Dr Chris Van Tulleken doesn’t want to ban bacon sandwiches outright – but he does have a serving suggestion. “I just want there to be a warning on the packet saying this food is associated with increases in obesity, cancer and death,” says the 42-year-old television doctor. “And then you can go ahead and enjoy it.” 

After coming for our bacon sarnies he wouldn’t stop there: fish fingers, baked beans, all the childhood staples which most of us grew up on (and have returned to sneakily for lunch during this year of lockdown). “In Britain, we don’t have a food tradition,” Dr Van Tulleken says, witheringly, with the result that, “British cooking has all been ultra-processed.” 

Ultra-processed is the stuff of ready meals, biscuit tins, breakfast cereals and school lunch boxes. To deconstruct the bacon sandwich, “ultra-processed” would typically apply to the industrialised white loaf, mass produced and chemically cured meat – and even the brown sauce. 

“UPF”, as Dr Van Tulleken calls it, is a food group that can be identified by a long and largely incomprehensible list of chemicals, colourings, sweeteners and preservatives on the back of a packet, and is what most of us are eating every day. In Britain, an estimated 56 per cent of all our daily calories comes from ultra-processed foods, a figure that rises to 64 per cent among children.  

And, according to Dr Van Tulleken, who has presented numerous television series for the BBC alongside his NHS career as an infectious diseases doctor at the Hospital for Tropical Diseases, part of University College London Hospitals, it is fuelling an addiction that is slowly killing us.

In filming his new BBC programme What Are We Feeding Our Kids? which airs this week, Dr Van Tulleken, a father-of-two whose wife, Dinah, is a fashion journalist, put himself on an 80 per cent ultra-processed food diet for four weeks in a real-life experiment.

“It had a catastrophic impact on every aspect of my health and my life,” Dr Van Tulleken says. “My libido, piles, heartburn … everything got worse. I was anxious, depressed – and it was all self-perpetuating.” Sleeping was a struggle, too as was always feeling hungry. Dr Van Tulleken explains that UPF is designed to trick the body into overeating: “Things like monosodium glutamate (MSG) send a signal to your brain telling you this is nutritious. But when you digest it is there is nothing there – so you keep eating.”

The diet, he estimates, aged his body by 10 years, but more disturbing was the impact on his mind. MRI scans taken after the experiment confirmed that the junk food had rewired his brain; strengthening the appetite and reward neural pathways into patterns more familiar with a drug addict.

Several months on, and subsequent scans have shown the neurological changes have yet to be reversed. Particularly worrying, he adds, is the impact of this food on developing brains – particularly given the fact that according to his programme, currently two out of every three calories consumed by children and adolescents in Britain is derived from ultra-processed foods.

“Most children in this country begin their lives on ultra-processed food,” he says. “What is it doing to them? The astounding thing is we have no idea.”

Since the programme, he has gone cold turkey, expunging all ultra-processed food from his diet. It has also prompted a reappraisal of what he is feeding his own children. 

When his three-year-old, Lyra, was an infant, he says he fed her “organic sachets of multicoloured baby food” (he carefully avoids naming any brands in his programme). “There is this middle-class set of products we all buy and it is all ultra-processed,” he says. “Everything I was feeding Lyra was ultra-processed and I didn’t realise it.”

He has now eschewed such products with his 11-month-old, Sasha, and is instead just feeding her smaller portions of adult foods with less salt. “The whole notion of baby food is just weird,” he says. “It’s a confection of the food industry.”