The study, which was published in the journal Cell Metabolism, discovered that people gain more weight on an ultra-processed diet compared to a minimally processed diet, even when they eat the same number of calories.
Conducted by an international team of scientists, the study revealed that a high in ultra-processed foods introduces higher levels of pollutants that are known to affect sperm quality.
“Our results prove that ultra-processed foods harm our reproductive and metabolic health, even if they’re not eaten in excess,” said lead author Jessica Preston, who carried out the research during her PhD at the University of Copenhagen’s NNF Center for Basic Metabolic Research.
“This indicates that it is the processed nature of these foods that makes them harmful.”
To reach these conclusions, the scientists compared the health impact of unprocessed and ultra-processed diets on the same person. This involved recruiting 43 men aged 20 to 35, who spent three weeks on each of the two diets, with a three-month ‘washout’ period in between.
The men were split into two groups, with one group starting on a UPF diet and the other on an unprocessed diet. Half of the men also received a high-calorie diet with an extra 500 daily calories, while half received the normal amount of calories for their size, age and physical activity levels.
Men gained around 1kg more of fat mass while on the UPF diet compared to the unprocessed diet, regardless of whether they were on the normal or excess calorie diet. Several other markers of cardiovascular health were also affected.
The scientists also noted an increase in the level of the hormone-disrupting phthalate cxMINP in men on the ultra-processed diet. Men on this diet also saw decreases in their levels of testosterone and follicle-stimulating hormone, which are crucial for sperm production.
“We were shocked by how many body functions were disrupted by ultra-processed foods, even in healthy young men,” added senior author Professor Romain Barrès, from the University of Copenhagen’s NNF Center for Basic Metabolic Research and the Université Côte d’Azur.
“The long-term implications are alarming and highlight the need to revise nutritional guidelines to better protect against chronic disease.”
