August 12, 2010

Obesity In Young Men Could Affect Sperm Count

Obesity in younger men may lead to lower sperm count, a new study reported in the journal Fertility and Sterility suggests.

The findings add to evidence that ties obesity to relatively poorer quality sperm.

Several recent studies have found that compared with thinner males, obese men tend to have lower sperm counts, fewer rapidly mobile sperm and fewer progressively motile sperm, which refers to sperm that swim forward in straight lines rather than swimming about aimlessly.

But age is also a puzzling factor in examining the relationship between obesity and sperm quality. Older men tend to have lower sperm quality than younger men and they also tend to have more body fat.

Among the more than 2,000 men in the new study, however, obese men between the ages of 20 and 30 generally had a lower sperm count than normal-weight men in the same age group.

Studies have so far come to conflicting results as to whether obesity actually impairs a man's fertility, and the latest findings do not reveal whether the difference in sperm count between obese and thin males would be enough to also make a difference in their fertility, according to lead researcher Dr. Uwe Paasch, of the University of Leipzig in Germany.

Paasch and colleagues used information from a database of men who had come to fertility clinics for a semen analysis between 1999 and 2005. More than 2,150 men averaging 30 years old, and having no infertility problems, were included in the study.

Obese men had a relatively lower sperm count then thinner men, but were still within the normal range. The normal range is considered to be between 20 and 150 million per millimeter of semen, according to the National Institute of Health (NIH).

"We do not know in detail" whether the difference in sperm count between obesity and normal-weight men would affect their fertility. But, the relationship between weight and sperm count offers young men another reason to try to maintain a normal, healthy weight, Paasch told Reuters Health in an email.

It is not fully clear why obesity is related to sperm quality. Some studies have found that obese men tend to have altered testosterone levels and other reproductive hormones compared to thinner men. In this study, though, hormone levels correlated with age, but not with body weight.

The new study had a number of limitations, including the fact that men were patients at a fertility clinic rather than a sample from the general population.

The researchers also point out that weight categories were based on body mass index, or BMI, a measure of weight in relation to height. The problem is that BMI does not precisely reflect a person's level of body fat.

Other studies have suggested that body fat, and abdominal fat in particular, is more closely related to sex-hormone levels than is BMI.


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