Gebrselassie were "enormous role models" who would help raise the profile of tackling child hunger.
He later pointed to figures which suggest that one billion people go to bed hungry every night.
Mr Cameron told the summit: "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 the 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 added: "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 to Mr Cameron was also signed by double medal-winning gymnast Louis Smith, judo silver medallist Gemma Gibbons, 10,000m winner Tirunesh Dibaba, from Ethiopia, and five GB Olympians.
It was organised by aid charity Save The Children, which said that on present trends there will be more than three million more stunted children across Africa by the time of the Rio Games.
The athletes told Mr Cameron: "With world leaders gathered in London and the eyes of billions focused on Britain, the Olympics is an incredible opportunity to change the destiny of millions of children round the world.
"As athletes, we know how essential nutritious food is for people to flourish physically and mentally. Despite an abundance of food worldwide, one person in seven goes to bed hungry every night and it is children who are often hit hardest."
They went on: "It doesn't have to be like this. Our world has enough food for everyone. We know how to fix the problem - and we're asking you to rise to the challenge.
"We are delighted that you have shown your commitment by hosting a major hunger event at the Olympics. We're urging you to use that moment to fire the starting gun on the biggest ever push against hunger and malnutrition by committing to put these issues at the top of the UK's G8 presidency next year.
"The eyes of the world are on London 2012. The best legacy the Games can leave is a world where strong, healthy and well-nourished children can achieve their full potential in life."
Tanzanian Frank Kapeta, 15, who is one of the youngsters acting as ambassadors for Save The Children's nutrition campaign, was flown in from Dar Es Salaam for the summit.
He said he had been inspired by watching the Olympics but added that poverty and hunger could thwart his and other youngsters' dreams.
The teenager said: "There is a lot of talented people in Tanzania and the whole of Africa but it's hard to develop these talents and become a hero if you don't get enough food and a variety of nutrients."
Campaign group Baby Milk Action had earlier welcomed the summit but sounded a note of caution about the involvement of the private sector.
It said in a statement: "There are many underlying factors that exacerbate food shortages and hunger, but when public-private partnerships with companies who profit from selling unhealthy products are promoted as the solution there are many risks.
"Partnerships, by their very nature, involve shared decision- making. This can lead to the control of marketing practices that undermine breastfeeding and sustainable, affordable, nutritious family foods being overlooked in favour of voluntary approaches, 'market-led' strategies and corporate-funded education programmes and the double burden of malnutrition - both under- and over-nutrition.
"If governments are serious about finding long-term, sustainable solutions to hunger, it's essential that they address conflicts of interest adequately and protect their health policy planning and implementation processes from undue influence from commercial companies."