Cellophane-wrapped bread, strawberry-flavored yogurt, whole grain breakfast cereal, protein snack bars, gummy bears, hot dog sausages, supermarket cupcakes, microwave lasagne… The list of ultra-processed foods (UPFs) goes on and on.
Any food made industrially, with ingredients or techniques you wouldn't find in a home kitchen, is technically UPF. In the UK and US, that's more than half of the average person's diet.
Eating more of this food is associated with a higher risk of obesity, type 2 diabetes, heart disease and various cancers. If you glance at a ready meal's long ingredients list, you might assume that all its unfamiliar additives are the main reason why.
You're not totally misguided. Some chemicals added to UPFs may lead to poorer health outcomes — certain food dyes are linked with hyperactivity in children, some preservatives in processed meat with heightened cancer risk, and specific emulsifiers may damage the gut microbiome.
Clearly, that's a problem — but it's not the whole story. Increasingly, scientists are pointing to a less obvious culprit: texture.
Prof Sarah Berry, nutrition scientist at King's College London, says the real issue with ultra-processed food isn't just the additives and emulsifiers. "Ultra-processed food generally has had its texture changed so it's very soft," she explains. The result: you eat it more quickly, and end up eating more of it.
In a landmark study led by nutrition scientist Kevin Hall, 20 participants ate either a minimally or ultra-processed diet for two weeks, then switched. Meals were nutritionally matched, and participants could eat as much as they liked.
When eating the ultra-processed meals, participants consumed an average of 500 extra calories per day — mainly from fat and carbs — and gained almost 1kg of weight. One major difference stood out: they ate ultra-processed meals more quickly.
"We've been able to show for years now that eating faster means you're going to consume more energy," says Prof Ciarán Forde of Wageningen University. Speeding up eating by 20 percent, his research shows, leads to consuming 11 – 15 percent more calories.
Forde explains that the first phase of digestion begins in the mouth, not the stomach. How you chew influences how you digest your meal and how full you feel afterward. If food is so soft you barely need to chew — like many UPFs — you can eat a large portion before your brain signals fullness.
This led Forde to test two diets, both 95 percent ultra-processed, but differing in texture. One featured chewier, crunchier foods; the other softer, spongier foods. People ate around 370 fewer calories on the slower, chewier diet and gained less body fat.
Large observational studies back this up: not all UPF categories are equally harmful. Notable exceptions include whole grain bread, flavored yogurt and breakfast cereals.
Forde cautions against treating all UPFs as equally bad, calling such conclusions a misreading of the research. The focus, he argues, should be on soft, energy-dense foods eaten quickly — and swapping them for equally enjoyable options that take longer to eat. That way, you can enjoy the pleasure of eating and feel satisfied, without the guilt.