Ultra-processed foods are everywhere. For most people, they’re virtually impossible to completely avoid. Whether it’s a quick snack on the go or a convenient restaurant meal, ultra-processed foods are likely lurking within. While we’ve long been aware that these empty calories aren’t good for us, a new study shows just how damaging ultra-processed foods can be to men’s health.

Researchers looked at healthy men, ages 20 to 35, who adhered to two different diets three months apart. One diet consisted of ultra-processed foods and the other of unprocessed, whole foods. Half of the men were also put on a diet consisting of 500 more calories than their counterparts, whose caloric intake was adjusted for size, age and activity levels.

The men on the ultra-processed food diet gained about 1 kilogram more of fat compared with those on the healthier diet. Both the unprocessed and ultra-processed diets had the same number of calories. This helped demonstrate that men’s weight gain was not attributed to overeating, but to the nature of the foods themselves.

Researchers also noted hormonal disruptions among those consuming ultra-processed foods. Levels of testosterone and follicle-stimulating hormone decreased, both of which play crucial roles in reproductive health. In those following the ultra-processed food diet, researchers also discovered higher levels of a certain type of phthalate (pronounced tha-late) — a group of chemicals used in plastics known to disrupt endocrine function.

These findings underscore the idea that it’s not just what we eat, but how our food is processed that matters.