Welcome from Tamara L. Wexler, MD, PhD
We previously examined the relationship between female weight—both underweight and overweight—and fertility (EndoScan, May 2014). We now turn our attention to male weight and fertility, and research investigating an association between male weight/adiposity and sexual function,1,2 serum hormone levels, and sperm parameters.
Initial evidence suggesting an association between male weight and infertility came from epidemiologic studies connecting higher male body mass index (BMI) to longer times to conception.3 Much of this data was based on surveys of the female partners. Recent studies have measured men’s serum hormone levels and/or semen parameters, without looking at time to conception or other more direct measures of fertility.
While the majority of studies suggest that increased weight is linked to poorer hormone or semen profiles,4-10 the data is not entirely consistent. For example, one analysis of pooled data from 5 population studies in Denmark (spanning 1992-2004) looking at environmental or occupational effects on semen found that obesity was statistically significantly associated with an altered hormone profile (lower testosterone and inhibin B and higher estradiol), but not with lower sperm count; overweight (but not obesity) was associated with reduced semen quality.11 A meta-analysis by MacDonald and colleagues published in 2010 concluded that BMI was not associated with decreased sperm concentration or count; the review included 31 studies published through February 2009, and the meta-analysis aggregated data from 5 studies.12
In the past several years, new research has expanded the understanding of the relationship between male weight and measures of fertility. We review 5 papers in detail in this EndoScan. A summary of the cohorts and outcome measures is presented in Table I.
Table I. Summary of Reviewed Studies
As with all studies, it is important to look at the cohort being studied. In the group included in this EndoScan, one study looked at a general population (Eisenberg et al),4 two looked at populations that had experienced difficulty with fertility (Hammiche et al and Chavarro et al),6,9 a meta-analysis included data from both populations (Sermondade et al),5 and one study looked at a morbidly obese group, some of whom underwent bariatric surgery (Reis et al).13
Sermondade and colleagues conducted a meta-analysis of BMI and semen parameters that included aggregated individual data from 21 studies.5 When sperm parameters were dichotomized, a J-shaped relationship was found between BMI groups and both sperm count and concentration. (Differences in methodology, outlined in the review and commentary, may account for the difference in results between this meta-analysis and that by MacDonald and colleagues.)12 This study also lends some insight into a potential impact of underweight on sperm. While the individual studies included in this EndoScan focus on overweight and obesity (as do most studies on male fertility), a number of the studies included in the Sermondade meta-analysis do include men with BMI <18.5 kg/m2, with an increased risk of abnormal sperm concentration seen in that group.
Chavarro and colleagues looked at serum hormone levels and semen parameters including sperm count and DNA damage, noting that increased sperm DNA damage was associated with obesity alone (after controlling for confounders), and not with the observed differences in serum hormones.9 In addition, they found a significantly lower sperm count only in men with severe obesity (BMI >35 kg/m2). They concluded that the hormonal changes (lower testosterone, higher estradiol) found with higher BMI are not associated with abnormal semen parameters. Hammiche and colleagues, also working with a population seeking fertility treatment, found that overweight (BMI 25-29.9 kg/m2) and obesity (BMI >30 kg/m2) were significantly associated with lower ejaculate volume and total sperm count; they did not, however, further subdivide the obese population to look at those with BMI >35 kg/m2.6 Eisenberg and colleagues, investigating similar parameters but in a general (not subfertile) population, found a trend towards lower ejaculate volume and total sperm count in both obese class I (BMI 30-34.9 kg/m2) and class II subjects (BMI >35 kg/m2), but the odds ratios for low volume and count (dichotomized values) reached significance in only the most obese group (BMI >35 kg/m2).4 They also looked at waist circumference (WC), and found that high-risk WC carried a significantly higher odds ratio for low sperm concentration and total count.
Does Weight Loss Improve Sperm Parameters?
