To examine the association between body weight and measures of male reproductive potential. Cross-sectional study. Fertility clinic in an academic medical center. Four hundred eighty-three male partners of subfertile couples. None. Standard semen analysis, sperm DNA fragmentation, and serum levels of reproductive hormones. As expected, body mass index (BMI) was positively related to estradiol levels and inversely related to total testosterone and sex hormone-binding glogulin (SHBG) levels. There was also a strong inverse relation between BMI and inhibin B levels and a lower testosterone:LH ratio among men with a BMI > or = 35 kg/m(2). Body mass index was unrelated to sperm concentration, motility, or morphology. Ejaculate volume decreased steadily with increasing BMI levels. Further, men with BMI > or = 35 kg/m(2) had a lower total sperm count (concentration x volume) than normal weight men (adjusted difference in the median [95% confidence interval] = -86 x 10(6) sperm [-134, -37]). Sperm with high DNA damage were significantly more numerous in obese men than in normal-weight men. These data suggest that despite major differences in reproductive hormone levels with increasing body weight, only extreme levels of obesity may negatively influence male reproductive potential. Copyright 2010 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.
