A chilly late autumn day in 2013 and I am sitting in a central London branch of Pizza Hut trying not to be noticed. I wanted a table towards the back but they directed me instead to one here, in the window. I turn my body away from the glass, but it makes no difference. I am well over six foot, have a chest so big there are plans to build a high-speed rail link between my nipples, and have hair like an unlit bonfire. Plus I whore about on television. Sitting in a public place inconspicuously is not part of my skill set.

Quickly someone tweets that they have spotted me. Oh God. I fear my carefully honed reputation as a paragon of good taste is about to be destroyed. I feel like some Bible-bashing Republican senator who's been caught strapping himself to the wall bars in a secret torture garden, my appalling morals revealed. And so I am forced to explain. Pizza Hut UK has just launched a new product; an item so terrifying, so nightmarish, so clearly the product of a warped and twisted mind in matters edible, that I feel I have no choice but to try it.

I am doing this so others do not have to.

Most of the diners here today are going for the £6.99 all-you-can-eat buffet deal. Not me. I am ordering a large double pepperoni pizza with cheeseburger crust. I am consigning myself to my very own grease-stained, cheese-slicked gastronomic hell. I am doing this to shine a light on the way a deformed model of nutrition has come, in the past year, to play a key part in the debate around global food security.

Quickly it arrives. It's certainly not misnamed. The middle is standard Pizza Hut: a soft doughy base as sodden and limp as a baby's nappy after it's been worn for 10 hours. There is a scab of waxy cheese and flaps of pink salami the colour, worryingly, of a three-year-old girl's party dress. What matters is the crust. Each of the 10 slices has a loop of crisped dough and in the circular fold made by that loop there is a tiny puck of burger, four or so centimetres across and smeared with more cheese. It looks like a fairground carousel realised in food.

When I prise out one of the mini burgers, the greasy, insipid dough beneath looks like the white flesh of an open wound that's been hidden under a plaster. Do I need to tell you that the burger is a sweaty, grey orb of deathly protein? It is advertised as 100% British beef, but origin is irrelevant after this has been done to it. Those poor, poor animals. Surely they could have reached a more dignified end, perhaps by cutting out the trip to Pizza Hut altogether and going straight to landfill?

As I bite down on the meat, hot salty water leaks into my mouth. There is the fat-soaked dough, the wretched insult of the cheese sputum, and a general air of desperation and regret.

Pizza Hut UK admits that the cheeseburger crust pizza is 288 calories a slice, or 2,880 for the whole thing, well above an adult male's recommended daily calorie intake and above the previous Pizza Hut big dog. That was the BBQ meat feast stuffed crust, its doughy edges suppurating with cheap cheese, at 2,872 calories. Extrapolating from figures for that BBQ meat feast stuffed crust monstrosity, the cheeseburger crust has north of 120 grams of fat; the recommended daily limit for men is 95 grams. That could be mitigated only if the person who desperately wanted the cheeseburger crust pizza could find a friend with whom to share it. Or quite a few friends. That might prove a challenge.

What's most peculiar about all this is that in March 2011, Pizza Hut, along with many other big players in food retail, signed up to the British government's Responsibility Deal, an attempt to co-ordinate efforts by the food and drink industry to encourage healthier lifestyle choices by the public. One of the core pledges to which Pizza Hut signed up was: "We will encourage and enable people to adopt a healthier diet." And yet here they are, two years later, introducing to their menu an item that looks like it could clog an artery at 20 paces.

The head of the food industry division of the Responsibility Deal is the nutrition expert, Dr Susan Jebb. She declined to comment on Pizza Hut's gastronomic delights, having not had them inflicted upon her. However, between deep, weary sighs, she did say that "if we are going to support people in making changes to their diets then the food choices they are offered are a crucial and critical element". Indeed.

It's easy to dismiss the wretched cheeseburger crust pizza as a mere food curio, a tragic example of the terrible things done to perfectly innocent ingredients by those operating at the bottom end of the market. And it's certainly that. But it's also something much bigger: a rallying point for those talking seriously about the challenges of food security in the 21st century.

