A doctor has reveal the shockingly awful results of eating ultra-processed food for a month that included changes to his brain. Worst of all is the prevalence of processed food and the lackluster intervention of health authorities to regulate certain harmful foods.

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As part of an upcoming documentary for the BBC, Dr Chris Van Tulleken explores the effects of regular consumption of ultra-processed food (UPF). Eighty percent of the doctor’s calories for over the course of his month-long self-experiment came from UPFs, and the results will shock you – even if you’ve already read our article on four foods that will make you ugly, which includes processed food.

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The Risk of Processed Foods

Writing in the Daily Mail, Dr Van Tulleken says:

“A mere four weeks — that’s all it took for me to pile on enough fat to move from being a healthy weight to being overweight, putting my health at real risk. 

At the same time, my thinking became sluggish and I slept badly, lying in bed racked with anxiety, sweating with fears about everyday life. I developed heartburn as well as constipation. I got piles.

But worst of all, my brain rewired itself just as if I had developed an addiction to a drug of abuse. How did I wreak such terrible damage?”

The layman’s definition of an ultra-processed food is basically the following: the food must be prepared in a factory, wrapped in plastic and contain an ingredient you wouldn’t normally find in a home kitchen, such as emulsifiers, stabilisers, humectants (moisteners) or preservatives.

Although many UPFs make absolutely no claim to be healthy – chicken nuggets, microwaveable burgers, ready meals – others, such as sandwiches, bread products, cereals and low-calorie foods, do. Dr van Tulleken’s research shows just how much of a deception this really is.

Dr Chris Van Tulleken, before and after his month of eating UPFs image courtesy of dailymail.co.uk

UPFs have a long shelf life and are cheap to make; hence they are massively popular. In fact, UPFs make up almost two-thirds of the calories consumed in the UK, and one in five British adults eats a diet consisting of 80% UPFs.

There is particular concern about the consumption of UPFs by children and adolescents – hence the title of the documentary, ‘What Are We Feeding Our Kids?’ – since they are now estimated to consume two-thirds of their calories in the form of UPFs. One fifth of children now leave primary school (aged 11) with an obese body mass index.

Eating little but processed food

Consumption of processed food increased massively in the second half of the twentieth century, at the same time as obesity rates skyrocketed. The link between the two trends is well established, but still appears to be poorly understood by ordinary people.

A recent study (2019) by Hall et al., for instance, showed a clear association between weight gain and consumption of UPFs, and that the participants who consumed UPFs consumed more calories to satisfy their hunger.

Some of the results from the 2019 study by Hall et al.

Processed foods in a very real sense are as addictive as drugs. This is true in part because they bypass our body’s natural mechanisms for controlling hunger and satiety (fullness). Hall et al. showed, among other things, that we eat UPFs 30% faster than unprocessed foods. This is largely because they are very easy to chew and swallow; as a result, we eat them faster, before our bodies can reckon just how much we’ve eaten.

Manufacturers also aim for ‘hyper-palatability’, which might as well be code for ‘addictiveness’. They do this by looking to hit the so-called ‘bliss point’, where salt, fat, sweetness and crunchiness or chewiness combine to make a food that is extremely easy and, just as importantly, satisfying to eat. 

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The ease with which he could eat UPFs was one of the first things that struck Dr Tulleken when he began his experiment, which involved upping his intake fourfold. Although initially he found the experience pleasurable, noting how hard it was to resist eating UPFs once he’d started, the health problems quickly began to pile up.

As he recounts:



“I was starting to feel really unwell. I was constipated as UPF is typically low in fibre, and I developed piles. Then, in the third week, I was hit by sleep problems. The piles itched and kept me awake. The high salt intake was also waking me up, with me either needing to pee or feeling thirsty. Then I couldn’t get back to sleep.

Once awake, I’d wander towards the kitchen and rummage through the fridge for something to make me feel better. I got into a vicious spiral of sleeplessness and overeating and feeling awful.

I also started suffering horribly with heartburn and my libido felt non-existent. I felt old.

I felt heavier and, at the end of my diet, I wasn’t at all surprised by the changes in my body size and shape. The ‘before’ and ‘after’ photos (above) show I had fattened significantly, developing moobs and a bulging stomach. 

My weight had gone up by more than a stone (6.5 kg) and my body fat alone by 3 kg (6.6 lb).”

In addition, the change in diet affected his hormonal levels, as the hormones responsible for feelings of hunger and satiety increased and decreased, respectively. 

Processed food: chicken nuggets

Perhaps more worryingly of all, the diet altered the doctor’s brain, as revealed by MRI scans.

“And then came the really scary moment — an MRI scan of my brain after just a month on a high-UPF diet showed a significant increase in the connections between the reward centre and areas that drive repetitive automatic behaviour (see panel above right). Essentially, I’d become wired for cravings and mindless consumption of food; my brain was telling me to eat ultra-processed food without my even wanting it.

This is precisely the kind of thing you might see in a person with an addiction to alcohol, cigarettes or drugs. And it explained why I wanted more of these foods even in the middle of the night

Another scan showed I had a slight reduction in the grey matter of my brain — could this explain my muddled thinking?”

Image courtesy of Dailymail.co.uk

Dr Tulleken was so shocked by the results that he has now given up eating processed foods altogether. The weight has already begun to shift. 

“Mercifully, my piles got better within weeks, and my heartburn and anxiety stopped almost overnight. I knew I had to go cold turkey on UPFs because, as I learnt during the experiment, they are like an addictive substance: if your brain gets wired to addictiveness for it, you can’t moderate your intake, you’ll just crave more.” Six weeks after the experiment, an MRI scan confirmed that the changes to his brain were still in effect.

Although his claims about the addictiveness and intrinsic dangers of UPFs are rejected by an industry spokesperson during the documentary, Dr Tulleken is in no doubt that the government should take measures to ensure that people are aware of the risks and have the ability to choose their food appropriately.

“In Brazil, where obesity has risen by around 150 per cent in two decades, the government is warning people to avoid these foods completely, while France has pledged to reduce UPF consumption by 20 per cent in the next year — that’s how urgently it sees the issue…

“I would like to see healthy, whole foods marketed and promoted and subsidised, but I’d also like to see more direct action on UPFs…

“I don’t want to ban UPFs but I would like proper information on food labels based on the best independent science (i.e. not industry-funded) about the health risks.

“If we don’t acknowledge the role of UPFs in creating the obesity epidemic, we condemn our children to lifetimes of ill health.

“By the time they’re adults, it will be too late, their fragile growing brains wired to crave and eat ultra-processed foods — without them necessarily even wanting to do so.”

What Are We Feeding Our Kids? will air on BBC One at 9pm on Thursday, May 27
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