Here’s What Processed Foods Do to Your Brain

In Ultra Processed People, infectious diseases specialist Chris van Tullekenis takes readers on an engaging, revelatory and, frankly, disturbing tour of the science, history, economics and production of ultra-processed food. In this excerpt, he explains how UPF hacks our brains.

Over the past 150 years, food has become…not food, says Chris van Tullekenis. And this has massive implications. “A vast body of data has emerged in support of the hypothesis that UPF damages the human body,” he writes, “and increases rates of cancer metabolic disease and mental illness. That it damages human societies by displacing food cultures and driving inequality, poverty and early death, and that it damages the planet. The food system necessary for its production, and of which it is the necessary product, is the leading cause of declining biodiversity and the second largest contributor to global emissions.” Oof.

UPF has a complex scientific definition, first drawn up by a Brazilian team of researchers in 2010, but, says van Tullekenis, it can be boiled down to this: if it’s wrapped in plastic and has at least one ingredient that you wouldn’t usually find in a standard home kitchen, it’s UPF. “Much of it will be familiar to you as ‘junk food,’” he says, “but there’s plenty of organic, free-range, ‘ethical’ UPF too, which might be sold as healthy, nutritious, environmentally friendly or useful for weight loss (it’s another rule of thumb that almost every food that comes with a health claim on the packet is a UPF).” UPF now makes up as much as 60 percent of the average diet in the UK and the USA. “Many children, including my own, get most of their calories from these substances,” he says. “UPF is our food culture, the stuff from which we construct our bodies. If you are reading this in Australia, Canada, the UK or the USA, this is your national diet.”

(Related: 10 Things That Happen When You Stop Eating Processed Foods)

In the course of researching the impact of UPF, he decided to participate in a study with colleagues at University College London Hospital in the UK. The idea was simple: he would quit UPF for a month, then be weighed and measured in every possible way. Then, the next month he would eat a diet where 80 per cent of his calories came from UPF.

“I didn’t deliberately overeat during that second month,” he goes on to say (as if to emphasize that this wasn’t a Super Size Me gimmick). “I just ate as I normally do, which is whenever I feel like it and whatever food is available.” As he ate, he spoke to the world’s leading experts on food, nutrition, eating and ultra-processing from academia, agriculture and, most importantly, the food industry itself.

“This diet of UPF should have been enjoyable,” he says, “as I was eating food that I typically deny myself. But something odd happened. The more I spoke to experts, the more disgusted by the food I became.”

One of the goals of van Tullekenis’s book is to help us understand how everything from the marketing campaign to the strange lack of satisfaction we feel after eating is driving ill health. And that many of the problems we attribute to getting older or having children or work stress is caused by the food we eat. And if we’re able to give up UPF (there’s a whole chapter on that), the evidence suggests that this will be good for our bodies, our brains and the planet.

(Related: 7 Habits Of People Who Gave Up Processed Foods)


At the end of week two of my diet, I was still enjoying products like the Morrisons All Day Breakfast. A classic frozen meal, it comes in a three-compartment plastic tray with a film lid—768 calories of baked beans, hash browns, pork sausages, omelette and bacon, oven-ready in 20 minutes. It reminded me of the unbearable excitement of long-haul flights to visit my cousins in Canada when I was a child. My brothers and I could often persuade the crew to give us extra meals and we’d lick the trays clean. Air Canada’s 1986 macaroni cheese would be my last meal if I could arrange it.

The first complete frozen meals were, in fact, airline food: Maxson Food Systems’ ‘Strato-Plates’, so called because they were developed to be reheated on the new airliners of the day—Boeing’s Stratocruiser, introduced in 1947.

A few frozen meals were developed during the late 1940s, but it was Swanson’s ‘TV Dinners’ that took off in 1954. By then, more than half of American households had televisions, and this was the perfect hook. The dinners cost 98 cents and were ready in 25 minutes. Over the next three decades they would become ubiquitous. A 1981 picture shows Ronald and Nancy Reagan in the White House wearing matching red jumpers over matching white shirts, sitting in matching red armchairs on a matching red carpet, and eating TV dinners.

In the UK, we lagged behind on both purchases of household appliances – it wasn’t until the 1960s that TVs and freezers became common in UK households—and consumption of ready meals. But now we eat more of these ready meals than any other country in Europe. According to The Grocer, the UK’s ready meals category was worth approximately £3.9 billion in 2019. Almost 90 percent of us eat ready meals regularly.

While my All Day Breakfast sat in the oven, Dinah and I made some salmon, rice and broccoli for her and the kids. Twenty minutes of continuous preparation, using nearly unconscious skills handed down from our parents, as well as knives, three pans and a chopping board, resulting in dinner, yes, but also a big pile of washing-up and fishy hands. As we ate, Dinah read my meal’s ingredients out loud: ‘dextrose, stabiliser (diphosphates), beef collagen casing, capsicum extract, sodium ascorbate, sodium nitrite, stabilisers (xanthan gum and diphosphates), flavourings. Why are you eating diphosphates?’

The diphosphate stabilisers hold everything together through the freezing process so the water doesn’t end up in crystals on the surface. They’re just one aspect of what makes the All Day Breakfast such an enjoyable product, with the hash browns a little crispy and just the right level of salt and pepper.

