Obese men are more than three times as likely to have low sperm counts compared with the normal-weight ones ,according to a study in the Fertility and Sterility quoted by media reports Wednesday.

The heaviest men are also at triple a risk of having a low count of progressively motile sperm, found the study by Dr. Ahmad O. Hammoud of the University of Utah in Salt Lake City and colleagues.

"There is a strong relationship between overweight and obesity and altered sperm parameters," according to Hammoud and his team.

Obesity may impair fertility in men, the researchers note, while increased body fat can contribute to lower testosterone levels and higher estrogen levels. To examine how body mass index (BMI) affects sperm quality, they evaluated 390 men who sought infertility treatment with their partners over a two year period.

24 percent of the men were normal weight, while 43 percent were overweight, and 33 percent were obese. Overall, 10.5 percent had low sperm counts.

The prevalence of low sperm counts rose as BMI increased; obese men were 3.3 times more likely to have low sperm counts than normal-weight men. The risk of having a low count of progressively mobile sperm also rose with BMI; obese men were 3.4 times more likely than normal-weight men to have a low progressively mobile sperm count. Obese men were also 1.6 times more likely than overweight or normal-weight men to have a high percentage of abnormally shaped sperm.

The fact makes it likely that the study group had worse sperm quality than the population at large, Hammoud and colleagues point out.

(Agencies via Xinhua December 31, 2008)