Researchers from the University of Aberdeen found that men of average weight have healthier sperm in higher volumes than those outside the normal range. The research follows reports made by doctors earlier this week that male fertility begins to decline when men reach their mid-30s.
University of Aberdeen researchers looked at the sperm of more than 2,000 men in couples having problems conceiving. A closer examination revealed DNA damage of sperm in the heaviest men as well as those who had diabetes. Too much fat around the male testicles causes sperm to heat up, scientists have suggested.
The quality of sperm DNA is linked to decreased embryo quality, low embryo implantation rates, higher miscarriage rates and some serious childhood diseases, including cancers.
Additionally, the study found that being underweight can also cause problems with sperm. Men with a higher body mass index (BMI, a ratio of weight to height) had less seminal fluid and more abnormal sperm.
The findings showed that men with an optimal BMI of 20 to 25 had higher levels of normal sperm and high semen volume than those who were either overweight or underweight. Previous research has shown that obesity affects women's chances of getting pregnant.