For years the debate has been solely around improvements to agriculture; about ways to increase yield and productivity while reducing impact on the environment. It has been about what sustainability actually means, and the need to revolutionise the way we make food or, as it's known, the supply side. Nothing has changed. That agenda remains firmly in place. The impact of climate change on our ability to feed ourselves really is going to be huge, and we need to be serious about taking measures to mitigate that.

Waste food adds 3.3bn tonnes of greenhouse gases to the planet's atmosphere and uses 1.4bn hectares of land – 28% of the globe's agriculture area

In the past year, however, a second debate has come to the fore, and this one is all about the demand side. It's not just about how we produce the food we eat; it's about how much of that food we're consuming – or not actually consuming, as the case may be. In the past year, for example, the volume of the debate around food waste has been turned up and up. In September 2013 the United Nations Food and Agriculture Organization released a report, Food Wastage Footprint: Impacts on Natural Resources [PDF], which revealed that the 1.3bn tonnes of food wasted globally each year caused $750bn worth of damage to the environment. The water wasted is equivalent to the entirety of the flow of Russia's Volga river. The waste food adds 3.3bn tonnes of greenhouse gases to the planet's atmosphere and uses 1.4bn hectares of land, or a full 28% of the globe's agriculture area. All to grow food that will never be eaten.

In November 2013 a report by the British government's waste advisory body, the Waste Resources Action Programme stated that Britons were still throwing away the equivalent of 24 meals a month, or 4.2m tonnes of food a year. Every day UK homes were chucking away 24m slices of bread, 5.8m potatoes and 1.1m eggs.

But there is another kind of waste, summed up by the Pizza Hut cheeseburger crust pizza, and that's overconsumption.

Eat food you really don't need to eat and that too has been wasted. Joining the middle classes, as millions across China, India, Brazil and Indonesia have done, provides access to loads of cool things like education, flat-screen TVs and karaoke machines. It also provides access to eating opportunities which might not be for the best. Like cheeseburger crust pizzas.

A full 18 months before it was launched in the UK, the cheeseburger crust pizza made an appearance in the Middle East. It's no surprise Pizza Hut chose to trial it there. Of the top 10 countries in the world for prevalence of type 2 diabetes, six – the likes of Kuwait, Lebanon, Qatar and Saudi Arabia – are in the Middle East, where it affects a whopping 11% of the population (compared with around 5% of the population in the UK). How better to decide where to launch the worst kind of junk food than by identifying the part of the world with the highest prevalence of an obesity-related disease? All these people who are developing type 2 diabetes – the kind related to lifestyle rather than the non-lifestyle related type 1 – will surely be total suckers for a pizza freighted with cheeseburgers.

Clearly, Pizza Hut now needs to focus its efforts on the boom lands of China. In September 2013, just as the cheeseburger crust pizza was arriving in Britain, a new study into the disease in China was published by the China Noncommunicable Disease Surveillance Group, based on a survey of nearly 100,000 people. As a measure of economic advancement, of an exploding middle class shamelessly demanding to eat as their equivalents in the west do, you couldn't hope to find much better. In 1980 less than 1% of the Chinese population was diabetic. By 1994 the figure was 2.5%. By 2001 it was 5.5% and six years later 9.7%. The report revealed that 11.6% of the Chinese population is now diabetic, with a staggering 50% showing signs of being pre-diabetic. Even the USA, that stadium for all things lardy and obese, the outright winner of the biggest-arses-in the-world contest, can only manage a diabetes rate of 8.3%. China has well and truly won the global competitive over-eating contest. As treating each diabetic costs around £900 annually in the UK, the financial implications of the disease are huge. If just a third of the pre-diabetics in China went on to develop the full-blown disease, in just a few years China could be facing a bill of around £300bn a year.

