High body mass index has a deleterious effect on semen parameters except morphology Results from a large cohort study

In this large cohort study of 10,665 men, semen quality, including volume, sperm concentration, and progressive motility, decreased with increased body mass index. Morphology was unaffected.

Stéphanie Belloc, Pharm.D., Martine Cohen Bacrie, M.D., Edouard Amar, M.D., Vincent Izard, M.D., Moncef Ben Khalifa, Ph.D., Alain Dalleac, M.D., Jacques de Mouzon, M.D., M.P.H.

Volume 102, Issue 5, Pages 1268-1273


To evaluate the influence of body mass index (BMI) on semen characteristics.

Cohort study.

Single private andrology laboratory.

All patients (n = 10,665) consulting for a semen analysis from October 9, 2010, to October 8, 2011. When analyses were repeated on the same patient, only the first was included.

Recording of self-reported weight and height and of semen analysis.

Main Outcome Measure(s):
All parameters of standard semen analysis: pH, volume, sperm concentration per mL, total sperm count per ejaculate, motility (%) within 1 hour after ejaculation (overall and progressive), viability (%), and normal sperm morphology (%). Parametric and nonparametric statistical methods were applied, and results are given either with mean ± SD, or 10th, 50th, and 90th percentiles.

Semen volume decreased from 3.3 ± 1.6 to 2.7 ± 1.6 mL when BMI increased from normal (20–25 kg/m2) to extreme obesity (>40 kg/m2). The same was true for semen concentration (56.4 ± 54.9 to 39.4 ± 51.0 million/mL), total sperm count (171 ± 170 to 92 ± 95 million), and progressive motility (36.9 ± 16.8% to 34.7 ± 17.1%). The percentage of cases with azoospermia and cryptozoospermia increased from 1.9% to 9.1% and from 4.7% to 15.2%, respectively. The other semen characteristics were not affected. Multivariate models including age and abstinence duration confirmed these results.

In this study, on a large patient sample size, increased BMI was associated with decreased semen quality, affecting volume, concentration, and motility. The percentage of normal forms was not decreased.

  • This is a very large retrospective review from a single andrology lab studying the impact of BMI on semen parameters with >10,000 infertile subjects – one of the largest studies to date. The findings demonstrate the impact of obesity on semen analysis and subsequently fertility status. As BMI increased, there was a statistically significant decline in volume, concentration, count, viability, and progressive motility. Interestingly, morphology was not different.

    There were no comments on medical conditions of the subjects (ie hypogonadism, varicocele, diabetes, hypothyroid/hyperthyroid, medications taken, etc.)

    It would be interesting to see if the BMI effects on semen analysis would be the same for fertile men divided into respective BMI categories in this study.

    • Jason Kovac

      agree. would also be interested in seeing whether reduction of BMI has a similar effect on semen parameters. The other issue is that these are people presenting to an andrology laboratory… what about the general population?

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