The Damning Truth: What Ultra-Processed Foods Really Do to Your Body

In November 2025, a group of the world’s leading experts on ultra-processed foods (UPFs) came together to review the latest evidence for the overall impact of these foods on our health for leading medical journal The Lancet. The findings were damning, concluding that UPFs have adverse effects across nearly every single organ system in the body. For the UK, a country where the average person consumes 56 per cent of their daily calories through UPFs, it was particularly bad news. “Overall, poor diet has overtaken tobacco globally as the leading cause of early death,” says Chris van Tulleken, a professor at University College London and author of Ultra-Processed People. “In the UK, our national diet is ultra-processed food, and for several generations, our national dishes were created for the purpose of profit. If you think in terms of fish fingers, baked beans, the cereals we all eat for breakfast and the supermarket bread, these aren’t traditional foods that were made to nourish us, they are entirely industrially produced.” Around the world, the more that scientists have looked, the more they have discovered that an excessive intake of UPFs is linked to innumerable illnesses. “UPFs have been linked to a variety of chronic diseases,” says Andrew Chan, a gastroenterologist and professor at Harvard Medical School. “There has been an association with obesity, diabetes and other metabolic diseases which also seem to be risk factors for cancer. One plausible mechanism is that UPFs may contribute to metabolic changes that are potential predisposing factors for early-onset cancer.” Let’s take a look at some of the key organ systems which are particularly affected by over-consuming heavily processed foods. The organs most vulnerable to UPFs Liver In 2023, researchers at the University of Liverpool carried out a study of more than 60,000 people where they showed that the more UPFs a person consumes, the greater their risk of fatty liver disease. This is a serious and progressive condition where the gradual accumulation of fat drives liver scarring and impairs liver function. The paper highlighted one less well-known risk factor, namely the presence of industrial chemicals in the packaging of ready meals, snacks and other UPFs which disrupt the body’s hormones, and have been linked with accelerating the progression of fatty liver disease. The primary reason, however, is that UPFs lend themselves perfectly to the rapid acquisition of dangerous levels of liver fat. Our body has a very sophisticated way of regulating how many calories we consume, but UPFs are leading this finely honed network astray. “UPFs are soft, energy dense, flavoured, coloured, and have very precise ratios of salt, sugar and fat, all optimised so it’s very hard to stop eating,” says van Tulleken. “Open any crinkly packet of crunchy stuff, or eat any ready meal, and see how little it satisfies you and how easy it is to eat a huge number of calories quickly.” The consequences of this overconsumption are simple but devastating – we end up creating excess body fat. We can store a certain amount of this in skin cells, but after a while our body is forced to find extra space for all this fat, and one of the first places it chooses is the liver. “People who eat UPFs are more likely to eat more food over time,” says Dr Alex Henney, an academic clinical fellow in diabetes and endocrinology at the University of Liverpool. “This is because they’re more heavily filled with fats and refined carbohydrates compared to proteins and healthy fibres. This then leads to this excess storage of liver into the liver.” The gut The gut plays a crucial role in the body’s appetite regulation network, impacting how full or hungry we feel. However, its ability to control appetite is tied to the food matrix – the complex physical and chemical structure of a whole food. Because UPFs are typically created from pre-digested ingredients, the gut does not get the typical signals that it’s evolved to receive, leading us to overeat and acquire more liver fat. “Because the food matrix has been destroyed, this disrupts gut microbiome signalling,” says Dr Henney. “It’s exacerbated by the fact that many UPFs are heavily filled with fats and refined carbohydrates, compared to proteins and healthy fibres.” According to Mathilde Touvier, a professor at the French National Institute for Health and Medical Research and one of the authors of The Lancet report, there are growing concerns that excessive consumption of certain additives within a high UPF diet, like emulsifiers and sweeteners, is causing localised harm within the gut itself. “UPFs are associated with an increased risk of Crohn’s disease, which is an inflammatory bowel disease,” says Prof Touvier. Some animal studies have shown that gut inflammation can lead to the development of colon cancers, and a major new study called PROSPECT is now attempting to see whether UPFs could be behind the startling rise of bowel cancers in the under 50s. Some early data is already supporting this hypothesis. Last month, Prof Chan and his colleagues published a study which found that women under 50 who consume up to 10 portions of UPFs per day – for example through snacks, ready meals, packaged cereals or fizzy drinks – have a higher risk of developing bowel polyps than those who consume only a handful (3.3 servings) per day. Polyps are abnormal growths in the lining of the intestine which arise due to cell damage and can act as a precursor to cancer. “We know the vast majority of colorectal cancers arise through a polyp phase,” says Prof Chan. While researchers have yet to hone in on the exact components of UPFs which appear to be