Obesity (body mass index, BMI > 30 kg/m2) has become a global epidemic affecting more than 600 million adults worldwide; in 2018, 43% of American men were obese. As the prevalence of obesity has increased steadily over more than 3 decades, a concurrent decline in semen quality has been described. The mechanisms by which obesity may result in diminished semen quality and male factor infertility include hormone changes, sexual dysfunction, or other medical issues including diabetes mellitus, sleep apnea or scrotal hyperthermia due to body habitus.
Obesity in men is associated with lower sperm counts and poorer sperm motility (“swimming capability”) in many published research studies and an inverse relationship between BMI and testosterone is well-established. Male obesity may also alter sperm function, increase sperm DNA damage, decrease sperm mitochondrial activity, and induce seminal oxidative stress.
In obese men, the scrotum remains in closer contact with surrounding tissue than in normal-weight men, predisposing to increased scrotal temperature that may adversely affect semen parameters. Unfortunately, treatments aimed at lowering scrotal temperature (‘‘scrotal hypothermia’’) or reducing the amount of scrotal fat are impractical and unproven. Fertility challenges may be a unique motivator for obese men to lose weight. Weight loss convincingly results in increased testosterone levels and improvements in sexual function. The interplay between weight loss and sperm production is less definitive due to a scarcity of data regarding changes in semen parameters after weight loss in men but do suggest improved sperm counts with weight loss. When a couple is trying to conceive, both partners should try to do everything they reasonably can to optimize their fertility potential including aiming for a healthy weight through healthful diet and exercise. An adjunct to these efforts would be a male fertility-oriented supplement.
