80% of What's in Your Trolley Isn't Really Food
Dr Chris van Tulleken ate nothing but ultra-processed food for a month. His brain changed, his hormones shifted, and he gained 6.5kg. Here is what he found - and what it means for your weekly shop.
Dr Chris van Tulleken is an infectious diseases doctor at University College London. He's also one of the BBC's most recognisable science presenters. In 2023, he published Ultra-Processed People, which became a Sunday Times bestseller and changed how a lot of people look at their shopping baskets. But the book didn't come from desk research alone - it came from a personal experiment that went further than he expected.
For one month, van Tulleken ate a diet composed of 80% ultra-processed food. That sounds extreme until you realise it's close to the average UK and Irish diet already.
What Counts as Ultra-Processed
The NOVA classification system, developed by researchers at the University of São Paulo, divides food into four categories. Group 1 is unprocessed or minimally processed - an apple, a piece of chicken, a bag of oats. Group 4 is ultra-processed: industrial formulations made mostly from substances derived from food, plus additives. Think sliced bread with 15 ingredients, breakfast cereals with added vitamins, protein bars, diet drinks, ready meals.
The simplest test van Tulleken suggests: if the product contains an ingredient you wouldn't find in a domestic kitchen - emulsifiers, humectants, flavour enhancers, modified starches - it's likely ultra-processed. You don't need a chemistry degree. You just need to read the back of the packet and ask whether your grandmother would recognise what's listed.
Six corporations control approximately 75% of the calories consumed globally. The food system is not primarily designed around nutrition - it's designed around shelf stability, manufacturing efficiency, and profit margins. [The Lancet, Global Syndemic of Obesity, 2019]
What Happened to Van Tulleken's Body
During his month on ultra-processed food, van Tulleken gained 6.5 kilograms. Brain scans showed new neural connections forming between reward centres - similar to patterns seen in substance addiction. His hunger hormones shifted: the signals that tell you you're full were weakened, while the signals driving appetite were amplified. He reported constant cravings, disturbed sleep, and difficulty concentrating.
When he returned to a whole-food diet, the changes reversed. But the point wasn't that junk food is bad - most people already know that. The point was that ultra-processed food appears to override the body's natural appetite regulation system in ways that unprocessed food, even in large quantities, does not.
The Label Problem
Van Tulleken is particularly sharp on how food labelling systems can inadvertently protect ultra-processed products. The UK's traffic light system - green for low, amber for medium, red for high across fat, salt, sugar, and saturated fat - was meant to help consumers. But a can of Diet Coke gets four green lights. A pot of natural yogurt gets an amber for fat. The system measures individual nutrients without distinguishing between whole foods and industrial formulations.
Companies also routinely add synthetic vitamins and minerals to ultra-processed foods, enabling them to carry health claims like "source of vitamin D" or "high in fibre" on products that would otherwise have no nutritional merit. The fortification doesn't make the product healthy - it makes the marketing legal.
Why It Matters for Your Weekly Shop
The average supermarket in Ireland or the UK dedicates about 60-70% of its shelf space to ultra-processed products. They're cheaper to manufacture, more profitable for retailers, and engineered to be more palatable than whole foods. There's very little profit margin in selling raw broccoli, eggs, or milk - supermarkets sometimes sell basic whole foods at a loss to get people through the door.
That creates an economic reality that individual willpower can't fully solve. But awareness helps. When you know that the "healthy" cereal bar is closer to confectionery than it is to food, you can make a more honest choice. When you know that "protein" slapped on a processed snack doesn't make it nutritious, you save yourself the premium price.
A Practical Filter
Van Tulleken doesn't recommend obsessive label reading. He recommends a single question: could I make this at home with normal kitchen ingredients? If the answer is yes - bread with flour, water, salt, yeast - it's probably fine. If the answer is no - bread with methylcellulose, calcium propionate, diacetyl tartaric acid esters, and soy lecithin - it's ultra-processed, and you're eating an industrial product, not food in any traditional sense.
That doesn't mean never eating it. It means knowing what it is.