But there is also the simple issue of resources. As I was told by Professor Tim Benton, the co-ordinator of government and academic work on food security in the UK, if we all ate like the Americans we would need four planet Earths. We are all moving towards eating like the Americans. We are suckers for cheeseburger crust pizzas. And the last time I looked we didn't have four planet Earths.

Obesity is a huge problem in China. In 1980 less than 1% of the Chinese population was diabetic. 11.6% of the Chinese population is now diabetic (more than in the USA), with 50% showing signs of being pre-diabetic. Photograph: AFP/Getty Images

How do we solve this problem? If we study the numbers it all looks very simple. Along with the cheeseburger crust pizza, and the Chinese diabetes statistics, September 2013 also saw the publication of a study that weighed the benefits of techno fixes to agriculture to reduce greenhouse gas emissions, against simply fixing the world's diet. The report, written by Pete Smith of the Institute of Biological and Environmental Sciences at the University of Aberdeen, along with many other academics worldwide, concluded that if every single techno fix was introduced – renewable power generation, lower carbon methods of tilling, waste recycling and so on – it would reduce CO2 emissions by between 1.5 and 4.3 gigatonnes (a gigatonne being a billion tonnes). However, if the world changed its diet and went completely vegan, emissions would drop by 7.8 gigatonnes (though that ignores the positive impact that well managed ruminants have on the landscape and their ability to eat waste from agriculture).

There are many people who advocate just that. They say that if we all went vegan everything would be fine. And I'm sure they feel a warm glow of self-righteousness as they deliver these claims. There is nothing more empowering than making airy proclamations about the way forward, when you have no power whatsoever to make it happen. It's worth repeating: certain social groups in Europe and the US may wish to make these changes, but who fancies telling the newly emerged middle classes in China that they can't now eat like us? It's also true, of course, that if we stopped living in the 21st century everything would be fine. If we hadn't had an industrial revolution everything would be fine. Best of all, if, as a species, we hadn't been so damn successful, and we didn't keep being born and living longer, everything would be completely fine. There'd be fewer of us and, as a result, enough resources to go round. The fact is that, as the Smith report acknowledges, the world is not going vegan any time soon. That said, an optimal diet, as defined by the Harvard Medical School, which reduces the intake of animal proteins in rich countries and raises it in poor countries, would lead to a reduction in emissions of 4.3 gigatonnes. If that could be combined with advances in agricultural sustainability and improvements in yield, we might be getting somewhere.

According to Tim Wheeler, professor of crop science at the University of Reading, who is both deputy director of the Centre for Food Security and deputy chief scientific adviser for the British government's Department for International Development, it's only very recently that the debate's opposite parties have finally started talking. "Longstanding concerns with supply of sufficient and nutritious food to a growing population have spurred new ways of thinking about the links between agriculture and nutrition," he says. "What have traditionally been two separate schools of thought on food production and on nutrition have started to come together to tackle global food security challenges."

As he says, the dialogue can't come too soon; the over-nutrition issue is not something that can simply be dismissed as a "first world" problem. "Even in countries where stunting among children persists due to under-nutrition," he says, "there are fairly high and growing levels of adult overweight rates in urban and rural areas, with child overweight rates also rising rapidly in Latin America."

There are, it seems, an increasing number of places around the world where Pizza Hut could make a serious splash with that £17.25 cheeseburger crust pizza.

In the early summer of 2013 I was approached by a senior press officer at Tesco plc. Would I like to have coffee with Philip Clarke, the chief executive? Apparently he wanted to hear more about my views "as a food expert, on our commitment and our ideas on how to achieve it". How very flattering.

And how very, very odd. Historically, Britain's biggest retailer had also been Britain's most bolshy. Generally press inquiries about their business were met with a curt "no comment". They sold stuff, lots of stuff, and they didn't see why they should have to explain to filthy journalists how they sold that stuff.

