Male Weight and Fertility
August 2014
Volume 5, Issue 3

Bariatric Surgery Improves Hormone Levels and Erectile Function, and Does Not Alter Sperm Quality

Reprod Sci. 2012;19(10):1057-1062

Introduction: Previous studies have demonstrated that obesity can negatively impact sexual function, hormone levels, and other measures of fertility in men. This study was designed to investigate whether weight loss either by diet and exercise or by bariatric surgery altered sexual function, hormone levels, or sperm quality.

Methods: Twenty men who were morbidly obese (>40 kg/m2) were randomized to an intensive supervised lifestyle intervention program for weight loss (exercise and diet) for 4 months followed by gastric bypass surgery (n=10) or to a control group that received education on healthy food and exercise but no specific intervention (n=10) for 24 months. Blood samples were taken to analyze hormone levels, semen samples were used to assess sperm quality, and all participants completed the International Index of Erectile Function (IIEF-5) questionnaire.

Results: At four months, the group that received the lifestyle intervention showed a significant decrease in BMI compared to the control group (-12.6 kg/m2 vs -2.1 kg/m2; P=0.0033); however, no changes were found in hormone levels, erectile function, or sperm quality.

At 20 months after bariatric surgery, the men in the intervention group showed reduced BMI by 24.7 kg/m2 (P<.0001) compared with a non-significant BMI decrease of 0.7 kg/m2 in the control group. There was a significant increase in IIEF-5 score, total testosterone, and follicle-stimulating hormone (FSH) level (P = 0.0469, 0.0349, and 0.0025), and decrease in prolactin level (P<.0001) at 20 months compared with baseline levels.  The intervention group also showed significant improvements in IIEF-5 score and free and total testosterone levels as compared with the control group at 20 months (P = 0.0224, 0.0149, and 0.0043, respectively).

In contrast, sperm profiles did not significantly change from baseline levels in the bariatric surgery group at any time point and there were no between-group differences.

Conclusion: Bariatric surgery does not improve sperm quality in morbidly obese men, but does improve sexual function and hormone parameters.


Tamara L. Wexler, MD, PhD, is an endocrinologist specializing in reproductive and neuroendocrinology, and an Attending in Medicine, Massachusetts General Hospital, Boston, MA.

This study looked at a small cohort of morbidly obese men (n=20, mean BMI 54-55.7 kg/m2). Men in the intervention arm were on average 5.5 years younger than men in the control group, though given the small sample size this did not reach significance. Intervention consisted of targeted health education for 4 months followed by bariatric surgery. The control group received general education for the 4-month period; given the extreme BMI of the control group, one would not expect health education alone to have an impact in the control group.

Outcome measures included serum hormones (total and free testosterone, estradiol, prolactin, luteinizing hormone, and FSH; sex hormone-binding globulin, and inhibin-B were not measured), semen analysis (sperm concentration, progressive motility, and morphology), and erectile function (measured by the IIEF-5 questionnaire). At each time point, only one morning blood draw was performed. Baseline outcome measures were not significantly different between the intervention and control groups.

Four months of targeted lifestyle intervention yielded a mean BMI reduction of 12.6 kg/m2, but no changes in serum hormones or semen analysis in either group. Twenty months after bariatric surgery, the intervention group had a mean BMI reduction of 24.7 kg/m2 (total, including the initial loss); the group had increased testosterone and FSH, decreased prolactin, and increased IIEF-5 score. However, no changes were seen in the semen analysis, neither between time points in the intervention group nor between intervention and control group. That is, the group that did experience weight loss was found to have serum hormone changes but not alterations in sperm quality measurements, whether after lifestyle intervention or bariatric surgery.

While this study had limitations—including the small size and focus on morbidly obese men (mean BMI 54-55.7 kg/m2)—which limit generalizability, the change in serum hormones but not semen parameters is interesting, and in part echoes some of the findings of the study by Chavarro and colleagues. Larger studies, with additional measures, will add further information to the impact of bariatric surgery on measures of reproductive potential.

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