Obesity and Male Infertility
Effect of Male Obesity on Fertility in the General Population
In a secondary analysis of the Agricultural Health Study, Sallmén et al found that male BMI was associated with infertility with an odds ratio (OR) of 1.12 (95% confidence interval [CI], 1.01 to 1.25), after correction for female BMI, male and female age, smoking status, alcohol use, and exposure to solvents and pesticides. There was a dose-effect relation with maximal effect in the BMI class 32 to 43 kg/m.
Ramlau-Hansen et al analyzed data extracted from the Danish National Birth Cohort of 47,835 women. In this study, overweight (BMI: 25 to 29.99 kg/m) and obese (≥30 kg/m) men were more likely to report infertility with ORs of 1.15 (95% CI, 1.09 to 1.22) and 1.49 (95% CI, 1.34 to 1.64), after correction for female BMI and the age of both partners.
Nguyen et al, in a secondary analysis of the Norwegian Mother and Child cohort study, showed the OR for infertility was 1.19 (95% CI, 1.03 to 1.62) for overweight men (BMI: 25 to 29.9 kg/m) and 1.36 (95% CI, 1.12 to 1.62) for obese men, after correcting for coital frequency, female BMI, male and female age, smoking status, and various risk factors for female infertility.
In a study of 91 male Japanese auto workers, Ohwaki and Yano found an increased incidence of not fathering a child per year of marriage with increasing male BMI. In men presenting with wives to the delivery suites or to a fertility clinic, a history of paternity was associated with lower BMI when compared with no history of paternity.
Although current BMI in men appears to be correlated to reduced fertility, increased weight during adolescence was also be correlated with reduced fertility in adulthood. Jokela et al studied the effect of increased weight in adolescence on future fertility in 583 male participants. The predicted number of future children was 1.46 for normal weight, 1.4 for overweight, and 0.99 for the obese male adolescents. The association between the adolescent's skinfold thickness and number of future children confirmed the prediction.
These studies suggest a small dose-related effect of obesity on male fertility. Despite the small magnitude of the effect, the impact of increased weight on male fertility can be significant when evaluated at the population level.
Effect of Male Obesity on Success of Treatment of Infertile Couple
The effect of male obesity on the outcome of fertility therapy has been described infrequently. Bakos et al described the effect of male obesity on the outcome of treatment in couples undergoing in vitro fertilization (IVF). In this study including 305 couples undergoing an initial IVF treatment, the effect of paternal obesity on embryo quality and pregnancy rate was analyzed. Men with normal BMI were found to have a higher sperm concentration than overweight, obese, and morbidly obese men. Morbidly obese men had a higher rate of the prescribed use of ICSI for fertilization. After treatment, there was a higher rate of blastulation in couples with normal weight men when compared with those with obese and severely obese men. There was also a linear reduction in chemical and clinical pregnancy rates, and live-birth rates with increasing BMI in the male partners.
Braga et al examined the effect of food intake and social habits in men on the success of IVF with ICSI. A total of 250 men were approached with questionnaires regarding their food intake. This exposure data set was correlated with fertilization, implantation, pregnancy, and miscarriage rates. In this study, male BMI was correlated negatively to sperm concentration and motility. There was no association between male BMI and rates of fertilization, implantation, pregnancy, or miscarriage.
In a retrospective review that addressed records of men undergoing microsurgical subinguinal varicocelectomy, Pham and Sandlow analyzed records of 143 men. The percentage of men that improved after surgery were 71.1% in the normal weight men, 61% in the overweight category, and 58.7% in the obese men; however, the difference was not statistically significant (p = 0.21). There was also no difference on the percentage improvement in sperm concentration, motility, and progressive motility in men in the three weight categories. This study reviewed a small number of cases and could lack adequate power to demonstrate a difference. Of note, the testosterone levels were not significantly different in three groups, despite the known relation between male BMI and testosterone levels, favoring a lack of power in this study.