According to a research conducted at the National Institute of Environmental Health Sciences (NIEHS) (one of the National Institutes of Health) men with increased body mass index (BMI) or obese are significantly more likely to be infertile that normal-weight men.

Lead author of the study, Markku Sallmen, stated that a 20-lb. increase in men's weight could increase the chances of being infertile by 10 percent.

BMI, a number calculated from a person's weight and height, provides a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems.

"Women who are overweight or obese tend to have a more difficult time becoming pregnant than normal-weight women, but whether men who are overweight or obese also have fertility problems had not been studied," says Donna Baird, Ph.D., an NIEHS epidemiologist with the study.

The said study results came from couples enrolled in the Agricultural Health Study (AHS) and is published in the September 2006 issue of Epidemiology.

Read the full report from NIH/NIEHS.