Junk food’s unhealthiness may stem from its soft texture, not just fat and sugar, according to new research that shifts the focus from what is in ultra‑processed foods to how they are eaten.
Ready meals, snacks and other processed items have long been vilified for their high levels of fat, sugar and artificial ingredients. But scientists now believe the real problem could be that their soft, easy‑to‑chew texture encourages people to eat far more calories before their bodies register fullness. This, they argue, may explain why those who consume a lot of ultra‑processed food (UPF) tend to be more overweight, a condition that worsens a host of health problems.
The texture theory
Professor Ciarán Forde, a food scientist at Wageningen University in the Netherlands who led the research, said: “If you have softly textured, energy‑dense foods that are very easy to consume, then by the time you realize you’ve over‑consumed, it’s too late.”
UPF is defined as food that has been altered or processed in any way. The category includes items often considered relatively healthy, such as sliced bread, breakfast cereals, pre‑prepared sauces and flavoured yoghurts, as well as the obvious biscuits, crisps and ready meals.
‘Slow’ vs ‘fast’ UPF: the study explained
To test the theory, Forde and his colleague Professor Marlou Lasschuijt designed two different UPF diets that were broadly similar in nutritional composition but engineered to encourage different eating speeds. The trial involved 41 Dutch participants who were given all their meals and snacks for two weeks on one diet, then, after a break, switched to the other for a further two weeks. Crucially, they could eat as much as they wanted of the provided foods.
The typical menus illustrate the difference. On the “slow” UPF diet, breakfast consisted of yogurt with high‑fibre cereal and fruit chips; lunch was a cheese sandwich made with multigrain bread; dinner featured smoked chicken breast slices, a prepared mixed salad and pre‑cooked flavoured rice. In contrast, the “fast” UPF diet offered a fruit smoothie and brioche for breakfast, a cheese sandwich with soft bread for lunch, and a ready‑meal meat stew with mashed potatoes for dinner.
The results were striking. While on the “slow” diet, participants consumed an average of 370 fewer calories per day than when eating the “fast” diet. For context, the typical recommended daily intake is around 2,000 calories.
“Energy intake rate influences the amount of calories that we consume in a meal,” said Lasschuijt, who also ran the trial. She presented the findings at the British Nutrition Foundation’s conference last week, titled “Beyond the UPF Debate”.
The study suggests that the speed of eating is a powerful driver of overconsumption. When food is soft and quickly swallowed, the brain has less time to register satiety signals, leading to a higher calorie load before the body feels full.
Practical advice: simple swaps, not total abstinence
Despite the focus on texture, the researchers stress that people do not need to eliminate all processed food from their diets. Forde pointed out that the meals in the “slow” diet “were not specially constructed foods – these are foods from the local supermarket. We just looked at how they were eaten rather than what was in them.”
Professor James Stubbs, a biopsychologist at the University of Leeds who was not involved in the study, said more research is needed into which “slower‑eating” foods have the most appeal. “Understanding this in a more nuanced way would help us steer people towards the more textured foods that are slower foods, and are better for weight management,” he said.
Forde offered a straightforward takeaway: “You don’t have to go out of your way to make every food you eat incredibly crunchy and dry and unpleasant and thick and chewy and hard.” Pointing to the foods used in his trial, he added: “There are very simple swaps that people can make that can actually change the way they eat and slow it down.”
He cautioned, however, that food texture and eating rate are unlikely to be the only factors that make UPF less healthy. “I would never say there’s a single cause for something as complicated as human behaviour.”