Ultra-processed food linked to obesity

Food dubbed 'ultra-processed' has links to diseases such as obesity, dementia and cancer.
28 April 2023

Interview with 

Chris van Tulleken, UCL


A tray with a burger, chips, and soft drink.


If your lunch consists of a supermarket meal deal washed down with a bottle of fizzy drink then the chances are that you are consuming a fair amount of ultra-processed food or UPF. also known as ‘industrially produced edible substances’. It’s food made at scale and on the cheap. But what saves our wallets can cost us our health, with a growing body of evidence linking ultraprocessed food with heart disease, depression, dementia and cancer. Doctor and broadcaster Chris van Tulleken has been studying them as part of his new book, “Ultra-Processed People: Why Do We All Eat Stuff That Isn't Food ... And Why Can't We Stop?”...

Chris van Tulleken - There's a really long formal scientific definition, and it runs through a couple of pages because the guys who came up with the definition, well, the team that came up with it in 2010, were trying to encompass a whole range of different foods. But the shorthand is if it's wrapped in plastic and it contains additives that you don't typically find in a domestic kitchen like emulsifiers or stabilisers or sweeteners, then it's an ultra-processed food. And the additives aren't really the problem. They're a sign that a product is ultra-processed. Ultra-processing is much more than just additives.

Chris Smith - When did this become a thing?

Chris van Tulleken - I love that question because it was a thing in the 1980s when I was growing up, probably. I think you and I must be about the same age, I'm 44, and my mum would talk about the hazards of processed food. And for a long time people have worried about food processing. And when we process things, we alter them. Humans have been processing food for well over a million years. And processing we think is broadly fine. Ultra-processing came about because some scientists in Brazil were watching this incredible transition in the national nutrition status, where obesity went from being extremely rare, almost unheard of to being the dominant public health problem within a generation in 10, 20 years. But at the same time, people were buying less oil and buying less sugar. They were eating that oil and sugar in the form of biscuits and bread and these products that they decided to call ultra-processed. So what they were doing as scientists, and you'll get this very well and so will the listeners, is they were operationalising an idea, a concept as a hypothesis to be studied and in the next decade, in the last decade, the last 13 years since they created the definition, we've got a huge body of very robust data linking these products to, to really negative health outcomes.

Chris Smith - But why did we start consuming this stuff in the first place, Chris?

Chris van Tulleken - Well, it came about really in the 1970s when it gathered pace. So the problem with real food is it's always been expensive. So in my book I talk about the first example of an ultra-processed product was probably replacing butter with margarine. So butter's always been expensive. You've got to feed a cow grass, milk the cow, shake up the milk, make the butter, the butter goes rancid, and the whole thing's a pain in the neck. It's very expensive. And so even in the late 19th centuries in France replacing butter with something cheap, plant oil became a big project. And once the industrial chemists figured out how to turn a liquid plant oil into a solid fat and emulsify it with water, fake butter - margarine - was born. So margarine was probably the first thing to enter. It's simple cost saving. And part of the definition of UPF is that these products were about profit. And that's going to sound a bit abstract to some of your more scientific listeners, but it's actually really important when you consider food was invented by mainly female domestic scientists over the last few hundred thousand years. And they did it because they wanted to nourish their friends, their family, their community. This food is developed by very financialised companies. And I mean a very particular thing by that, these are companies that have very large owners. They're owned by asset managers. There's a very small number of companies that make UPF and they have absolute legal obligations to generate financial growth and profit. And that incentivises them very strongly to use the cheapest possible ingredients to make the most addictive possible food. And, I think addiction is an important part of this story.

Chris Smith - And what's the evidence that apart from being potentially addictive, that this is actually harming health?

Chris van Tulleken - We've got the usual three layers of evidence that you need to connect a potentially harmful variable with a negative health outcome. So we've got this sort of bottom layer of laboratory evidence and that gives us quite a lot of clues about how the food might be harming us. So we've got studies showing that ultra-processed food is soft and it's energy dense. It's energy dense because it's dry. It's dry because if you take the water out of food, if you dry it, it has a very long shelf life and it's energy dense because that's, that's palatable. And so we think this food is consumed at a rate that overtakes our satiety hormones. So when we eat real food, we have to chew it up. It's got a lot of water in it. As we consume the calories, we start releasing hormones that tell us that we're feeling full. Ultra-processed food is generally consumed much quicker than real food. If you think of supermarket bread versus sourdough bread. Anyone who makes their bread at home or buys expensive bread, and it is really expensive sourdough, will know that it's much chewier and denser than the kind of emulsified foams that make up more than 95% of the bread we all eat. So we consume it quickly and we've got lots of lab evidence about some of the additives like the emulsifiers and their effect on the microbiome, the colorings and some of the other additives and their effect on the brain. We've then got lots of epidemiological evidence. And the big problem for the epidemiologists, the population scientists who studied ultra-processed food, is their question was, is this just salty, fatty, sugary food? Like maybe we could have a simpler definition that just focused on the nutrients. And so they did statistical controls in all of the dozens of prospective studies that have been done looking at early death rates, dementia, inflammatory disease, metabolic disease, heart attacks, strokes. They controlled for fat, salt, sugar and fiber and lots of other things. And what they saw was that the effect on early death, dementia, all those negative health outcomes remained the same once you'd adjusted for the nutrients. So the processing does seem to be important. And then finally we've got a really good clinical trial. It's small, but it was conducted by one of the world's leading nutrition scientists, a guy called Kevin Hall at the National Institute of Health, in the States. And that chimes with all of the epidemiological data. So we've got pretty good evidence over the last decade that I would say there's real consensus among independent scientists. The people I work with at the World Health Organization at UNICEF, the scientists who aren't involved with the food industry, my colleagues at UCL, colleagues at Imperial, lots of colleagues in France, so big institutions around the world, there's real consensus building that this is the primary driver of pandemic obesity, this category of food.

Chris Smith - And what are we able to do about this? Because the whole world is effectively addicted to this sort of food production system. And it's going to take ages to unpick this.

Chris van Tulleken - My book proposes to the reader. There's a kind of eat along experiment that you can get involved with where you are being part of an experiment anyway, so eat along and as you learn about the food, it may become disgusting. Ultimately, I don't think it's really fair to ask individuals to change. This is the only available affordable food for most people. We need the government to label this food and we need to make real food much cheaper and we need to dramatically change everything about our food system. Most of all, we need to uncouple policy makers like the government and charities from the food industry. At the moment, the food industry has almost total capture of policy makers and all the basic research. So we need to disentangle that mess first.


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