Scientists have long known that people who eat lots of ultra-processed foods face higher risks of heart disease, type 2 diabetes, and some cancers.
The missing piece has been understanding exactly what these foods do inside the body.
A new study suggests the answer may be written in our blood. People who eat the most ultra-processed foods carry a distinct chemical fingerprint that points to disrupted fat metabolism and greater stress on their cells.
The findings offer one of the clearest biological explanations yet for why diets built around packaged, industrially made foods are linked to so many chronic diseases.
Linking diet to blood
For years, scientists have linked diets high in packaged, industrially made foods to poor health without fully understanding what happens between the meal and the illness.
Jessica Blanco-Lopez, a researcher at the International Agency for Research on Cancer (IARC) in France, set out to close that gap.
Her team analyzed blood samples and diet records from 15,200 people enrolled in a long-running European study.
Researchers classified each participant’s diet using the Nova system. This widely used scale ranks foods by their level of processing, from fresh ingredients to ultra-processed products made largely with industrial additives.
The researchers measured hundreds of small molecules in each blood sample, looking for chemical signatures that rose or fell with ultra-processed food intake.
This is the first study to use targeted metabolomics – a method that measures specific known molecules in the body – to examine these diets in such a large European population.
Earlier research linked ultra-processed diets to heart and blood vessel disease, but the chemical pathway connecting these foods to illness remained unclear.
The body’s warning signs
The diet left its mark on 22 different metabolites, the intermediate and end products the body makes as it breaks food down.
Those who ate the most stood apart. Their blood held more of certain fatty by-products that build up when cells cannot burn fat properly, a sign that the energy-making machinery inside cells is faltering.
At the same time, several fats the body relies on were running low. These lipids help build cell membranes and pass signals between cells, and their drop suggests the normal handling of fat is being knocked off balance.
Put together, the reading suggests two problems at once. The body appears to be making more of its own fatty compounds, including cholesterol, while doing a worse job of processing fat the healthy way.
The pattern hints that these foods do harm on two fronts, both by crowding better options off the plate and by disturbing metabolism itself.
“UPF consumption may contribute to health risks through nutritional displacement and inducing metabolic disruption,” said Dr. Blanco-Lopez.
Healthy fats start shifting
The blood also carried a telling mix of eight fatty acids. Chief among them was stearic acid, a saturated fat that climbs with a rich diet or when metabolism runs into trouble, sitting alongside unusually high levels of long-chain fats of a very different type.
That combination told the researchers something the food labels could not. The extra fat did not all come from what people ate.
The rest, it seemed, was made by the body itself from surplus carbohydrates, the refined sugars and starches packed into many products.
The finding does not stand alone. A study of thousands of British children found that heavy eaters carried their own blood signature of altered fats, one tied to gaining body fat as they grew.
Traces of industrial fats lingered too, even when intake was low.
Association, not causation
The study cannot prove that ultra-processed food caused these changes. It captured each person at a single point in time rather than following them for years, so it shows a strong association, not cause and effect.
Dr. Blanco-Lopez and her colleagues tested their findings several ways before trusting the results. That careful approach paid off.
“What was particularly reassuring was that, despite these different approaches, the results remained remarkably consistent,” said Dr. Blanco-Lopez.
What the study adds is a clear biological explanation. Until now, the harms linked to ultra-processed diets were mostly reflected in population statistics.
The blood signature suggests the body is under two kinds of stress at once, producing more fat than it should while weakening its ability to protect cells.
Blood may predict disease
Other researchers have already begun linking these blood patterns to disease. One study found a diet-related chemical signature linked to higher rates of mental health disorders beyond diet surveys alone.
That gives the metabolic fingerprint practical value because it could one day help doctors detect metabolic damage before symptoms appear.
The next step is to track these blood signatures over time to determine whether the chemical changes appear before disease develops.
The findings suggest that diets that stay away from ultra-processed foods leave a healthier signature in the blood. They also help keep the fats that support normal cell function where they belong.
The study is published in Critical Reviews in Food Science and Nutrition.
—–
Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.
—–