| |
Being either too thin or too heavy may lower
a man's sperm count, in some cases enough to impair fertility,
researchers report. In a study of nearly 1,600 young Danish
men, the investigators found that those with either a low or
high body mass index (BMI) had differences in reproductive
hormones, as well as lower sperm counts than normal-weight
men.
|
| |
NEW YORK (Reuters Health), Oct 29, 2004
In some cases, these weight-related
effects would likely be enough to reduce a man's fertility,
study leader Dr. Tina Kold
Jensen, of the University of Southern Denmark, told Reuters
Health.
For example, men with a high or low BMI were more likely
than normal-weight men to have a sperm count below 20 million
per milliliter of semen, which is abnormally low.
The findings
raise the possibility that the high prevalence of obesity in
the Western world may be contributing to fertility problems,
Jensen and her colleagues report in the journal Fertility & Sterility.
If that's the case, they note, it would mean that some cases
of impaired fertility may be preventable.
However, Jensen said,
it's not yet known whether maintaining a normal weight can
help a man's chances of fathering children. To answer that
question, she added, researchers could study whether overweight
men who shed their excess pounds show changes in semen quality.
Body weight has already been shown to affect a woman's ability
to conceive. Obese women, for example, have a heightened risk
of menstrual irregularities and infertility To see whether
BMI -- a measure of weight in relation to height -- may be
related to male fertility, Jensen's team studied young men
who were undergoing physicals for potential military service.
They found that, on average, those with a low BMI -- defined
as below 20 -- had a 36 percent lower sperm count than men
with a normal BMI. Overweight men -- those with a BMI over
25 -- had a 24 percent lower sperm count compared with average-weight
men.
In addition, the men's testosterone levels decreased as
BMI increased, as did certain other reproductive hormones.
According to Jensen's team, it may be such hormonal effects
of a high BMI that explain the poorer semen quality they found
in overweight men.
As for the underweight men, malnutrition
or "subclinical" health problems may take some of the blame
for their lesser semen quality, the researchers speculate.
They add, though, that hormonal imbalances could have been
at work in these men as well.
It's also possible, according
to Jensen, that the types of lifestyles that promote extremes
in weight may explain the link between BMI and semen quality.
Men in the study were asked about their smoking and drinking
habits, but factors such as lack of exercise and poor diet
may also be important, Jensen noted.
SOURCE: Fertility & Sterility, October 2004.
© Copyright
Reuters 2004
|
Infertility