A Randomized Controlled Trial of Standard Behavioral Weight-Loss Intervention on Reproductive Parameters in Obese Men

Ruby H. N. Nguyen, Ph.D.
Division of Epidemiology & Community Health, University of Minnesota

Strong evidence indicates that women with excess body weight are more likely to be sub-fertile and that the probability of pregnancy may increase with weight loss. While scarce data exist for making a similar claim for obese men, small studies have reported poor parameters of reproductive hormones important to spermatogenesis such as testosterone and testosterone-to-estradiol ratio. These findings are plausible since men’s excess weight may disturb the hypothalamic-pituitary-gonadal axis, resulting in adverse changes to reproductive hormones, not unlike what occurs in women; these alterations may then affect spermatogenesis. Some studies have indicated that extreme weight loss in obese men may normalize some hormone values, but no data on changes to semen exist. We therefore propose to determine whether a standard behavioral weight loss intervention in obese men is associated with improvement of reproductive hormones and semen parameters to a level conducive to normal spermatogenesis. The goal of this standard behavioral treatment intervention is caloric reduction and increased exercise for men with BMI ≥ 30, resulting in a loss of 8 to 10% of the man’s baseline weight. Eligible participants will be recruited from the Reproductive Medicine Center at Fairview Riverside. Twenty men will be randomized into an intervention arm, and 20 into a control arm, providing > 90% power to detect a difference. Baseline semen and hormone levels will be abstracted from the medical record, then blinded semen and reproductive hormone analysis will be determined at mid-trial (6 months) and the end of the trial (12 months). For hormone values, fresh peripheral venous blood will be collected to determine total testosterone, estradiol, and sex hormone binding globulin. Criteria for semen analysis will be taken from WHO guidelines, including: semen volume, sperm concentration, motility, and morphology. Our primary analyses will determine whether hormone and semen values in the weight-loss intervention arm differ at 6- and 12- months from their baseline values (paired test), or whether their mean scores differ from that of the control group at similar times. We also aim to determine whether sexual/erectile function scores modify observed associations. Determination of feasibility and results from the statistical analyses will be used to inform an obesity-related R-series NIH grant application.