Obesity in Men Linked to Infertility
Men with increased body mass index, or BMI, were significantly more likely to be infertile than normal-weight men, according to a report in the journal Epidemiology.
Study lead author Markku Sallmen, Ph.D., at the Finnish Institute of Occupational Health, says the researchers found that a 20-pound increase in a man's weight may increase the chance of infertility by about 10 percent.
BMI is a measure of weight proportionate to height. BMI is considered a useful measurement of the amount of body fat. Occasionally, some very muscular people may have a BMI in the overweight range.
However, these persons are not considered overweight because muscle tissue weighs more than fat tissue. Generally, BMI can be considered an effective way to evaluate whether a person is overweight or obese.
According to the National Heart, Lung, and Blood Institute (NHLBI), a BMI from 18.5 to 24.9 is considered normal while a BMI of more than 25 is considered overweight.
A person is considered obese if the BMI is greater than 30 and morbidly obese if the BMI is 40 or greater. In general, after the age of 50, a man’s weight stabilizes and even drops slightly between the ages of 60 and 74. However, a woman’s weight continues to increase until age 60 and then begins to drop.
The researchers studied couples enrolled in the Agricultural Health Study (AHS), a large project that began in 1993 examining factors that impact the health of farmers and their families in agricultural communities.
The research was conducted at the National Institute of Environmental Health Sciences (NIEHS), one of the National Institutes of Health.
"Women who are overweight or obese tend to have a more difficult time becoming pregnant than normal-weight women, but whether men who are overweight or obese also have fertility problems had not been studied," says researcher Donna Baird, Ph.D., at the NIEHS.
The data on infertility and body mass came from questionnaires that 1,468 farmers and their wives completed when they enrolled in the study.
The wives completed a family health questionnaire, which included information about the couple's reproductive history. The men reported their weight and height on a questionnaire about their health.
The analysis was limited to couples with a pregnancy attempt during the four years before enrollment, and to women under the age of 40.
The researchers divided the couples into infertile and fertile groups. The infertile couples were those that tried for longer than a year to conceive, and the fertile couples were those that conceived within a year.
The majority of men and women were more than 30 years old. Twenty-eight percent of the couples had experienced infertility.
Researchers found that men's BMI was an “independent risk factor” for infertility.
The researchers adjusted for other factors that could affect fertility, including high BMI of the woman, age, cigarette smoking, alcohol intake, and solvent and pesticide exposure. After this, there was a general increase in infertility with increased BMI, reaching a nearly two-fold increase among obese men.
When researchers divided the sample into two equal groups by men's age, they found that men's BMI was a risk factor for infertility in both the older and younger men.
The researchers did not have data on frequency of sexual intercourse, so it is possible that overweight men have less sexual intercourse than their normal weight counterparts and this could influence fertility.
However, there have been recent studies looking at semen characteristics that show lower semen quality for overweight and obese men, as well as hormonal differences.
"This study provides data on some additional health problems associated with obesity," says Dr. David A. Schwartz, director of the NIEHS. "Preventing obesity can help improve men's overall health, perhaps even their reproductive health."
Always consult your physician for more information.
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Infertility is defined by the American Society for Reproductive Medicine (ASRM) as a disease of the reproductive system that impairs the body's ability to perform the basic function of reproduction.
Although conceiving a child may seem to be simple and natural, the physiological process is quite complicated and depends on the proper function of many factors, including the following, as listed by the ASRM:
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production of healthy sperm by the man
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production of healthy eggs by the woman
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unblocked fallopian tubes that allow the sperm to reach the egg
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the sperm's ability to fertilize the egg
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the ability of the fertilized egg to become implanted in the uterus
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adequate embryo quality
The average chance to conceive for a normally fertile couple having regular, unprotected intercourse is approximately 25 percent during each menstrual cycle. In most couples, conception occurs within about 12 months. However, infertility affects about 12 percent of couples of childbearing age.
Infertility is not just a woman's concern. A problem with the male is the sole cause, or a contributing cause, of infertility in about 40 percent of infertile couples. About one-third of infertile couples have more than one cause or factor related to their inability to conceive. About 20 percent of couples have no identifiable cause for their infertility after medical investigation.
The following is a list of risk factors related to male infertility (also called male factor or male factor infertility):
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history of prostatitis or genital infection
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testicular trauma or torsion
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history of precocious puberty (puberty occurring at a young age) or delayed puberty (puberty occurring at an older age)
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exposure to toxic substances or hazards on the job, such as lead, cadmium, mercury, ethylene oxide, vinyl chloride, radioactivity, and x-rays
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cigarette or marijuana smoke
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heavy alcohol consumption
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exposure of the genitals to high temperatures
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hernia repair
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undescended testicles
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prescription drugs for ulcers or psoriasis
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DES taken by mother during pregnancy
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mumps after puberty
Problems with the production and maturation of sperm are the most common causes of male infertility. Sperm may be immature, abnormally shaped, or unable to move properly. Or, normal sperm may be produced in abnormally low numbers (oligospermia) or seemingly not at all (azoospermia).
Other conditions and/or anatomical abnormalities may also be associated with male infertility.
Always consult your physician for more information.
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