Overweight and obese men in a new study
showed diminished quantity and quality of semen, suggesting that a weight
problem might also affect fertility, researchers say.
"The heavier the men, the higher the
chances of a low sperm count," urologist Dr Keith Jarvi told Reuters
Health. "I don't think that this message is well known or appreciated by
men in general," said Jarvi, who was not involved in the new study.
Dr Michael Eisenberg, of Stanford
University School of Medicine in California, and his colleagues recruited 468
couples in Texas and Michigan who were planning to conceive a child and tested
several aspects of the men's semen.
Lower ejaculate volume
They also weighed the men and measured
their waists and found that greater waist circumference and body mass index
(BMI) – a measure of weight relative to height – were both linked to lower
ejaculate volume. "All aspects of semen quality are important,"
"Ejaculate has several chemicals that
provide a safer environment for sperm. As such, if the volume is low it may be
Sperm count, another important
metric, was lower among men with bigger waists. "The sperm count is just
that: the number of sperm in each cc of semen," said Jarvi, director of
the Murray Koffler Urologic Wellness Centre and Head of Urology at Mount Sinai
Hospital in Toronto, Canada.
Higher semen volume, within the optimal
range between 2 and 5 millilitres, will overall have more sperm, Jarvi said. A
volume under 1.5 mls may cause infertility, he said, but too much is not good
Results of the study
In the study, a typical man in the normal
BMI range had an ejaculate volume of 3.3 ml, compared to 2.8 ml for men in the
highest BMI category, severely obese.
Men with the largest waists, over 40
inches, had about 22 percent lower total sperm count compared to men with waist
measurements under 37 inches.
There appeared to be no link to semen
concentration, motility, vitality or physical appearance, according to the
results published in the journal Human Reproduction.
About half of the men had already fathered
children when the study took place and none of the couples were seeking help
with infertility when they were recruited.
The researchers also did not follow up to
see whether the men succeeded in having children later.
Most men exercised less than once per week,
so the authors couldn't really examine what effects more exercise might have on
sperm. "The big question is what does reduction in body weight do to the
sperm counts in men starting with a low sperm count?" Jarvi said.
"This is the question that my overweight patients ask."