Group 1
Unprocessed
Whole ingredients in roughly the form you'd find them in nature.
eggs · tomatoes · oats · chicken · lentils
The science behind the score
Group 1
Whole ingredients in roughly the form you'd find them in nature.
eggs · tomatoes · oats · chicken · lentils
Group 2
Extracted or refined for cooking. Not really eaten alone.
olive oil · flour · butter · salt · sugar
Group 3
Group 1 ingredients preserved or transformed using Group 2 ingredients.
tinned fish · aged cheese · cured meats · sourdough
Group 4
Industrial formulations containing additives with no culinary equivalent.
protein bars · shop-bought bread · flavoured yoghurts
Key finding - Hall et al., NIH 2019
Two diets matched for calories, macros, fibre, and sugar on paper. The ultra-processed arm still consumed around 500 extra calories per day and gained weight.
Same nutrient profile, very different outcomes. The question is not only what is in a food, but what has been done to it.
What researchers think is happening
Whole foods have physical structure - cell walls, fibre networks, water content - that slows absorption and signals fullness. Industrial processing dismantles this.
Some emulsifiers and preservatives have been shown to disrupt gut bacteria populations and gut lining integrity. The human evidence is still developing, but the pathway is credible.
Foods engineered to hit precise fat, salt, sugar, and texture combinations can override normal satiety feedback loops. Not a willpower failure - a calibration problem.
Ultra-processed foods tend to be softer, pre-broken-down. People eat them faster - outpacing the hormonal signals that register fullness.