Above all, it’s easy. While Dinah was still chewing her second mouthful, I was licking the container like I used to on those trans-Atlantic flights.*

Things started to change during the third week of my diet. I was working with Sam and Rachel designing a UK study to test whether it was possible to follow UK nutritional guidance while still eating lots of UPF and whether this would have any measurable effects. There is a vast amount of planning before a study like this: finding the money to do it and working out the details of study design. I was speaking with dozens of experts around the globe, asking them about the effects of UPF and the things that we should measure in our volunteers.

I’ve never learned about a potentially harmful substance while deliberately exposing myself to it, and before my diet I’d never even read an ingredients list. UPF is perhaps the type of food we inspect the least as it passes our lips.

I would come off a phone call to an expert in France or Brazil and then sit down to a banquet of UPF. I’d often eat during the call. It was like reading about lung cancer while smoking a cigarette, the basis for that remarkably well-evidenced self-help book I mentioned in the Introduction, The Easy Way to Stop Smoking, (which is even included in the World Health Organization’s ‘quitting toolkit’). Like many of the smokers who’ve used Allen Carr’s method, my relationship with UPF began to change.

By that third week, I was struggling to eat the UPF without thinking of things the experts had told me. Two comments in particular kept coming back to me.

The first was made by Nicole Avena. She’s an associate professor at Mount Sinai in New York and a visiting professor at Princeton. Her research focuses on food addiction and obesity. She told me how UPF, especially products with particular combinations of salt, fat, sugar and protein, can drive our ancient evolved systems for ‘wanting’: ‘Some ultra-processed foods may activate the brain reward system in a way that is similar to what happens when people use drugs like alcohol, or even nicotine or morphine.’

(Related: 50 Surprisingly Unhealthy Foods at the Grocery Store)

This neuroscience is persuasive, if still in its early stages. There is a growing body of brain-scan data showing that energy-dense, hyperpalatable food (ultra-processed but probably also something a really good chef might be able to make) can stimulate changes in many of the same brain circuits and structures affected by addictive drugs. We have this ‘reward system’ to ensure we get what we need from the world around us: mates, food, water, friends. It makes us want things, frequently things with which we have previously had pleasurable experiences. With many positive experiences of a particular food, in an environment in which reminders of that food are all around us, wanting, or craving, can be nearly constant. We even start to attach the wanting to the things that surround the food, like the package, the smell or the sight of the place where you can buy it.

But the part of the discussion with Avena that stuck with me most was a casual aside about the food itself. Paul Hart had explained how most UPF is reconstructed from whole food that has been reduced to its basic molecular constituents which are then modified and re-assembled into food-like shapes and textures and then heavily salted, sweetened, coloured and flavoured. Avena speculated that without additives these base industrial ingredients would probably not be recognisable as food by your tongue and brain: ‘It would be almost like eating dirt.’ I don’t know if she was being serious, but I started to notice that much of what I was eating had little more than a veneer of food. This was especially true of the snacks and cereals manufactured from pastes of raw materials, which had been fried or baked or puffed.

For example, I’d come to quite enjoy a Grenade Carb Killa Chocolate Chip Salted Caramel Bar as a mid-morning snack. It seemed a little healthier than a simple chocolate bar. I was doing the experiment because I was curious, after all, not because I wanted to deliberately harm myself in the name of science.

I inspected the ingredients after speaking with Avena. These bars, like many others, are constructed from very modified carbohydrates (the first ingredient is something called maltitol, a modified sugar, itself made from a modified starch, which is less calorific but almost as sweet as table sugar), protein isolates from milk and beef (calcium caseinate, whey protein isolate, hydrolysed beef gelatine) and industrially processed palm fat, all bound together with emulsifiers. On its own, as Avena says, it would likely be unpleasant. It’s made palatable with salt, sweetener (sucralose) and flavouring. As I ate these snack bars made from cow tendons, her words started to resonate in a way that stopped me enjoying the food quite as much as I had been.

The expert who made the deepest impression was Fernanda Rauber. Her work and ideas permeate this entire book. She told me at length about how the plastics from UPF packaging, especially when heated, significantly decrease fertility (and according to some experts, may even cause penile shrinkage). She also told me about how the preservatives and emulsifiers in UPF disrupt the microbiome, how the gut is further damaged by processing that removes the fibre from food, and how high levels of fat, salt and sugar each cause their own specific harms. And there was one small comment that stuck. Whenever I talked about the ‘food’ I was eating, she corrected me: ‘Most UPF is not food, Chris. It’s an industrially produced edible substance.’

These words began to haunt my every meal. They echoed and underlined Avena’s idea that without the colouring and flavouring it would most likely be inedible.

Ultra Processed People Cov

Excerpted from ULTRA-PROCESSED PEOPLE: Why We Can’t Stop Eating Food That Isn’t Food by Chris van Tulleken. Copyright © 2023 Chris van Tulleken. Published by Knolpf Canada, a division of Penguin Random House Canada Limited. Reproduced by arrangement with the Publisher. All rights reserved.

Next: What’s the Healthiest Cereal to Buy in Canada?

Originally Published in Best Health Canada