Association between body mass index and semen quality: a systematic review and meta-analysis

The continuous decline of human semen quality during the past decades has drawn much concern globally. Previous studies have suggested a link between abnormal BMI and semen quality decline, but the results remain inconsistent. This systematic review and meta-analysis aimed to evaluate the association between body mass index (BMI) and semen quality. We searched PubMed, Embase, and Web of Science for eligible studies from inception to April 17, 2022. We considered men with BMI < 25.0 kg/m2 as the reference and calculated the pooled weighted mean difference of men with overweight (BMI 25.0–29.9 kg/m2), obesity (BMI ≥ 30.0 kg/m2), class I obesity (BMI 30.0–34.9 kg/m2), and class II/III obesity (BMI ≥ 35.0 kg/m2). A total of 5070 articles were identified, of which 50 studies were included (71,337 subjects). Compared with men with BMI < 25.0 kg/m2, men with obesity had an average reduction of 0.24 ml in semen volume, 19.56 × 106 in total sperm number, 2.21% in total motility, 5.95% in progressive motility, and 1.08% in normal forms, respectively, while men with overweight had an average reduction of 0.08 ml in semen volume and 2.91% in progressive motility, respectively. The reduction of semen quality was more pronounced among men with obesity than that among men with overweight. Moreover, significant reductions in semen quality were identified in men with different classes of obesity, which were more pronounced in men with class II/III obesity than that in men with class I obesity. Across men from the general population, infertile or subfertile men, and suspiciously subfertile men, we identified significant semen quality reductions in men with obesity/overweight. In conclusion, obesity and overweight were significantly associated with semen quality reductions, suggesting that maintaining normal weight may help prevent semen quality decline.