Then a cheap, own-brand Tesco burger was found to be 29% horse, and everything changed. The discovery of horsemeat in four Tesco products, announced by the Food Safety Authority of Ireland on 14 January 2013, cast a long shadow over the year which has not yet receded. Their ups and downs have, in many ways, mirrored the debate around global food security and the role of large corporations in it.

Other food retailers in Britain including Iceland, Aldi and Lidl were implicated in the horsemeat scandal, but Tesco was the biggest player by far. The scandal was described as a wake-up call for mass retail. The question is will they all doze off again, given half a chance?

Within a few weeks of the discovery Tesco was taking out full-page adverts in newspapers to declare that they understood they had screwed up. They insisted that they had "changed". Shortly after that, the initiatives began. In early May they announced they were going to help their customers to waste less food. Which was nice. A week later, they announced they were going to help their customers to eat more healthily. Each time they made these announcements in radio or television studios they came up against a big man with a goatee beard, sideburns and a book to sell: me.

More than 3 million children die globally each year as a result of malnutrition Photograph: Ismail Taxta/Reuters

On waste food I asked why they didn't just stop doing the buy-one-get-one-free deals, the famed "bogofs" that encourage shoppers to buy more than they need?

Why didn't they stop selling bagged fruit and veg, with their unnecessary use-by dates, which infantilise customers and make them throw away food that is perfectly edible?

Tesco insisted that most of the waste was either in the field or in the home and not in store. This seems more than a little disingenuous. A lot of waste in agriculture is a direct result of supermarkets cancelling orders, or refusing produce on spurious quality grounds. Sure, it never reaches the supermarket shelves to be wasted there, but that doesn't mean the supermarkets aren't responsible for it.

Their initiatives on healthy eating were even less robust.

They admitted that the plan, which involved looking at their customers' eating habits via Clubcard information, required those customers to opt in to the programme. Anybody who opts in for healthy eating advice is probably not the person most in need of it. Demolishing Tesco's publicity-seeking initiatives, their attempts to recast themselves as the good guys post the horsemeat scandal, really didn't take much effort.

Hence the email requesting I sit down with the chief executive to explain what I thought they should be doing. I declined, and not very politely, because I really do have appalling manners. I told them I wasn't really up for acting as a free consultant to a multi-billion-pound company. Far better, I suggested, that I stick with being a journalist and they stick with being a supermarket.

I suggested we do a face-to-face interview with the boss of the company, all on the record. To my surprise, they agreed.

Philip Clarke's predecessor as chief executive, Terry Leahy, had been businessman as rock star, the buccaneer who wielded a well-cut suit like it was a lethal weapon. Clarke presents as the comfortably upholstered grocer. And it was the sweet-natured, local grocer who was there to meet me in his sleek boardroom in the heart of London's St James's. Tesco, Clarke said, was not just a retailer. It was a custodian of the food chain. "When you have 30% of the retail trade it comes with responsibilities. And I bitterly regret that four of our products were laced with horsemeat." He accepted that the deals they had done with producers had been too tough, that they needed to be in partnership with them. He acknowledged that the global marketplace had changed, that they couldn't just assume they could buy in food from all over the world because the emerging middle classes of China, India and Brazil may have got to them first. In what was a remarkable admission for the man who runs one of the UK's biggest food retailers, which competes furiously on price, he acknowledged that food was simply sold too cheaply for farmers to get the sort of return they needed to invest in the agricultural base.

"Because of growing global demand, it is going to change," he said. "There's going to be more demand and more pressure. Over the long term I think food prices and people's proportion of income may well be going up but we'll be doing our bit. Unless more food is produced prices must go up. It's the basic law of supply and demand." Philip Clarke had said the unsayable.

In the days that followed, Clarke's admission on the need for food prices to rise would make headlines.

He finished by admitting to me that Tesco had a big part to play in cutting down on waste, by not reneging on contracts and forcing farmers to dump crops. "There will have to be an end to that," Clarke said. Tesco would have to become better at forecasting their needs. And where they had ordered too much they would have to take responsibility "for selling them on the open market for a lower price than we contracted to pay". Unsurprisingly a lot of this openness and commitment to change was met with scepticism by both industry and consumers. After all, this was big, bad Tesco we were talking about. Surely they didn't actually mean it?

