Does the harm come from the calories or the processing itself?
A key experiment directly tested this question. In a controlled crossover trial, participants ate either an ultra-processed or an unprocessed diet for a set period, with the same total calorie intake in both phases [4]. Even when calories were matched, the ultra-processed diet led to a significant increase in body weight and a worse LDL-to-HDL cholesterol ratio—a key marker of heart disease risk [4]. This means the processing itself, not just overeating, damages metabolic health.
The same trial also found that ultra-processed foods altered hormones involved in energy metabolism and reproduction, and increased levels of a phthalate (a chemical linked to metabolic disruption) in the blood [4]. These effects occurred regardless of whether participants ate more calories or not, confirming that the food's composition and additives matter independently.
What specific metabolic harms are linked to ultra-processed foods?
Ultra-processed foods are tied to multiple metabolic problems beyond weight gain. In a study of over 36,000 Brazilian adolescents, those who ate the most ultra-processed foods (top third of intake, ≥38.7% of daily calories) had significantly higher LDL cholesterol (the 'bad' cholesterol) and lower HDL cholesterol (the 'good' cholesterol) compared to those who ate the least [2]. This pattern held even after adjusting for other factors like total calorie intake and physical activity.
Another large study tracked 3,751 adults for 23 years and identified 12 blood metabolites linked to ultra-processed food consumption [1]. Three of these—mannose, glucose, and a marker called N2,N2-dimethylguanosine—were associated with a higher risk of developing chronic kidney disease over time [1]. These metabolites reflect disrupted metabolism, not just extra calories.
A comprehensive review of over 100 studies concluded that a diet high in ultra-processed foods increases the risk of multiple chronic diseases, including type 2 diabetes, cardiovascular disease, and metabolic syndrome, through mechanisms like high energy density, altered food texture, and harmful additives [3].
Could some ultra-processed foods be beneficial?
A few studies have suggested that certain ultra-processed subgroups—like whole-grain breads or breakfast cereals—might be linked to lower diabetes risk when they replace other ultra-processed items [5]. However, experts caution that these findings are unreliable for several reasons: the consumption of these specific foods was very low (often less than 1% of total intake), the analyses are prone to statistical errors, and the overall body of evidence shows that ultra-processed foods as a category are harmful for 32 different health outcomes [5]. The safest conclusion is that replacing any ultra-processed food with a minimally processed alternative is better for metabolic health.
About These Sources
This answer is built on 5 peer-reviewed studies — published from 2023 to 2025, 3 from 2024 or later, 4 in Q1 journals, collectively cited 95 times — selected as the most relevant from 6 studies that passed quality screening, drawn from 45 papers retrieved from a database of over 500 million.
Sources used in this answer
Metabolomic Markers of Ultra-Processed Food and Incident CKD
In a cohort of 3,751 adults followed for 23 years, 12 blood metabolites were identified as markers of ultra-processed food intake; three of these (mannose, glucose, and N2,N2-dimethylguanosine) were associated with higher risk of incident chronic kidney disease, suggesting metabolic harm beyond calories.
Consumption of ultra-processed foods and cardiometabolic risk factors in Brazilian adolescents: results from ERICA
Among 36,952 Brazilian adolescents, those in the top third of ultra-processed food intake (≥38.7% of daily calories) had significantly higher LDL cholesterol and lower HDL cholesterol, along with poorer diet quality (more sodium, saturated fat, less fiber and protein), independent of total energy intake.
Ultra-processed foods and human health: the main thesis and the evidence
A comprehensive review combining narrative and systematic analyses concluded that ultra-processed food consumption displaces whole-food diets, degrades diet quality, and increases risk of multiple chronic diseases through mechanisms including high energy density, hyper-palatability, and harmful additives—independent of calorie intake.
Effect of ultra-processed food consumption on male reproductive and metabolic health
In a controlled crossover trial, an ultra-processed diet increased body weight and LDL-to-HDL cholesterol ratio compared to an unprocessed diet, even when calorie intake was matched; it also altered metabolic hormones and increased a phthalate metabolite in the blood, showing harm independent of caloric load.
Are all ultra-processed foods bad for health?
Commentary on subgroup analyses of ultra-processed foods notes that while some specific items (e.g., whole-grain breads) appear protective against diabetes in some studies, these findings are unreliable due to very low intake levels, statistical issues, and the overwhelming evidence that ultra-processed foods as a category are harmful for 32 health outcomes.