‘Soft and calorie dense’: Chris van Tulleken on how ultra-processed foods keep us hooked
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It's Christmas time, which means a lot of us will be indulging over the next few weeks. Mince pies, hot chocolate with squirty cream, bowls and bowls of crisps, tubs of toffee. It's what we used to call junk food, but in the past couple of years we've come to know it by another name: ultra-processed food.

And as scientists have studied ultra-processed foods in more detail, there's increasing evidence that they could be damaging our health in a myriad of ways. We know they're bad for us. And now we know just how bad ultra-processed foods can be for our health after two studies found they can cause harm similar to smoking.

But the term has also been somewhat controversial. Not everyone is convinced the UPF label is useful and there are still questions about exactly what it is about this kind of food that's the problem.

So today, we hear from this year's Royal Institution Christmas lecturer, Dr Chris Van Tulleken, about how food has made us who we are, how today's ultra-processed diets could be harming us, and why his top tip for Christmas is to cheat. From The Guardian, I'm Madeleine Finlay, and this is Science Weekly.

Nicola Davis, you're a science correspondent and it's becoming our yearly tradition that I get to speak to you about the Royal Institution's Christmas lectures that are going to be going out on our TVs over the next couple of weeks.

And this year, the lectures are given by Dr. Chris Van Tulleken. Tell me a bit about Chris. Chris is quite a well-known figure. So children might know him from the TV show Operation Ouch. And he's also been on other shows that parents might have seen, adults might have seen, including Trust Me, I'm a Doctor. He's also been on a lot of shows

He's an infectious disease doctor at University College London Hospital. So in first glance, you might think, well, what's that got to do with food? But he became interested in the importance of food after working on complex humanitarian emergencies where malnutrition played a crucial role in whether babies lived or died from diseases. He's since then become a leading voice campaigning against what we call ultra-processed foods.

So I started off our chat by asking what he was going to be talking about. Lecture one is the tube, the tube that goes from your mouth to your bottom and how you guard it with your eyes and your senses, how you prepare yourself for what's going to go in it.

and then what happens inside that tube. Lecture two is for me the most exciting because it's going to be a real exploration of the next layer. So once the food leaves the tube, what happens to it in your cells? How do you turn your food into your thoughts and your actions and all the things that make you you? And also how do you build your body from your food? Lecture three is a history of processing because humans are obligate processibles. We must process our food to survive.

And yet, as we all know, food processing has become controversial, has led to some health problems. And so it's an exploration of the history of processing and the different reasons it's done. And what do we mean when we talk about processing? I say in the olden days, I mean, in our evolutionary past, what did food processing look like? What was it that we were doing that set us apart from other species? The first thing we started to do was probably cut food.

You have to spend an immense amount of energy killing your food and then biting off chunks of it and chewing up those chunks. And if you can kill your food, skin it and chop it up, you suddenly have a lot more blood to send to other bits of the body, particularly your brain. And the first real evidence of cooking is blood.

probably about half a million years ago. It's cooking that releases humans from the trap where you have to have this very big, thick skull to support the jaw muscles and the jaw to chew up unprocessed, uncooked, raw food. So cooking is the thing that allows the brain development. You get more energy out of your food, your food becomes cleaner, and that's a sort of massive leap forward.

Nicola, the lectures sound really interesting, but as you mentioned, Chris is really well known now for his writing on ultra-processed foods. So how have we gone from...

from processing being something that has helped make us who we are as humans to it being this controversial and potentially harmful thing? Well, I think the important point is what do you mean by processing? You know, cutting up meat and cooking it, smoking fish or boiling potatoes. That's one thing. But by ultra-processed foods, experts mean something else. And these have...

lots of ingredients that make them super, super tasty. This is a phrase known as hyperpalatable. You know, you just can't really stop at one or two of those little biscuits. You have to eat the whole packet. And these foods often include ingredients that you don't usually find in home-cooked

chemicals that you might not even know what it is. They're often quite industrial, can be stored for a long time, and they're usually packaged in very sophisticated ways, which again is all about increasing the desire for them. And so we're talking here about things like fizzy drinks and breakfast cereals and even those faux meat burgers and certain types of non-dairy milks.

And there have been a number of studies suggesting a diet high in these ultra-processed foods, or UPFs as they're known, is pretty bad for you. And there was a study that came out earlier this year, the largest review of its kind, that found that UPFs were directly associated with 32 adverse health outcomes. And these included a higher risk of heart disease, cancer, type 2 diabetes, even early death.

