BIGbad
10-23-2004, 11:03 PM
Size Matters... Sort of
A number of recent studies on human reproduction have been adding ammunition to the debate on whether or not size matters when it comes to sex.
As it turns out, size may matter for successful reproduction (i.e. getting the woman pregnant) but it is not the size of a man's penis that makes the difference - it is the size of his waistline. This may also apply to women, the Associated Press reports.
In one recent study of more than 1,500 young Danish men, it was discovered that those who are overweight - or underweight - are more likely to have poor sperm quality.
The study was conducted by doctors at various hospitals and universities in Denmark and published in the October issue of Fertility & Sterility, the reproductive society's journal. It involved 1,558 men with an average age of 19, who volunteered to give semen samples during mandatory exams for military service in two cities, Amsterdam and Aalborg.
Sperm counts, sperm concentration, semen volume and other measures of sperm quality such as shape and motility were measured, along with testicle size and hormone levels. Researchers also calculated each man's body mass index (BMI), a measure of obesity that takes into account height and weight.
Scores for men with healthy BMIs -- between 20 and 25, or 139 to 174 pounds for a man who is 5-foot-10 -- were compared to those of men above and below that range.
Sperm counts and sperm concentration were 28.1% and 36.4% lower, respectively, in underweight men. The same measures were 21.6% and 23.9% lower, respectively, in overweight men.
Women showed similar results in a separate study led by Dr. David Ryley of Beth Israel Deaconess Medical Center in Boston, Massachusetts.
"Among the severely obese, we saw significantly reduced implantation and pregnancy rates," said Dr. Ryley, who presented results of the women's study this week at a meeting of the American Society for Reproductive Medicine.
The study on women involved 5,847 attempts at in vitro fertilization (IVF) in which embryos are fertilized in a lab dish, at Beth Israel's infertility clinic, Boston IVF.
Obese women -- whose BMIs were 35 and over -- had little more than a 1 in 5, or about a 20%, chance of becoming pregnant through IVF; the odds were better than 25% for women with healthy weights. Embryos were also less likely to implant in the fat women.
Overweight women have irregular periods and lower ovulation rates, making it harder for them to get pregnant naturally, Ryley said. When given fertility treatments, they often need higher doses of drugs and for a longer time to spur ovulation, he said.
His study did not find that very thin women had more trouble conceiving as some previous research has suggested.
Why overweight men and women are less likely to reproduce is still not known, but there are plenty of physicians looking into the matter.
Regarding men, "It may be an alteration in hormonal values," said Dr. Anthony J. Thomas, Jr., a Cleveland Clinic urologist and president of the Society for Male Reproduction and Urology. Dr. Thomas was not involved in either the Danish or the Beth Israel studies.
Men produce and need a certain amount of the female hormone estrogen. Fat cells produce estrogen, so too much or too little of it may be a problem, Thomas said.
Other research suggests smoking and heavy alcohol use also harm sperm production. The Danish study is a reminder that doctors should always check a man for signs of infertility when couples are having trouble conceiving because the problem is just as likely to involve men as women.
"It's not uncommon for a man to come in after his wife has had a million tests" and then discover the problem is with his sperm, Thomas said. "It's probably one of the first things a doctor should do."
From the Voyeurweb!
A number of recent studies on human reproduction have been adding ammunition to the debate on whether or not size matters when it comes to sex.
As it turns out, size may matter for successful reproduction (i.e. getting the woman pregnant) but it is not the size of a man's penis that makes the difference - it is the size of his waistline. This may also apply to women, the Associated Press reports.
In one recent study of more than 1,500 young Danish men, it was discovered that those who are overweight - or underweight - are more likely to have poor sperm quality.
The study was conducted by doctors at various hospitals and universities in Denmark and published in the October issue of Fertility & Sterility, the reproductive society's journal. It involved 1,558 men with an average age of 19, who volunteered to give semen samples during mandatory exams for military service in two cities, Amsterdam and Aalborg.
Sperm counts, sperm concentration, semen volume and other measures of sperm quality such as shape and motility were measured, along with testicle size and hormone levels. Researchers also calculated each man's body mass index (BMI), a measure of obesity that takes into account height and weight.
Scores for men with healthy BMIs -- between 20 and 25, or 139 to 174 pounds for a man who is 5-foot-10 -- were compared to those of men above and below that range.
Sperm counts and sperm concentration were 28.1% and 36.4% lower, respectively, in underweight men. The same measures were 21.6% and 23.9% lower, respectively, in overweight men.
Women showed similar results in a separate study led by Dr. David Ryley of Beth Israel Deaconess Medical Center in Boston, Massachusetts.
"Among the severely obese, we saw significantly reduced implantation and pregnancy rates," said Dr. Ryley, who presented results of the women's study this week at a meeting of the American Society for Reproductive Medicine.
The study on women involved 5,847 attempts at in vitro fertilization (IVF) in which embryos are fertilized in a lab dish, at Beth Israel's infertility clinic, Boston IVF.
Obese women -- whose BMIs were 35 and over -- had little more than a 1 in 5, or about a 20%, chance of becoming pregnant through IVF; the odds were better than 25% for women with healthy weights. Embryos were also less likely to implant in the fat women.
Overweight women have irregular periods and lower ovulation rates, making it harder for them to get pregnant naturally, Ryley said. When given fertility treatments, they often need higher doses of drugs and for a longer time to spur ovulation, he said.
His study did not find that very thin women had more trouble conceiving as some previous research has suggested.
Why overweight men and women are less likely to reproduce is still not known, but there are plenty of physicians looking into the matter.
Regarding men, "It may be an alteration in hormonal values," said Dr. Anthony J. Thomas, Jr., a Cleveland Clinic urologist and president of the Society for Male Reproduction and Urology. Dr. Thomas was not involved in either the Danish or the Beth Israel studies.
Men produce and need a certain amount of the female hormone estrogen. Fat cells produce estrogen, so too much or too little of it may be a problem, Thomas said.
Other research suggests smoking and heavy alcohol use also harm sperm production. The Danish study is a reminder that doctors should always check a man for signs of infertility when couples are having trouble conceiving because the problem is just as likely to involve men as women.
"It's not uncommon for a man to come in after his wife has had a million tests" and then discover the problem is with his sperm, Thomas said. "It's probably one of the first things a doctor should do."
From the Voyeurweb!