In October 2013, Tesco's report on waste within its own food supply chain showed that in six months it had wasted almost 30,000 tonnes: 21% was fruit and veg; 41% was bakery items

But still the initiatives came. In October 2013 they issued a report on waste within their own food supply chain. In the first six months of the year they had wasted almost 30,000 tonnes of what could have been lunch; 21% was fruit and vegetables, but a vast 41% was bakery items. They were filling their shelves with bread that nobody ever bought, let alone ate. Tesco estimated that across the UK food industry as a whole, 68% of all bagged salads were never eaten.

And so they started making commitments: where possible, food that had not been bought would be distributed to charities like FareShare, for redistribution to community projects and food banks. Bogofs on large bags of salad would come to an end, in-store bakeries would put less bread on display and they would remove display-until dates on bags of fruit and vegetables, which consumers said they found confusing. It's not the same as removing bagging altogether, but it is a start.

How seriously should all this be taken? Can a company like Tesco really be part of the solution? The honest answer is that we can't afford for them not to be. Mass retailers are a part of the landscape whether we like it or not. A privileged few may have lifestyles that enable them to avoid multiples altogether, but the majority will continue to shop there. We need Tesco to take seriously the challenges of food security. The real question is whether they can continue to do so in the face of pressure from shareholders. As 2013 came to an end, Tesco plc was faced with some truly horrible trading results. UK sales were down 1.5% in the third quarter. In Ireland they had plummeted 8.1%. The rest of Europe was down 4%. A year that had started with the company discovering there was some horse in its burgers ended with Tesco looking like a bit of an old nag.

It wasn't just the big food retailers who spent 2013 struggling with their responsibilities. In June, David Cameron, convened a "hunger summit" of world powers to thrash out a new international plan to combat malnutrition. He would have been forgiven for being a little disappointed by the turnout. He was the only actual leader to attend; the rest were mere ministers.

Around £2.7bn was pledged that day to tackle the problem, though it was pointed out by critics that in 2009, at another intergovernmental meeting in L'Aquila, Italy, nearly £15bn had been pledged, and very little of that money had ever been released. In any case, much of that turned out to be cash already pledged as part of other international aid initiatives.

During the hunger summit a 45,000-strong crowd gathered in Hyde Park, London, at a rally staged by the Enough Food for Everyone IF campaign, which argues that the issue isn't one of lack of food, but of lack of equal distribution and unfair taxation and aid regimes. It was proof, if proof were needed, that the issue had moved far beyond the tight world of policy wonks and academics. Food security was now officially part of the political agenda. That same week a report [PDF] in the medical journal the Lancet revealed that there had been a miscount. Previously it had been thought that somewhere north of 2 million children under five die globally each year of conditions they might otherwise survive if they weren't malnourished. The statisticians had redone their sums and discovered that the number was actually north of 3 million.

In November, a leaked draft of a new report from the United Nations Intergovernmental Panel on Climate Change, due for publication this spring, revealed that fluctuations in weather are already having an impact on global agricultural yields. It predicted that worldwide food production could drop by as much as 2%, while both population and demand continue to rise.

In short, the food security forecast during 2013 was gloomy and troubling, with possible outbreaks of calamity. But not everything was misery and disaster. Because in London that fine company Pizza Hut (UK) Ltd had decided that precisely the right moment had arrived for the launch of a £17.25 pizza boasting a crust containing 10 mini cheeseburgers, with an overall calorie count of 2,880. Many will tell you it's hardly the end of the world. It's just a pizza. And they would be right.

By itself, it isn't the end of the world. But it has the potential to make a bloody good contribution.

This is an edited extract of a new chapter from A Greedy Man in a Hungry World by Jay Rayner