` There is not one country on the planet which has smashed it,” Jamie Oliver says. “Not one country where obesity levels are coming down.”

He has pushed back the sleeves of his blue-and-white striped jumper and gestures not just with his hands but with his whole body - he leans forward, pulls back, stretches his arms along the rustic wooden table. The celebrity chef and school meals campaigner is the first to admit he’s not big on intellectual details. But on this, he is right.

Academics don’t use Oliver’s language but they say the same thing. Professors at Imperial College London and Harvard University in the US published a joint study in The Lancet looking at 199 countries over 28 years. They found that obesity rates went up for men in all but eight of these countries and for women in all but 19.

No studies have been carried out looking at children, however, despite childhood obesity being one of the most serious public health challenges of the 21st century, according to the World Health Organisation. Its warnings are peppered with words such as “alarming” and “premature death”.

Crucially, however, the WHO uses another word too: “preventable”. But for this to happen, Oliver says, we must be prepared to work together and take action on many fronts - in the supermarket, in the workplace, in schools and in homes.

When I meet Oliver, he wants to talk about Australia, from where he has just returned and where about a quarter of adults are now obese. He has formed a partnership with Woolworths, the largest supermarket chain in the country, and a charity, the Good Foundation, and has attracted government funding to set up community kitchens to teach basic cooking.

“In the next three years, Australia is going to show the rest of the world how to do it,” Oliver says with confidence. “Because the only thing that will make a change is lots of changes. Governments say, `What is the one thing we can do?’ But if you think `one thing’, you’re always going to lose, nothing will be achieved.”

Oliver himself has never been known to do just one thing. His near decade-old campaign for better school dinners in the UK has expanded into a worldwide movement to educate children about food. Branded the “Food Revolution” in the US, this work was kick-started in 2010 by a $100,000 prize from TED, the not-for-profit online “ideas network” so beloved of the world’s public intellectuals.

In his TED prize speech, Oliver told the audience about some of the people he met when filming the television show Jamie Oliver’s Food Revolution in Huntington, West Virginia. “Brittany,” he said, flashing up a photograph. “She’s 16 years old. She’s got six years to live because of the food she’s eaten.She’s eating her liver to death.

“Pastor Steve. He’s at the sharp knife-edge of this problem. He has to bury the people..By the way, this is what they get buried in.” He showed a picture of a coffin the size of a double bed.

Revolutionary road

The centrepiece of Oliver’s vision is the annual Food Revolution Day, which falls on 16 May. The event is all about making some noise and this year - in an attempt to break the world record for the biggest live cooking lesson - the loudest noise will come from hundreds of thousands of students around the world grating carrots for rainbow wraps. Oliver himself will be leading the action, streamed live through the TES Connect website.

What could possibly go wrong?

“A rainbow wrap is a really delicious slaw, with little bombs of feta cheese, wrapped in a flatbread. It’s perfect lunchbox fodder, really,” Oliver says. “It is about as good as I could think for a million kids cooking at once - and not losing limbs.”

When Oliver took part in BBC Radio 4‘s Desert Island Discs in 2001 at the age of 26, he said he thought the British public would put up with him for another three years or so, after which he would abandon the television shows and open a pub in Essex. He had just one more thing to do: he was opening his first restaurant, Fifteen, and wanted to staff it with disengaged young people whom he had trained up for the job.

The TV programme about the setting up of Fifteen, Jamie’s Kitchen, was the public’s first glimpse of the social activist lurking within the chef. And it impressed.

Food critic Jay Rayner, writing in The Observer, said: “If ever a product needed rebranding, Jamie Oliver is it; he was so overexposed.Jamie’s Kitchen, which opens with him screwing up the making of cheese on toast, is a self-conscious attempt to redress the balance. For all that, at its heart lies a noble plan: the creation of a restaurant that will give careers to 15 unemployed Londoners. It’s engaging television and Oliver himself is not an unpleasant presence.Surely he deserves the benefit of the doubt.”

Oliver’s blokey manner still irks some, but since he took up the cause of school dinners, he has also been described as a “national treasure” (The Times) and even a “saint” (The Guardian). And it was he who made school dinners into a national and now global issue that any politician worth their salt takes seriously (see panel, page 28).

Oliver started learning how to cook at The Cricketers pub in Clavering, Essex, which his father, Trevor, and mother, Sally, still run. Here, rather than at school, was where the young Jamie shone: he is dyslexic and found reading and writing difficult. He left Newport Free Grammar School at 16 with just two GCSEs, in art and geology.

However, by then Oliver knew he wanted to become a chef. He studied catering at Westminster College in London, spent three months in France and then got a job at Antonio Carluccio’s Neal Street Restaurant. In 1997, while working at the River Cafe, he was spotted in a documentary about the restaurant and offered his own show, The Naked Chef.

He has rarely strayed far from cooking since. One notable exception was the 2011 TV series Jamie’s Dream School, in which he enlisted high-profile experts such as David Starkey and Alastair Campbell to teach a group of disaffected young people, showing just how difficult teaching really is.

This was a one-off, but Oliver says he is “probably more passionate about education than anything else, actually”. As if to prove his point, the Jamie Oliver Food Foundation is an education charity. It was set up in 2001 to run the Fifteen apprenticeship programme, and now also oversees the Ministry of Food project - a network of food centres and cookery teachers set up in 2008 - and Food Revolution Day in the UK. The foundation is working with TES Connect to organise the record-breaking cooking lesson.

