Leon co-founder Henry Dimbleby says our diet is killing us and planet

The stark statistic isn't accidental; 57 per cent of our diet is now highly processed, which is linked to everything from cancer and depression to diabetes and heart disease.

Henry Dimbleby, the chef, cookery writer and co-founder of healthy fast food chain Leon, was tasked five years ago with leading a national food strategy. He investigated everything from land use, to health policies, and the powerful lobby, which has an interest in peddling salt, sugar and fat laden food that we end up craving.

Henry Dimbleby singles out foods high in salt sugar and fat as harming the nation's health

Processed foods, he concluded, are cheaper by the calorie than fresh produce, and our eating habits are informed by a complex global system that is destroying us and the planet. A perfect example is the Wye river, polluted by manure from intensive chicken farms: "You are deforesting parts of America to grow soya beans, to bring over here to feed chickens, which then pollute our rivers, and make us sick."

The 52-year-old, who lives near London Fields, published a Government paper arguing for a joined up food policy, including extending eligibility for Free School Meals, a salt and sugar tax, and curbs on advertising junk food to kids.

Citing the Government's failure to tackle obesity, he resigned as 'food tsar' in March and is now free to speak out. He has published Ravenous with journalist wife Jemima Lewis, suggesting how we might feed ourselves affordably without killing ourselves and the planet.

"We realised when we published the first part of the food strategy that no-one was going to download a Government document and it needed a better airing," he explains.

"We were trying to change the way that people understood the food system. Some ideas were factually incorrect and you can't create change unless people understand the problems."

Henry Dimbleby and Jemima Lewis Ravenous is published by Profile Books. (Image: Courtesy of Profile Books)

Dimbleby's book makes you question how much power we have over the systematic promotion of processed, unsustainably-produced food.

"I have three kids who have been through the various stages; one became vegan, one could only eat meat, and my 11-year-old daughter would eat chocolate all day long," he says. "When I think about personal responsibility versus being trapped in a system, it's like living in a swamp, the environment makes it very difficult for adults and children to eat well, you are bombarded with advertising, and in places like service stations it's almost impossible to buy food that isn't ultra processed. But if you live in a swamp, you do your best to teach people swampcraft."

When it comes to parenting he says "the reality is you have much less control over your child's health than you like to think, but there are certain things you can do.

"There are things that are not in our house, like breakfast cereal, which to me is symptomatic of everything that's wrong, the fact that breakfast is basically pudding."

Favouring Finnish-style nudges rather than dictats, he's working with ad gurus M&C Saatchi on "how to make people think about reducing meat in ways that don't become a culture war."

And he hopes that Ravenous reaches policy makers.

"Typically the narrative among people in power is it's all about education. But experience with free markets shows that unless Government intervenes to break the commercial incentive for companies to create food that ends up making us sick, we aren't going to get better.

"It's completely unreasonable to expect someone in a supermarket to have the amount of knowledge required to decide which foods to buy. It took me the best part of four years to understand it then summarise it. You talk to people and they just want the government to ensure their food is environmentally friendly."

Dimbleby says the 'nanny state' jibe against measures such as a sugar tax are "invented by lobbyists for the food companies," and believes the public don't see health legislation as repressive. 

"There are things that people don't want to be told, like eat less meat because for some reason that is connected to identity for a lot of people, but they are crying out for intervention on health and animal cruelty. I was chatting to a senior Labour figure involved in banning smoking, who said 'at the time eveyone told us it would be electoral suicide, but instead people said how nice not to have smoke everywhere'."

While he thinks the "penny has dropped on the environment," he is concerned that "the goverment has gone backwards" on health issues. But he believes we are reaching a tipping point where economic arguments will focus minds.

"The single biggest thing holding our economy back is 2.5 million out of work due to chronic illness, and how much is related or exacerbated by diet? That means the NHS needs more money, GDP stagnates and tax receipts are down, any Goverment will be crippled by that."

If taxing unhealthy foods is "particularly difficult in a cost of living crisis" he points to wider inequality issues, with nearly a quarter of children elibible for Free School Meals living in households earning £7,400 or less.

"That's not a problem with the food system that's a problem with how you manage the economy."

Dimbleby's parents are broadcaster David and cookery writer Josceline, an early adopter of reducing meat with 1994 cookbook 'Almost Vegetarian' and "a quiet revolutionary."

"She was always developing recipes for cook books, so quite often you would be eating salad in winter and Christmas pudding in summer. Because she prided herself on her recipes working, she was incredibly careful about writing things down and we were not allowed in the kitchen when she was cooking but we gained an experience of how to eat and enjoy a wide range of flavours. She was an incredible pioneer and sold two million cookbooks without doing TV. One of the pleasing things about giving talks is I get many more people saying 'are you Josceline Dimbleby's son? than are you David Dimbleby's'."

As for the future he thinks politicians' understanding of what the electorate wants is "flawed."

"I am more optimistic than I was six months ago, I sense that the penny has dropped that we can't afford to carry on doing this. There's a lot of human misery, suffering and illness grandchildren who won't know their grandparents. The government has a lot more space to act than it thinks it does."

Henry Dimbleby is in coversation with presenter of Radio 4's The Food Programme Sheila Dillon at the Proms at St Jude's Lit Fest on Sunday, June 25 at 1.30pm.