And this all sounds very bad, but there is still quite a lot of discussion between experts on what we can take from these studies and...

There's even some disagreement on what this all means. Yes, I think it's important to be clear about what that disagreement is about. First of all, these studies, they show correlations, not causations. There's always the question of, is it that people who eat a diet that's rich in these foods, perhaps they have other characteristics that might be related to poorer health?

And diets are very, very hard to study. Often they rely on people filling in questionnaires about the kind of foods they eat or remembering what they've eaten in previous weeks or so on. But there's also a big question here. If these foods are so bad for you, how much of that is down to the fact they are also often high in salt, fat and sugar? And how much of this is actually down to how they're marketed? Is it the properties of the food itself? Is it about how

how much of a diet they're taking up. And this is something that Chris raised when I spoke to him. So we've got lots and lots of good experimental data going back 30 years.

that foods that are high in salt have effects on our blood pressure and our heart. Foods that are high in saturated fat do similar things. Sugar damages our teeth and puts it at risk of weight gain and metabolic disease. And the excessive consumption of calories leads to weight gain. So those are the kind of pillars of nutrition science. There are some other things we know. If food is soft and

and it has a lot of calories per gram, it's also likely to be eaten quickly. And we think that speed of eating soft food, energy dense food predisposes to weight gain and weight gain causes other health problems. So this is the heart of the argument in nutrition science at the moment is, is UPF just another way of describing fatty, salty, sugary food?

We have two randomized controlled trials now to show that even when you fix the salt, fat, sugar levels and fiber levels, in fact, and protein levels, in fact, there is something about the way the food is processed that leads people to eat more. It's the salt, the fat and the sugar that we're pretty sure is doing the harm of

but it's the ultra processing that is making you eat too much of them. And by ultra processing, marketing is part of ultra processing. It's part of the definition, but it's also the additives, the flavoring, the coloring, the textures, the softness, the packaging, the snap when you open the bottle and the marketing campaign and availability that surrounds the food. So the processing is all of that and it is what makes you eat too much of it and puts it in front of you.

Nicola, just reflecting on what Chris said there, the fact that this food is so carefully designed and not just what's inside it, but how it's put in front of us to make us eat more of it. You know, today, more than half the average diet in the UK and the US is ultra processed, which sounds like a lot, but I try and be healthy. You do enough Science Weekly episodes and you begin to really think about your gut microbiome and things like that.

But actually, when I look at my diet, I'm easily up to that 50%. I love oat milk in my coffee in the morning. I will happily eat bread from the supermarket on the way into work. I'll buy a yogurt pot from a well-known food chain. I mean, it's really easy to eat this stuff. I mean, a lot of this is sort of the modern food and the modern landscape in which we live, which I think is really important to remember. And it actually talks to another bone of contention, though, about sort of UPS and dieting.

how the term is used and how it's deployed in conversations with the public. For example, some scientists say not all ultra processed foods are equally bad for you. So if you compare, for example, whole grain supermarket bread with donuts, they're both UPF. But I mean, I think one would assume would be healthier than the other. It can be better to focus more on things like the salt, sugar and fat content because

Because a UPF term isn't really designed for making individual dietary choices. It's really there to be used to help improve our food system and our food landscape and for regulation the industry that doesn't always have our best interests at heart. The UPF definition is nine paragraphs long and it has lots and lots of important concepts in it. But it was never designed for consumers nor as a policy instrument.

Now, when it comes to actually how are we going to, for example, label a product, the ultra processed food definition doesn't work. The reason it doesn't work is twofold. First of all, at product level, it isn't precise enough that the food industry can't argue their way out of it. So one of the criteria in the definition is the use of additives not typically found in domestic kitchens or the use of additives that are cosmetic or industrials.

And of course, there are additives that sit in a weird space now. Xanthan gum is an additive that in a research study, you'd say, well, that is an industrial additive. So we'll call that food ultra processed. But you can buy xanthan gum and cook with it at home. And lots of patients with celiac disease do that. The second problem is it has a big loophole.

When the definition was created, it was created to label all these kind of quite extreme products that were all obviously pretty harmful. In the UK now, we have a lot of products that are very high in energy, salt, fat and sugar, but they aren't quite technically ultra-processed because they might not have any additives. And this is the case with supermarket ready meals, for example. A ready meal lasagna might not technically be ultra-processed,

but it has all the properties of ultra processed food that will harm you. And it's been developed using the same technologies and marketing tools. So you'll still eat too much of it. The really important thing to say about it is while there is definitely a spectrum, the supermarket whole grain bread has a much healthier nutrient profile than a chocolate bar.