driving polyp formation, Prof Chan suggests “some of it may be related to specific bacteria [which feast on the components of UPFs], but it may also have to do with the kinds of metabolites those bacteria produce in the gut which disrupt the gut’s ability to repair itself. Some studies in animal models also suggest that some emulsifiers may have an effect on the health of the gut lining.” Heart Over time, consuming a high amount of UPFs can increase the risk of various cardiovascular diseases, from stroke to heart disease. One recent study in the US even managed to pinpoint how some UPFs appear to be worse for the heart and blood vessels than others, with the main culprits being sugary drinks and processed meats. Animal research has also shown that common UPF additives such as sulphites and the flavour enhancer monosodium glutamate (MSG) have been linked to cardiac tissue damage and the hardening of blood vessels. On the other hand, UPFs such as packaged bread, breakfast cereals, savoury snacks, and yogurt or dairy-based desserts were not as highly linked with risk of cardiovascular problems. “Not all UPFs increase cardiovascular disease,” says Josiemer Mattei, an Associate Professor of Nutrition at the Harvard T.H. Chan School of Public Health. “Some may be neutral or even protective because they have other important nutrients that counterbalance the negative effects.” Why? We know that UPFs disrupt the gut, and so the gut-brain axis (which allows chemicals produced in your gut to influence your cognition) may provide one clear explanation. People with more gut inflammation as a consequence of a poor diet, are more prone to depression, while people who consume more UPFs also tend to consume too little fibre. This is broken down into useful gut chemicals known as short-chain fatty acids, which can help to protect the brain. Alex DiFeliceantonio, an assistant professor at Virginia Tech’s Fralin Biomedical Research Institute says, “Increasing the fat and sugar content has been shown to change the brain’s response to a milkshake, so it’s possible that the typical nutrient profile of certain UPFs is leading to functional changes [in the brain].” What needs to be done? While all of us can make better choices to reduce UPFs in our diet, experts also feel that the Government needs to do far more when it comes to introducing stricter food policies. Van Tulleken is calling for the Government to introduce stronger regulations when it comes to the content of unhealthy foods and how they’re marketed. Like cigarettes, van Tulleken believes that the UK should introduce far stronger warning labels on foods which are high in salt, fat, sugar or calories. This is already being applied with success by various countries in South and Central America. “Once the food has a warning label, it then gets a tax. You can’t have a cartoon character on it, you can’t make health claims on that food, you can’t sell it to children, you can’t have it in schools or hospitals or prisons, and the military doesn’t procure that food,” says van Tulleken. “We need all of those things, along with proper, mandatory reporting of unhealthy food sales with lots and lots of granular detail, so we know exactly what is going on.” Easy UPF swaps Nichola Ludlam-Raine, specialist registered dietitian and author of the book How Not to Eat Ultra-Processed, shares her recommendations for how to replace common UPFs in your diet with healthier alternatives. 1. Sugary fizzy drinks Replace with: Kombucha or sparkling water with lemon Nichola says: “With any type of sugary fizzy drinks, people don’t need that excessive amount of calories and sugar. If you’re switching to sparkling water with lemon, or something like kombucha, you’re getting a flavoursome drink, but without as much sugar and as many of the additives and flavourings.” 2. Processed red meats such as bacon and salami Replace with: White meats like turkey and chicken or fish Nichola says: “A lot of processed red meats can be high in saturated fat and salt. Swap them for white meats like turkey and chicken or, even better, fish. Or you could buy breaded chicken – try to go for products which are 100 per cent chicken fillet and just a bit of bread coating.” 3. Sweets Replace with: Dark chocolate or dried fruit and nuts Nichola says: “Sweets should only be an occasional item. You can switch to a dark chocolate with maybe three ingredients, and then a smaller amount will hopefully be more satisfying. Even better, pair it with a handful of dried fruit and nuts, and yogurt and berries as a snack, so you’ve still got that sweet hit but you’re also getting a lot of healthy fats, antioxidants and vitamin C.” 4. Packaged breakfast cereals Replace with: Porridge Nichola says: “Porridge is great, or even overnight oats. You can pimp it up with some fruit and nuts to boost the fibre and nutrient intake. If you want cereal, opt for a wholegrain version like Weetabix.” 5. Crisps Replace with: Popcorn Nichola says: “You could replace the likes of Pringles with non-UPF crisps like Kettle chips, which are literally just potatoes, oil and salt, and that may help with portion control. But even better is to go for popcorn, because that’s a whole grain, and a great simple swap.” 6. Chocolate Replace with: Nakd bars or Jordan’s cereal bars Nichola says: “Go for snacks with whole foods near the top. Nakd bars are great because they’re literally just dried fruit, nuts and a bit of natural flavouring. Jordan’s bars are based on oats and dried fruit.” 7. Packaged white bread Replace with: Wholemeal or sourdough Nichola says: “You want to avoid the breads that have added sugar in them. If you can, go for wholemeal or ones with just a handful of ingredients like Jason’s sourdough.”