Abdominal Obesity, Testosterone Deficiency and Sedentary Lifestyle in Young Men from the General Population: The Relationship with Semen Quality, Hormonal and Metabolic Status

Background: The demographic crisis observed in industrialized countries has been accompanied by a decline in the reproductive potential of human populations. One of the causes for the global deterioration in men's reproductive health is adiposity and sedentary lifestyle, leading to reduced fertility and a decrease in androgen status. The aim of the study was to assess the association between abdominal obesity and semen parameters, including sperm DNA fragmentation, as well as key indicators of hormonal and metabolic status in young men from the general population. Methods: Our cross-sectional study was conducted among Russian and Belarusian men living in six cities. The examination of men (n=1283, median age 23 years) included questionnaires, anthropometry, collection of peripheral blood and semen samples. Semen analysis was conducted according to WHO guidelines (WHO, 2010; 2021). Sperm DNA fragmentation index (DFI) was evaluated using the SCSA method. The serum and seminal zinc concentration was determined using spectrophotometry and direct calorimetry. Reproductive hormonal and metabolic levels were measured by commercial kits. The waist circumference (WC) was used as a surrogate marker of adiposity. Participants were allocated to three phenotypes: non-obese (control, WC< 94 cm), excess abdominal fat (94≤WC< 102 cm) and abdominal obesity (WC≥102 cm). Results: In our study population, 85.8% of participants were young (under 30 years of age), 8.6% had excess abdominal fat, 5.9% - abdominal obesity (AO); 65.2% - normozoospermia. Men with AO were characterized by a decrease in semen volume, total sperm count, sperm concentration and progressive motility compared to the non-obese control. DFI was significantly higher in obese compared to non-obese men. Obese participants had significantly lower testosterone and inhibin B levels, but higher FSH and leptin levels compared to non-obese men. Men with AO had elevated serum zinc levels, but reduced seminal zinc content. Abdominal obesity was also associated with significant metabolic changes, in particular, with increased levels of triglycerides, total cholesterol, low-density lipoproteins, fasting glucose and uric acid. Obesity-related testosterone deficiency (serum testosterone level ≤12.1 nmol/L) was detected in 38.4% of obese men and significantly aggravated the negative impact of adiposity on DFI, FSH, testosterone, leptin levels, and the metabolic status. Physically active obese men (who engaged in recreational sports or physical labor) demonstrated reduced anthropometric indicators of obesity, increased testosterone levels, as well as improved carbohydrate and lipid metabolism compered to sedentary obese men. Conclusion: AO is accompanied by a decrease in the activity of Leydig and Sertoli cells, as well as an imbalance of the hypothalamic-pituitary-testicular axis and metabolic status. AO associated with testosterone deficiency or a sedentary lifestyle is a potential risk factor for weakening male reproductive health. However, its negative effects can be partially mitigated by moderate physical activity. In the long term, without lifestyle correction and with persistent abdominal obesity, obese men are not protected from infertility.