Ultra-processed foods linked to weight gain, hormone disruption and lower sperm quality in men

International scientists speculate that the rise of ultra-processed foods (UPFs) is linked to a diversity of poor health outcomes in men, highlighting that rates of obesity and type-2 diabetes have soared, while sperm quality has plummeted over the past 50 years.

The study revealed that men gained more weight on ultra-processed meals than on minimally processed foods, even when both diets contained the same number of calories.

Additionally, it flags that diets high in ultra-processed foods expose consumers to higher levels of plastic-based pollutants that may impact sperm quality.

However, the researchers cannot confirm whether these impacts are attributed to the industrial nature of the food ingredients themselves, the processing of the foods, or because they lead people to eat more than they should.

“Our results prove that ultra-processed foods harm our reproductive and metabolic health, even if they’re not eaten in excess. This indicates that it is the processed nature of these foods that makes them harmful,” says Jessica Preston, lead author of the study, who carried out the research during her PhD at the University of Copenhagen’s NNF Center for Basic Metabolic Research (CBMR), Denmark.

Ultra-processed weight gain

The researchers cross-examined the health impact of unprocessed and ultra-processed diets on each individual. Their study involved 43 male participants aged 20 to 35, who spent three weeks on each of the two diets, with a three-month “washout” period in between.

Half of the group began with the ultra-processed diet, while the other was assigned an unprocessed diet.

The participants were not informed which diet they were assigned. Both the unprocessed and ultra-processed diets had the same amount of calories, protein, carbs, and fats.

Additionally, 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.

Regardless of whether they were on the normal or excess calorie diet, participants fed ultra-processed foods gained around 1 kg more of fat mass compared to the unprocessed diet.

In terms of metabolism, participants’ daily energy intake was approximately 500–800 kcal higher when consuming ultra-processed foods compared to an unprocessed diet. However, it’s still unclear if the negative health effects are solely from the extra calories or if the foods are inherently harmful.

Exposure to endocrine disruptors

The study published in Cell Metabolism warns of a “worrying increase” in the amounts of the hormone-disrupting phthalate cxMINP — a substance used in plastics — in men on the ultra-processed diet.

Men on this diet also recorded lower levels of testosterone and follicle-stimulating hormone, which are crucial for sperm production.

Surprisingly, when participants switched over to an unprocessed diet, they exhibited a short-term increase in inflammation.

The researchers believe this happened because the participants were already lean and used to a diet with many UPFs. The sudden change to an unprocessed diet may have triggered a temporary stress response, causing this unusual inflammatory reaction.

“We were shocked by how many body functions were disrupted by ultra-processed foods, even in healthy young men,” says the study’s senior author, professor Romain Barrès from the University of Copenhagen’s NNF Center for Basic Metabolic Research and the Université Côte d’Azur, France.

“The long-term implications are alarming and highlight the need to revise nutritional guidelines to better protect against chronic disease.”

Nuance is needed in UPF research

UPF consumption has been linked to a range of negative health outcomes independent of caloric intake. Investigations into this topic have highlighted their potential links to overall weight gain, early-onset Parkinson’s disease, and increased intramuscular fat content.

However, experts urge a more nuanced approach to investigating the effects of UPFs, warning against blanket regulatory policies restricting their consumption. They advocate more emphasis on avoiding nutrient-poor UPFs in dietary guidance, rather than avoiding all types of UPFs.

The Physicians Committee for Responsible Medicine cautions that few US consumers can identify healthy UPFs, with 39% of poll respondents believing all types of processed foods are unhealthy.