In 2026, Tesco gave the “ultra-processed” debate a number shoppers could hold on to: 114. That was how many additives the supermarket said were covered by its own-brand policy—some banned outright, others restricted. Its suppliers were asked to begin with familiar “kitchen cupboard” ingredients and use additives only when safety, shelf life or quality required them. Alice Ritchie, Tesco's head of healthy and sustainable diets, said customers wanted fewer processed foods but found the subject hard to navigate.1,2
The rule changes real recipes. It can remove an artificial colour from an own-brand product. It can restrict a sweetener or send a supplier back to the recipe bench. Yet the product does not become unprocessed. Nor does the rule show whether the food is high in salt or low in fibre. It cannot show whether it helps with an allergy, adds a needed nutrient or costs little enough to eat often. An additive list and the term “ultra-processed” are doing different jobs.
That difference matters because Hall's controlled study tested two whole diets, not a list of additives. At the US National Institutes of Health, Kevin Hall and his colleagues brought 20 adults into a clinical ward for a continuous 28-day stay. Each person spent two weeks with an ultra-processed menu and two weeks with an unprocessed menu, in random order. They could eat as much or as little as they liked.4
On the ultra-processed menu, the participants ate an average of 508 more calories a day and gained about 0.9 kilograms. During the unprocessed period, they lost about 0.9 kilograms. The two whole diets had a causal effect over a short period. Yet the result did not point to one guilty additive. It did not prove long-term disease or make every packaged loaf, ready meal and tin of beans equal.4
A category made to measure a dietary shift
“Ultra-processed” did not begin as a warning sticker. In 2010, Carlos Monteiro and colleagues at the University of São Paulo published a new way to classify food. Instead of sorting it mainly by nutrients or familiar food groups, they sorted it by the extent and purpose of industrial processing. Their first version had three groups, and they applied it to food-availability data from 48,470 Brazilian households.3
The framework later grew into the four groups now known as NOVA. The first covers unprocessed or lightly processed foods. The second covers cooking ingredients such as oils or sugar. The third covers processed foods made by combining those groups. The fourth covers ultra-processed recipes. These products are built mainly from industrial ingredients, often with additives and little intact whole food.4
This gave researchers a way to follow a change that a nutrient panel could miss. Monteiro's first household analysis found that the share of the most processed group rose with income in Brazil. The system asks what happens as industrial recipes replace traditional meals and their ingredients across a diet.3
An additive blacklist cannot reproduce NOVA. Tesco's policy works one ingredient at a time within its own-brand supply chain. NOVA looks at the recipe, processing and purpose of the whole product. A recipe may lose an additive and still belong to NOVA's fourth group. Another packaged food may remain useful because of the role it plays in a person's diet.
Processing also has useful jobs. Heating milk in a set way kills harmful bacteria. Tinning and freezing help food last. Ready meals save time. Hall's paper notes that ultra-processed products can cost less, last longer and be easy to use. They can also be quite safe from microbes.4,7 Tesco's own report shows the same tension. It asks suppliers to use fewer additives while keeping those needed for safety, shelf life and quality.2
The question is not whether processing is simply good or bad. The useful questions are what a process or recipe does and what changes when such products become the base of a diet.
The ward test changed what could be said
Before Hall's experiment, studies could show that people eating more ultra-processed food often had worse health outcomes. They could not easily show whether the food pattern caused the change. Other differences in income, health, activity and diet might travel with it.
Hall's team tried to close one part of that gap. Ten men and ten women lived continuously in the National Institutes of Health clinical centre. The researchers presented two rotating menus designed to be similar in offered calories, energy density, protein, carbohydrate, fat, sugar, sodium and fibre. One menu drew about 81% of its calories from ultra-processed foods; the other drew most of its calories from unprocessed or minimally processed foods. The participants were free to eat more or less.4
The turn came at the table. The participants ate much more energy on the ultra-processed menu, mostly through extra carbohydrate and fat. They rated both menus about the same for taste and familiarity. Yet they ate the ultra-processed food faster. The two whole diets led to different intake and short-term weight results under those conditions.4
Two measured clues stand out. Participants ate the ultra-processed meals faster. The non-beverage foods in that menu were more energy dense, which the authors said likely contributed to excess intake. To sort the possibilities, a new comparison would need to change one feature at a time while holding the others steady. The menus were matched on several measures. Even so, they differed in added sugar, types of fibre and types of fat. Texture, eating speed, energy packed into the food, the recipe and food structure may work together. A longer comparison that split those features apart could change the explanation. Until then, the effect cannot be pinned on one additive or one processing step.
