Watch your waistline: Fat men have bad sperm
BARCELONA, Spain (AP) - July 10, 2008 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."
But experts aren't sure if that necessarily means obese men face
major difficulties having children.
"If you have a man who isn't fantastically fertile with a
normal partner who is fertile, her fertility will compensate,"
said Dr. William Ledger, a professor of obstetrics and gynecology
at Britain's University of Sheffield, who was unconnected to the
study.
But if both partners are heavy, Ledger said that could be a
problem, since obesity is known to decrease women's fertility.
Shayeb and colleagues analyzed the sperm samples of more than
5,000 men in Scotland, and divided the men into groups according to
their Body Mass Index. Men who had an optimal BMI (20 to 25) had
higher levels of normal sperm than those who were overweight or
obese.
Fat men had a 60 percent higher chance of having a low volume of
semen, according to Shayeb's research. They also had a 40 percent
higher chance of having some sperm abnormalities.
Shayeb and colleagues found that underweight men were just as
likely to have the same problems as obese men. "But there were not
many underweight men in Scotland," he noted.
The researchers adjusted their analysis to account for other
factors that could have affected men's sperm count, like smoking,
alcohol intake, history of drug abuse, and age.
"Male fitness and health are clearly linked to a man's
fertility," said Neil McClure, professor of obstetrics and
gynecology at Queen's University in Belfast.
The study supported results of an earlier sperm study done by
doctors at hospitals and universities in Denmark.
There are several theories about why obese men might have bad
sperm. Because fat tissue influences the metabolism of sex
hormones, scientists think it might also disrupt sperm production.
It could also be a temperature problem. Sperm is best produced
at a temperature two degrees cooler than normal body temperature.
But because obese men have more fat, Shayeb said their bodies might
be overheated.
Another study presented at the conference concluded that
diabetes in men damages their sperm and is linked to male
infertility.
Con Mallidis and colleagues at Queen's University in Belfast
examined semen samples from nearly 40 men who were being treated
for diabetes, but were not overweight. They found significant DNA
damage linked to the excess sugar in the body from diabetes.
They found that diabetic men had twice the rate of DNA damage in
their sperm as men without diabetes.