Spain ? Too many fatty foods are dangerous not only to men’s waistlines, but also to their sperm production.

In research presented Wednesday at a meeting of the European Society of Human Reproduction and Embryology, scientists found that obese men have worse sperm than normal-weight men.

“There is a very long list of health hazards from being overweight,” said Ghiyath Shayeb, the study’s lead researcher at the University of Aberdeen. “Now we can add poor semen quality to the list.”

Experts aren’t sure that necessarily means obese men face major difficulties having children. But if both partners are heavy, that could be a problem because obesity is known to decrease women’s fertility.