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Obesity may affect sex hormone levels but not sperm count

6 October 2008
Appeared in BioNews 478

A study of 2000 men, conducted by Dr Anette Aggerholm and colleagues at Aarhus University Hospital in Denmark, has found no association between obesity and semen quality. The study, published in the journal Fertility and Sterility, involved taking blood and semen samples from all participants as well as recording lifestyle information, height and weight. In contrast, other recent studies (summarised in a literature review this month in Fertility and Sterility) have linked obesity with decreased fertility.

The men who took part in the study ranged in age from 18 to 66 years old and nearly half were overweight. The researchers noted that levels of hormones were generally more decreased the more overweight a man was, and men who were moderately overweight had slightly lower sperm counts than men of average weight. However, obese men did not have lower sperm counts or sperm quality than men of an average weight. Dr Aggerholm concluded that, whilst there was a strong association between obesity and hormonal changes, there was no such association between obesity and semen quality.

Work published in the same journal in August this year by Dr Eric Pauli and his colleagues at Pennsylvania State University College of Medicine, US, also found that obese men had lower levels of sex hormones in their blood. The much smaller study of only 87 men found that the more obese a man was, the lower his levels of hormones essential for reproduction. Dr Pauli and colleagues did not assess semen quality but suggest that hormonal changes could act to decrease a man's fertility when acting in concert with dampened libido and increased risk of erectile dysfunction (both of which have been established by previous studies of obesity).

A literature review published this month, also in Fertility and Sterility and authored by Dr Hammoud and colleagues of University of Utah School of Medicine, US, concludes that there is now good evidence for a link between obesity and decreased fertility in males. They call for greater clinician awareness of the effects of obesity on fertility as well as studies into the reversibility of obesity-associated male infertility with weight loss.

Obesity may diminish a man's fertility
Reuters |  19 September 2008
Obesity not linked to poor semen quality
Reuters |  1 October 2008
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