Even in young healthy men, the damage was widespread and measurable
A study from the University of Copenhagen quietly challenges one of nutrition's oldest assumptions: that a calorie is a calorie, and a nutrient a nutrient, regardless of how food arrives on the table. Forty-three young men, fed identical calories from radically different sources, revealed that industrial processing itself carries a biological cost — one that touches fat, hormones, and the very machinery of reproduction. The findings are modest in scale but pointed in direction, adding weight to a growing suspicion that what we have done to food may be quietly undoing something in us.
- Even when calories and nutrients were perfectly matched, men eating ultraprocessed foods gained fat and accumulated hormone-disrupting chemicals in their blood and semen.
- Testosterone and the hormone responsible for sperm production both dropped measurably during the ultraprocessed phase, raising quiet alarms about male reproductive futures.
- The lead researcher described being 'shocked' by how broadly bodily functions were affected — not in sick men, but in young, healthy ones.
- Scientists are now pressing for nutritional guidelines to be rewritten, arguing that current frameworks ignore the biological cost of industrial food processing itself.
- The study's small size and short duration leave the door open for doubt, but researchers frame these results as a signal demanding larger, longer investigation.
Researchers at the University of Copenhagen asked a deceptively simple question: does industrial food processing harm the body even when calories and nutrients remain identical? Their answer, drawn from 43 young men over three months, was unsettling — yes, and the damage reaches further than most expected.
Participants alternated between two carefully matched diets. One drew 77 percent of its calories from ultraprocessed foods — the engineered, additive-laden products that fill supermarket shelves. The other relied on minimally processed whole foods. The calorie counts were the same. The nutritional profiles were the same. What changed was the source.
Three harms emerged from the ultraprocessed phase. The men gained roughly a kilogram of fat on average. Their blood levels of a plastic-related chemical known to disrupt hormonal function rose noticeably, suggesting contaminants were entering the body through the food or its packaging. Most strikingly, both testosterone and follicle-stimulating hormone — essential for sperm production — declined significantly.
Lead researcher Romain Barrès said he was shocked by how many bodily systems were affected, even in healthy young men. His colleague Jessica Preston added that harm appeared even at moderate consumption levels, not just in excess. Together, they are calling for nutritional guidelines to be reconsidered in light of what industrial processing itself may cost the body.
The study is small, short, and limited to men — its authors are the first to acknowledge it is not a final verdict. But it joins a growing body of evidence suggesting that how food is made may matter as much as what it contains, and that the long-term price of ultraprocessed diets remains largely uncounted.
Researchers at the University of Copenhagen set out to answer a deceptively simple question: does the industrial processing of food harm your body even when the calories and nutrients stay the same? What they found in 43 young men suggests the answer is yes—and the damage runs deeper than weight gain alone.
The study recruited healthy men between 20 and 35 years old and had them follow two different diets over a three-month period, then switch. Both diets were carefully balanced for calories and nutritional content. The difference was in the source: one diet drew 77 percent of its calories from ultraprocessed foods—the kind of industrial formulations you find lining supermarket shelves, engineered from extracted ingredients and chemical additives rather than whole foods. The other diet consisted mainly of unprocessed or minimally processed foods, the kind that arrive at your table much as they came from the earth.
When the men ate the ultraprocessed diet, three measurable harms emerged. First, they gained roughly a kilogram of fat mass on average, despite the calorie count being identical to the unprocessed alternative. Second, their blood levels of a plastic-related chemical called cxMINP rose noticeably. This substance is known to interfere with hormonal function—a finding that troubled the researchers because it suggested the men were accumulating contaminants from the food itself or its packaging. Third, and perhaps most concerning, their testosterone levels and follicle-stimulating hormone—the hormone essential for sperm production—both declined significantly.
Romain Barrès, the molecular biologist leading the work, expressed surprise at the breadth of the damage. "We were shocked at how many bodily functions were affected by ultraprocessed foods, even in young healthy men," he said. The implications, he added, are alarming over the long term and suggest that nutritional guidelines need rethinking to protect against chronic disease. Jessica Preston, a nutritionist at the same institution, underscored the point: the research shows that ultraprocessed foods harm reproductive and metabolic health even when consumed in moderate amounts, not just in excess.
It is worth noting what the study does not claim. Forty-three men is a small sample. Three months is a short window. The research involved only men, leaving questions about whether women experience similar effects. The findings are not a final word but rather a signal—one more piece of evidence in a growing body of research suggesting that how food is made matters as much as what it contains. The researchers are calling for a broader reassessment of how much ultraprocessed food we eat and what the long-term cost might be.
Citas Notables
We were shocked at how many bodily functions were affected by ultraprocessed foods, even in young healthy men.— Romain Barrès, molecular biologist, University of Copenhagen
Ultraprocessed foods harm reproductive and metabolic health even when not consumed in excess.— Jessica Preston, nutritionist, University of Copenhagen
La Conversación del Hearth Otra perspectiva de la historia
Why does it matter that the calories were the same? Couldn't the weight gain just be from eating more?
That's the whole point—they weren't eating more. The calories were matched precisely. So the fat gain happened not because of excess energy but because of something in the ultraprocessed food itself, or how the body processes it differently.
And the plastic chemical—how does that get into the food?
It's likely in the packaging or leaches from it during storage and handling. But the fact that it accumulated in their blood and semen suggests the body isn't clearing it out the way it should.
The hormone drops—is that reversible?
The study doesn't say. They switched diets after three months, but we don't know if testosterone bounced back or how long recovery took. That's a crucial gap.
Why focus on men specifically?
Reproductive health is easier to measure in men—sperm count, hormone levels. But the researchers were probably also interested in whether ultraprocessed foods affect fertility and sexual function, which matters for public health.
Does this mean I can never eat processed food?
No. The study looked at 77 percent of calories from ultraprocessed sources—that's an extreme diet. The real question is where the threshold is. How much is safe? We don't know yet.
What would you want to see next?
A longer study. More diverse populations. And research on whether the damage is reversible or permanent. Also, we need to understand which specific additives or processing methods cause the most harm.