The practical conditions differed too. Hall's team estimated that ingredients for 2,000 calories a day cost $106 a week for the ultra-processed menu and $151 for the unprocessed menu at the local supermarket used for the sum.4 The figures are not a current UK shopping budget. They still show why “just replace everything” is not a full answer. Time, storage, cooking space, price and access shape what can become routine.
Different foods do not carry the same evidence
A shopper can hold two questions at once: what happened in Hall's ward, and what happens over years of ordinary eating. The second question is harder because money, health, activity and diet move together.
The UK's Scientific Advisory Committee on Nutrition reviewed the wider evidence. It found consistent and concerning associations between higher consumption of ultra-processed food and outcomes including obesity, type 2 diabetes and cardiovascular disease. That concern comes after the controlled trial result, not instead of it.5
Why the long-term answer is harder
The long-term evidence was still almost all based on watching what people ate and what happened later. Such studies handled income, body weight, energy intake and other diet factors in uneven ways. That leaves room for confounding, where a third factor is tied to both the food and the health result. The committee could not say how much of the observed risk came from processing itself. Some could come from known risks such as excess calories, saturated fat, salt, free sugars or processed meat.5
This investigation continues below.
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The category breaks apart on the shelf
Nor did every part of the group move together. Meat products and sweetened drinks were among the groups more often linked with poor outcomes. Results for breads, cereals, dairy foods, snacks, sauces and ready-to-eat foods were mixed. Vegetarian alternatives were not linked with poor outcomes in the smaller group studies that SACN reviewed.5
What would change the conclusion
The gaps do not offer an all-clear. The controlled result supports concern about a diet that led people to eat more. Wider links point the same way for several key outcomes. The open issue is how much each factor matters over the long term: processing, nutrients, food structure, certain recipes or the social setting. Evidence that separated those factors and showed no separate processing effect would narrow the case. Evidence of lasting effects from set features would sharpen it. Neither result covers the whole group today.
Why the number 114 still leaves people unsure
Tesco's move responds to a genuine wish for something easier to use. The retailer said more than 80% of its customers were trying to eat fewer processed foods but found the issue hard to navigate. Its published rule offers a concrete signal: selected additives will disappear or face restrictions in own-brand recipes.1,2
But a signal can become a shortcut. A product with a shorter, more familiar list may still be high in salt, saturated fat or sugar. An unfamiliar ingredient may help keep food safe from microbes. It may also help food last. The ingredient list cannot carry the whole judgement.2
The confusion is not confined to one supermarket. In a year-long public dialogue, UK Research and Innovation brought 132 people through six workshops and more than 20 hours of discussion. Participants expressed concern about additives and distrust of marketing, but they also pointed to affordability and availability. Some said meaningful choice was especially constrained in places where healthier options were harder to find or pay for.6
Those talks do not prove a health effect. They show why a simple label can feel attractive while leaving the choice unresolved. A household does not eat a classification. It eats meals shaped by money, time, health needs, taste and access.
A better test for the food in front of you
The most useful first move is not to purge every packaged food. Start with products where the evidence and diet advice already agree. Cut back on sugary drinks and sweets. Do the same with frequent snacks or meals high in calories, saturated fat, salt or sugar and low in fibre. At home and when shopping, make fruit, vegetables, pulses and wholegrain or higher-fibre staples the usual base for meals when price, time, health and access allow. This applies that direction without claiming that “natural” always means healthy.5,7
For the packaged foods that remain, three questions work better than one blacklist. What role does the food play: daily staple or rare extra? What does the nutrition panel say about calories, saturated fat, salt, sugar and fibre? What does the recipe add, remove or make possible? That may include protecting food from spoilage, adding nutrients, meeting allergy needs or saving time.
The National Health Service makes room for this distinction. It notes that wholemeal sliced bread, wholegrain or higher-fibre breakfast cereals and baked beans can be part of a healthy diet even when they fall within the ultra-processed category. It also recommends using the nutrition information on packs to compare products.7
Those foods are not healthy by default. Choose intact, familiar foods for their dietary role, not merely because they look natural. When two choices serve the same dietary role and are equally useful, favour recognisable natural inputs. Natural inputs are the preference; how a pack breaks down after use is a separate question. Food safety, nutrition and packaging remain separate questions. Make intact, familiar foods the steady base where possible. Ask more of industrial recipes. Keep a useful staple when a more “natural” food has less value, does not meet an allergy need, costs too much or is not available.
Back at the Tesco shelf, the number 114 shows that a supplier rule has changed. It cannot show how much food a person will eat. Nor does it show what else is in the meal or what a swap will cost. The controlled trial makes the concern hard to dismiss. Under its conditions, people ate more and gained weight on the ultra-processed menu. The next choice is more precise than accepting or rejecting a whole group. Change the repeat foods most likely to drive that pattern. Then judge the packaged foods you need by their role, nutrition and recipe together.