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Study Finds Overweight Men Have Lower Sperm Counts

Posted on: Friday, 11 July 2008, 00:20 CDT

Obese men should consider losing weight if they want to have children, according to new research presented at a meeting of the European Society of Human Reproduction and Embryology.

Dr. A Ghiyath Shayeb, from the University of Aberdeen, Aberdeen, UK, said his research found that men with a higher body mass index (BMI) had lower volumes of seminal fluid and a higher proportion of abnormal sperm.

"There is a very long list of health hazards from being overweight," said Dr Shayeb, the study's lead researcher at the University of Aberdeen.

"Now we can add poor semen quality to the list."

"We felt that it was possible that male overweight might contribute to fertility problems…..particularly since it is a known risk factor for problems in conceiving among women," he said.

Dr. Shayeb and colleagues examined seminal fluid analysis of 5316 men attending Aberdeen Fertility Center for conception difficulties. Of these, 2037 had complete data on their BMIs.

The scientists divided the men into four groups according to their BMI.  After accounting for characteristics that could confound the analysis, such as alcohol consumption, smoking, age, social deprivation and the length of time of abstinence prior to producing the sample, the team looked for a relationship between semen quality and BMI.

They discovered that men with an optimal BMI of 20-25 had higher levels of normal sperm than those in the other groups.  Additionally, they had higher semen volume.  

The overweight men, on the other hand, had a 60 percent higher chance of having a low volume of semen, according to the research. They also had a 40 percent higher chance of having some sperm abnormalities.

"The mechanism for the relationship could be a number of things – different hormone levels in obese men, simple overheating of the testicles caused by excessive fat in the area, or that the lifestyle and diet that leads to obesity could also lead to poorer semen quality. We just don't know the answer yet, but this is an important question that needs urgent attention."

Interestingly, the research 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," Dr. Shayeb noted.

The team observed no significant difference between the four BMI groups in sperm motility or concentration.

The researchers did not examine DNA damage in the sperm, but instead reviewed the parameters of the routine semen analysis.

"Other studies have suggested an association between male obesity and increased DNA damage in the sperm, which can be associated with reduced fertility as well," said Dr. Shayeb.

"Our findings were quite independent of any other factors….and seem to suggest that men who are trying for a baby with their partners, should first try to achieve an ideal body weight. This is in addition to the benefit of a healthy BMI for their general well being.

"Adopting a healthy lifestyle, a balanced diet, and regular exercise will, in the vast majority of cases, lead to a normal BMI. We are pleased to be able to add improved semen quality to the long list of benefits that we know are the result of an optimal body weight."

But experts aren't sure if the research necessarily means overweight and obese men face major obstacles conceiving.

"If you have a man who isn't fantastically fertile with a normal partner who is fertile, her fertility will compensate," Dr. William Ledger, a professor of obstetrics and gynecology at Britain's University of Sheffield, who was not involved in the research, told the Associated Press.

But Ledger said if both partners are overweight it could be a problem, since obesity is known to decrease women's fertility.

Dr. Shayeb’s team intends to expand their research by comparing male BMI in fertile and infertile couples to determine if poorer semen quality correlates with reduced fertility.

"There has been a significant rise in the numbers of men with poorer semen parameters in the industrialized world," said Dr. Shayeb.

"But this has not been reflected so far in male infertility. To compare male BMI in these two groups therefore seemed to us to be a logical next step."

Dr. Shayeb said additional research is also needed on obesity’s impact on semen production.

Source: redOrbit staff and wire reports

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