Few studies have looked at the impact of lifestyle-related weight loss in a randomized controlled fashion. In the study by Reis and colleagues, an intervention group of 10 morbidly obese men (mean BMI 54-55.7 kg/m2) underwent four months of targeted lifestyle education prior to bariatric surgery, with monitoring of hormone levels, semen parameters, and (by questionnaire) erectile function.13 The intervention group had a 12.6 kg/m2 decrease in BMI after these four months, but without any resultant changes in hormone levels, erectile function, or sperm quality. Hakonsen and colleagues followed 43 men (20-59 years, BMI 33-61 kg/m2) through a 14-week residential weight-loss program.14 Weight loss was associated with improved serum testosterone, sex hormone-binding globulin (SHBG), and Anti-Müllerian Hormone values, and improved ejaculate volume and sperm count, particularly in those with largest degree of weight loss; the authors noted that the improvements seen with weight loss may have been due to the attendant lifestyle, diet, and exercise changes.
Reis and colleagues focused on a morbidly obese population, as the study was designed to also investigate the effect of bariatric surgery. At 20 months after bariatric surgery, with a reduction in BMI of 24.7 kg/m2 (from baseline), improvements were seen in hormone levels and erectile function but not in semen parameters. Facchiano and colleagues noted a similar improvement in serum hormones after bariatric surgery in a group of 20 obese men (median BMI 43.6 kg/m2), particularly evident in the younger subjects.15 The absence of change in semen parameters is in contrast to a worsening noted in 3 patients by Sermondade and colleagues: 1) a 30-year-old man with baseline BMI 65.7 kg/m2 who experienced reduced sperm concentration and motility at 10 and 13 months post-operation; 2) a 41-year-old man, baseline BMI 53.5 kg/m2, with worsening of already poor semen parameters at 6-months post-operation; and 3) a 30-year-old man, baseline BMI 38.6 kg/m2, with mild worsening of his already poor semen quality at 3 and 6 months post-operation.)16 The study of reproductive measures in this population is hampered by the variability of a small number of patients.
A study of the impact of weight loss on reproductive parameters but in a larger group of overweight and obese men (not only those with BMI >40 kg/m2) would provide further and more generalizable information.
Studies to date have employed a number of markers for reproductive health, including serum hormones, semen parameters, and quality of sperm (motility, DNA).
While results are not completely consistent across studies, and the interplay between weight/adiposity and serum hormones, semen parameters, and sperm quality is not clear, data generally suggests that increasing weight is associated with poorer reproductive measures. The associations identified do not necessarily represent a causal relationship, and, of note, none of the studies have looked at more direct measures of fertility, such as pregnancy.
Points for Patient Care
- Excess weight and adiposity in men is linked to altered reproductive hormones. (However, in obese individuals, a lower testosterone level does not indicate that supplementation is warranted; more information on testosterone supplementation can be found in the March 2014 EndoScan.)
- Excess weight is associated with altered semen parameters including sperm count and motility.
- Men seeking fertility may benefit from weight loss for reproductive as well as other health benefits. Weight loss from lifestyle modification has been shown to be helpful in a small number of studies; the impact of weight loss from bariatric surgery is less clear.
- Studies to date have focused on hormone and semen parameters, with a handful looking at time to conception. Studies investigating the impact of male weight on pregnancy or birth rates have yet to be conducted.
A Note on Measurements of Weight and Fat Distribution
In the studies reviewed here, weight and central adiposity are measured by BMI and WC, both have been shown to be independently associated with measures of fertility in women. BMI is used to measure weight, accounting for height.
The World Health Organization categorizes BMI as: underweight ≤18.5 kg/m2; normal weight 18.5-24.9 kg/m2; overweight 25-29.9 kg/m2; obese 30-39.9 kg/m2; morbidly obese ≥40 kg/m2.
Alternately, obesity is sometimes broken down into classes: class I obesity 30-34.99 kg/m2; class II 35-39.99 kg/m2; class III ≥40 kg/m2.
Waist circumference is used as a measure of central adiposity/fat distribution; according to the National Heart, Lung, and Blood Institute (NHLBI), the risk of heart disease and type 2 diabetes is higher for men with a WC >40 inches (101.6 cm).17 Some studies used both measures; once BMI is greater than 35 kg/m2, the NHLBI does not feel that WC measurements add to risk stratification.