But although thousands of American students are likely to take part in the lesson, Oliver’s early attempts to bring the US round to his way of thinking didn’t start well. In 2011, three weeks into filming the second series of Jamie Oliver’s Food Revolution, Los Angeles’ board of education banned him from its public schools. Yet he carried on regardless and, with the backing of local organisations, ended up persuading the state to impose healthier food standards in schools. This year, he returned to hassle the politicians about providing clean drinking water for their schoolchildren.

“There’s nothing more heartbreaking,” he says. “When you work in very poor communities, they get free school meals but they can’t get drink out of a fountain. It’s just ridiculous. That’s in an area where you can see the Hollywood sign.

“When people talk about food deserts there’s probably no more [dramatic] juxtaposition [than Los Angeles], where you’ve got the fittest people in the world, some of the best chefs in the world, some of the most incredible farmers’ markets with biodynamics, organics and everything firing at 110 per cent, and all within sight of food deserts where you can’t get any fresh food within half an hour.”

In pursuit of happiness

Oliver is fully aware that his work is far from complete. In East London, filming for Food Revolution Day is taking place in the chef’s studio kitchen. This takes up only a small space of the large warehouse floor. Nearby is a large leather sofa and a coffee table with a stuffed fruit bowl and a tray of pastries sitting on it.

It does all come back to the food. The Jamie Oliver story isn’t one of a lad from catering college who got lucky. He knows what he is talking about. He has put in the hard graft, getting up at 4am to make bread and working late into the night. And his business acumen has made him very rich, reportedly worth around pound;150 million.

Does Oliver the businessman, the social activist, still feel like a cook? Does he still want to open that pub in Essex he told us about back in 2001, before Fifteen, before School Dinners, before Food Revolution? He laughs heartily and fiddles with his wedding ring.

“You know, selling the books and doing the TV shows is great. But I do like to think we’re just getting to a stage now where I’m kind of thinking differently. Even in the last two months, I just feel much more committed and more single-minded.

“I think positive social change is not that far away and I think it’s not that hard, but what needs to be done is for about 50 or 60 separate decisions and initiatives to happen at once, all followed by a five-year strategy.”

Could it be that Oliver has read the mood correctly once again? Certainly, he has access to the people who matter. As our chat comes to a close, he reaches behind his chair for a framed certificate: an honorary fellowship from the Royal College of General Practitioners, their highest award, which he was given a few months ago. “I got this the other day,” he says. “That is a big deal. I got a cape and everything.”

A cape. An appropriate gift for someone who really believes he is going to save the world.

To take part in Jamie Oliver’s live cooking lesson, visit www.tesconnect.comjamieoliver

Be a record-breaker with TES Connect

Jamie Oliver and TES Connect are together attempting to break the world record for the biggest ever live cooking lesson.

We are inviting teachers and their classes to take part in a lesson that will be streamed live through the TES Connect website on Friday 16 May at 2pm, and will be available as a pre-record on TES Australia.

Oliver will be teaching everyone involved in the class how to prepare a healthy and delicious rainbow wrap.

Register to take part and you could win chef’s hats and aprons for your class or even the chance to take a small group of students to the live event at City Hall in London.

The cooking lesson is the centrepiece of Oliver’s worldwide Food Revolution Day, a “global day of action for people to make a stand for good food and essential cooking skills”.

To register to take part or for more information, including an ingredients list, a lesson plan and a recipe, visit www.tesconnect.comjamieoliver

Ingredients of a life

James Trevor Oliver

Born 27 May 1975

1980-91 Attends Clavering Primary School and Newport Free Grammar School in Essex

1991 Studies catering at Westminster College in London

1994 Works at Antonio Carluccio’s Neal Street Restaurant, then at the River Cafe

1997 During a shift at the River Cafe, he appears in a documentary that leads to his first television series, The Naked Chef

2000 Marries Juliette Norton, better known as Jools. Becomes the face of Sainsbury’s supermarket

2002 Sets up his restaurant Fifteen, which trains young adults in the restaurant business

2003 Appointed MBE

2005 Launches the Feed Me Better campaign to accompany the TV programme Jamie’s School Dinners

2008 Launches the Ministry of Food TV show and campaign. There are now six Ministry of Food Centres in the UK, plus three centres and two mobile cookery classrooms in Australia

2008 Launches his Jamie’s Italian restaurant chain

2010 Receives the TED Prize

2010-11 Jamie Oliver’s Food Revolution TV show is filmed in the US in Huntington, West Virginia, and Los Angeles

2012 First ever Food Revolution Day takes place, with more than 1,000 events globally

Where it all started

Oliver’s breakthrough was his 2005 Bafta-winning television show Jamie’s School Dinners. This followed his battle to eject the now notorious Turkey Twizzlers from Kidbrooke School (since renamed Corelli College) in south-east London and introduce Hot amp; Kickin’ Chicken in their place. The issue took off. Not much later, the UK government announced new standards for food in schools and earmarked pound;500 million to improve food quality and kitchens.

But the campaign was not entirely without controversy. Take-up of school meals fell in the first two years after the government’s restrictions on junk food and there were fears that the packed lunches being prepared at home were even less healthy. But since 2008, the numbers eating school dinners have been rising again. In 2011, the last year a national survey was carried out, more children were signed up for school meals than in 2004.

And this year, universal free school meals for under-7s will be introduced, as well as a new curriculum that includes more practical cooking. That is some achievement for a lad with few qualifications who struggled at school.