In recent decades, the global obesity epidemic has paralleled a decrease in sperm quality 1, 2, 3, 4, 5, 6, 7. In addition to genetic factors, lifestyle, metabolic disorder, infection and environment also affect sperm motility. Nowadays, it is generally accepted that asthenospermia, which leads to male infertility, is a complex disease in which various etiologic factors are involved. Thereof, BMI is a risk factor for asthenospermia only in men with enterotype P, but not in men with enterotype B. however, sperm quality was not associated with overweight/obese in men with enterotype B. In our study, overweight/obese men with enterotype P were found to have poorer sperm quality. This study is tried to introduce enterotypes as a population-based individualized classification index to investigate the correlation between BMI and asthenospermia. However, in enterotype B group (P < 0.01), obesity was not a risk factor for asthenospermia, where no significant difference between obesity and sperm quality parameters was observed. In enterotype P, body mass index, as a diagnostic indicator of a reduced rate of forward progressive sperm motility and a decreased rate of decreased total sperm motility, had AUC values of 0.627 (P = 0.001) and 0.675 (P < 0.0001), respectively, which were significantly higher than the predicted values in all patients. Obesity was also an independent risk factor (OR 3.131 95% CI 1.749–5.607 P < 0.001) after adjusting follicle-stimulating hormone.

In enterotype P group (P/B ≥ 0.01), obesity was a risk factor for a reduced rate of forward progressive sperm motility (odds ratio 3.350 95% confidence interval 1.881–5.966 P < 0.001), and a reduced rate of total sperm motility (OR 4.298 95% CI 2.365–7.809 P < 0.001). The ratio between Prevotella and Bacteroides abundance, P/B, was used as a simplified way to distinguish the predominant enterotype.

Prevotella and Bacteroides were analyzed in 407 samples of stool, including 178 men with enterotype B (61 normal, 117 overweight/obese) and 229 men with enterotype P (74 normal, 155 overweight/obese). A study was designed at the Center of Reproductive Medicine, Shengjing Hospital of China Medical University and Jinghua Hospital of Shenyang.

The essence of enterotypes is stratifying the entire human gut microbiome, which modulates the association between diet and disease risk.

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