Interpreting Measures of Fertility
Male reproductive hormones include testosterone, SHBG, estradiol, luteinizing hormone, follicle-stimulating hormone, and inhibin B. Study results have consistently found that higher BMI is associated with lower testosterone and SHBG and higher estradiol level. Indeed, fat cells synthesize the enzyme aromatase, and thus more conversion of testosterone to estradiol may be expected in individuals with more adiposity
The papers reviewed in this EndoScan refer to a number of semen parameters, including ejaculate volume, total sperm count, and sperm concentration. Of note:
Total sperm count = ejaculate volume × sperm concentration
Sperm quality may be more relevant than the number of sperm; measures of quality include motility, morphology, and DNA fragmentation. Sperm motility is graded as A to D, with types C and D considered of poor quality.18 (Grade A “fast progressive” sperm move forward quickly along a straight path; grade B “slow progressive” sperm move forward slowly or do not follow a straight path; grade C “nonprogressive” sperm move their tails but do not move forward; grade D “immotile” sperm do not move.)
1. Bacon CG, Mittleman MA, Kawachi I, et al. A prospective study of risk factors for erectile dysfunction. J Urol. 2006;176(1):217-221.
2. Esposito K, Giugliano F, Di Palo C, et al. Effect of lifestyle changes on erectile dysfunction in obese men: a randomized controlled trial. JAMA. 2004;291(24):2978-2984.
3. Sallmen M, Sandler DP, Hoppin JA, Blair A, Baird DD. Reduced fertility among overweight and obese men. Epidemiology. 2006;17(5):520-523.
4. Eisenberg ML, Kim S, Chen Z, et al. The relationship between male BMI and waist circumference on semen quality: data from the LIFE study. Hum Reprod. 2014;29(2):193-200.
5. Sermondade N, Faure C, Fezeu L, et al. BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis. Hum Reprod Update. 2013;19(3):221-231.
6. Hammiche F, Laven JS, Twigt JM, et al. Body mass index and central adiposity are associated with sperm quality in men of subfertile couples. Hum Reprod. 2012;27(8):2365-2372.
7. Hammoud AO, Gibson M, Peterson CM, Meikle AW, Carrell DT. Impact of male obesity on infertility: a critical review of the current literature. Fertil Steril. 2008;90(4):897-904.
8. Hammoud AO, Wilde N, Gibson M, et al. Male obesity and alteration in sperm parameters. Fertil Steril. 2008;90(6):2222-2225.
9. Chavarro JE, Toth TL, Wright DL, Meeker JD, Hauser R. Body mass index in relation to semen quality, sperm DNA integrity, and serum reproductive hormone levels among men attending an infertility clinic. Fertil Steril. 2010;93(7):2222-2231.
10. Jensen TK, Andersson AM, Jorgensen N, et al. Body mass index in relation to semen quality and reproductive hormones among 1,558 Danish men. Fertil Steril. 2004;82(4):863-870.
11. Aggerholm AS, Thulstrup AM, Toft G, Ramlau-Hansen CH, Bonde JP. Is overweight a risk factor for reduced semen quality and altered serum sex hormone profile? Fertil Steril. 2008;90(3):619-626.
12. MacDonald AA, Herbison GP, Showell M, Farquhar CM. The impact of body mass index on semen parameters and reproductive hormones in human males: a systematic review with meta-analysis. Hum Reprod Update. 2010;16(3):293-311.
13. Reis LO, Zani EL, Saad RD, et al. Bariatric surgery does not interfere with sperm quality--a preliminary long-term study. Reprod Sci. 2012;19(10):1057-1062.
14. Hakonsen LB, Thulstrup AM, Aggerholm AS, et al. Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men. Reprod Health. 2011;8:24.
15. Facchiano E, Scaringi S, Veltri M, et al. Age as a predictive factor of testosterone improvement in male patients after bariatric surgery: preliminary results of a monocentric prospective study. Obes Surg. 2013;23(2):167-172.
16. Sermondade N, Massin N, Boitrelle F, et al. Sperm parameters and male fertility after bariatric surgery: three case series. Reprod Biomed Online. 2012;24(2):206-210.
17. National Institutes of Health; National Heart, Lung, and Blood Institute; and North American Association for the Study of Obesity. The Practical Guide: Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NIH Publication No. 00-4084. October 2000.
18. World Health Organization. WHO Laboratory Manual for the Examination of Human Semen and Sperm-Cervical Mucus Interaction, 5th Edition. Cambridge, UK: Cambridge University Press; 2010.