What seems to be the case is that more than 99% of ultra processed food in the UK is misaligned with our dietary guidance. It's all high in calories, salt, fat and or sugar. And so let's move on to a slightly more positive side of this. What can we do? What should we be eating? How can we...

as individuals take action. As you say, this is a systemic problem and it's something where a lot of people perhaps don't feel very empowered. So what can we do? How can we take action to eat better? I think a lot of people can't do anything. They feel disempowered and they are disempowered.

This is the injustice in the food system. This is the food environment created by a relatively small number of transnational corporations. It creates food insecurity and lack of healthy food availability for millions of people. So I absolutely refuse to tell anyone what to eat or what to buy. My interest is really only in...

advising government or advocating for big structural changes. And in terms of that, we know very well what we need to do. The ultra processed evidence tells us very clearly that the product portfolios and the companies we need to regulate, as well as studying nutrition, I do a lot of work with economists,

And one of the things we can use the company's own financial data to do is to show that they have a very limited ability, even when they want to change, their investors really constrain them and stop them making, improving the product portfolios. This tells us we need government intervention. In fact, the cost of obesity to the NHS alone is around 100 billion per year. So essentially, that's a subsidy that we all pay because of the actions of the food industry.

So Nicola, the point is really that we have to regulate the industry and...

that none of us should berate ourselves for eating ultra-processed foods because we live in this food environment that actually makes it really, really difficult to avoid them. Yes, I think this is an important point. Most of us are at the mercy of the money in our purses, the time we have, and fundamentally what's available for us to purchase in the shops as well. And I think that it's one of those terms that

It's important to understand where it's helpful, where it can be used, and also what the limits of that term are. I'm very glad that you've made that point because, you know, it's Christmas, which means a lot of us, I personally, will be eating a lot of ultra-processed foods in the next month. And as I said, I'm not going to be alone in that. Well, yes, I mean, I did actually ask Chris how he manages the festive season. Yeah.

What I do is I buy quite a lot of pre-prepared, some of it will be ultra-processed Christmas food, you know, the tinfoil trays of potatoes and veg and the sprouts with the bacon. And I take it out of its containers the night before and put it in ceramic. And then I put it in the oven and tell my family that I cooked it. And it saves me a massive amount of time. Everyone loves it. I actually spend time with my family on Christmas Day. And my other...

I don't know if this is a tip, but I serve chicken, not turkey. And I get two chickens and I tell everyone it's micro turkey. And it's a new thing. And my family, I don't know if anyone would listen to this and find out, but they love it. Chicken is a very nice, juicy meat. It's much easier to buy at Christmas time. So that's my other thing. And it's easier to cook than turkey. This is your top tips. Yeah, I just, I don't want to,

guilt anyone. The food we eat is like the water we drink and the air we breathe. You know, it's like, do I have any tips for people struggling in London with air pollution? No, no, I don't. You know, I've got nothing to say. Just we need structural change. You can change how you vote, you can change what you campaign for, but you can't change the air you breathe off your own bat or the house you live in or the food you eat. A big thanks to both Nicola Davis and to Dr Chris Van Tulleken.

If you're curious to find out more about what happens in our bodies when we eat and how we can repair our relationship with food, the Royal Institution Christmas Lectures will be on BBC4 on the 29th, 30th and 31st of December at 9pm and on BBC iPlayer from the 29th of December. And for Nicola's reporting on the lectures as well as her look at why nutritionists overindulge at Christmas too, head to theguardian.com.

Now, I'd like to ask for your help. From bombshell elections to devastating conflicts, as well as transformative sporting and cultural moments, 2024 has been another extraordinary year. The Guardian has been there to cover it all, with rigour and a commitment to putting the facts first. If you appreciate honest, fair reporting and you want to power our journalism and podcasts,

through another crucial 12 months, please consider becoming a supporter today by following the link in the episode description. Thank you. And that's it for today. This episode was produced by me, Madeline Finlay. It was sound designed by Tony Onuchukwu and the executive producer is Ellie Burey. The Science Weekly team is on a break for the next two weeks, but we'll be running some of our favourite episodes from the year starting Tuesday.

So see you then. This is The Guardian.

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