Researchers at the University of Aberdeen in the UK found that obese men have a higher proportion of abnormal sperm and a lower volumes of seminal fluid, which can make it harder to conceive.
By contrast men who had an optimal body mass index had higher levels of both normal sperm and semen volumes than other groups.
Dr. A Ghiyath Shayeb, who led the study, noted that he suspected there would be a link between weight and fertility in men, as this connection already exists in women.
"Our findings were quite independent of any other factors," he said, "and seem to suggest that men who are trying for a baby with their partners, should first try to achieve an ideal body weight."
He added that adopting a healthy lifestyle, exercising regularly and eating a balanced diet will in "the vast majority of cases" allow would-be dads to reach a normal body mass index.
In related news, researchers as the Eylau Centre for Assisted Reproduction in Paris recently found that men’s fertility levels begin to drop when they reach 40.