After the watershed: A McDonald’s burger Copyright GETTY IMAGES NORTH AMERICA/AFP SCOTT OLSON
New research finds that ultraprocessed foods lead to increased weight, disrupt hormones and introduce harmful substances linked to declining sperm quality. This means, not all calories are equal and this infers that ultraprocessed foods harm men’s health.
Specifically, men who eat large quantities of ultraprocessed foods gain more fat compared to those eating unprocessed meals, even with equal calories present in the foods consumed. Male hormone levels shift in worrying ways, with testosterone falling and pollutants rising.
People gain more weight on an ultraprocessed diet (foods containing emulsifiers, colourings or preservatives), when compared to a minimally processed diet, even when they eat the same number of calories.
Processed foods are a combination of whole foods – such as fruits, vegetables, nuts and eggs – and processed culinary ingredients.
Scientists say the processing itself, not overeating, is to blame for the observed effects.
According to lead researcher Jessica Preston (University of Copenhagen): “Our results prove that ultraprocessed 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.”
Illhealth effects
A 2024 study in the British Medical Journal– based on information from 9.9 million people worldwide – linked uktraprocessed foods to:
- a higher risk of death from cardiovascular illnesses (such as heart attack and stroke)
- obesity
- type 2 diabetes
- sleep problems
- anxiety and depressio
Methodology
To obtain the best possible data, the scientists compared the health impact of unprocessed and ultraprocessed diets on the same person. The researchers recruited 43 men aged 20 to 35, who spent three weeks on each of the two diets, with three months ‘washout’ in between. Half started on the ultraprocessed and half started on the unprocessed diet. Half of the men also received a highcalorie diet with an extra 500 daily calories, while half received the normal amount of calories for their size, age and physical activity levels.
The subjects were not told which diet they were on. Both the unprocessed and ultraprocessed diets had the same amount of calories, protein, carbs and fats.
In terms of the outcomes, men gained around 1 kg more of fat mass while on the ultraprocessed 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.
What is ultraprocessed food?
There is no single definition of ultraprocessed foods, but in general they contain ingredients not used in home cooking. Many are chemicals, colourings and sweeteners, used to improve the food’s appearance, taste or texture.
In addition, the scientists also discovered a worrying increase in the level of the hormonedisrupting phthalate cxMINP, a substance used in plastics, in men on the ultraprocessed diet.
Men on this diet also saw decreases in their levels of testosterone and folliclestimulating hormone, which are crucial for sperm production.
Implications
The longterm implications are alarming and highlight the need to revise nutritional guidelines to better protect against chronic disease.
Research paper
The findings appear in the publication Cell Metabolism, titled “Effect of ultraprocessed food consumption on male reproductive and metabolic health.”
