Being overweight does not decrease the production of sperm, states a new study.
Nanette Santoro, MD, an Albert Einstein College of Medicine obstetrician-gynaecologist trained in reproductive endocrinology, said that the findings of the study, performed in New York in nearly 300 very overweight men, were unexpected.
"We see pretty significant deficits in fertility in women due to obesity, so we thought we'd see an effect in men. But that wasn't the case," Santoro said.
For the study, Santoro and her colleagues examined 292 men who gave semen samples at fertility clinics.
The men were ages 18 to 50 and, on average, had a body mass index (BMI) of 28, which is considered nearly obese.
The researchers found that greater body weight was not associated with worse sperm production or sperm motility.
According to Santoro, impaired sperm production is the cause of infertility in 90 percent of infertile men. She said that about 6 percent of reproductive-age men are infertile.
Increasing body weight was linked to lower testosterone in the 31 study participants for whom testosterone was tested.
However, Santoro said low testosterone causes infertility only if it is very low or occurs in morbidly obese men.
"Our results show that the process of making sperm is pretty robust and is hard to interrupt. It's good news for men that body size may be less related to fertility than it is in women," Santoro said.
She warned that the findings should not serve as an excuse for overweight men to avoid losing weight.
The results will be presented at The Endocrine Society's 90th Annual Meeting in San Francisco.