Obesity-related poor sperm quality is a significant public health issue, acting as a major contributor to male infertility. Dietary intervention has emerged as an effective strategy to manage obesity and improve sperm quality. Soluble dietary fiber (SDF), an essential nutritional component, plays a crucial role in regulating host health. Notably, insufficient SDF intake has been associated with both obesity and low sperm motility. However, the effect of SDF supplementation on sperm quality in males with obesity remains unclear. Thus, we conducted a randomized, placebo-controlled study to investigate the effect of SDF supplementation on sperm quality in males with obesity.

Inclusion Criteria:

1. Male, aged 18-60 years；
2. Diagnostic criteria for obesity: BMI ≥ 28 kg/m² and body fat percentage ≥ 25%;
3. Semen samples can be collected, and sperm concentration > 0.

Exclusion Criteria:

1. Spermatogenic dysfunction caused by non-obesity factors;
2. Severe systemic diseases such as cardiovascular/cerebrovascular, hepatic/renal disorders, malignant tumors, uncontrolled diabetes, or thyroid diseases;
3. Recent usage of medications/supplements affecting spermatogenesis or gut microbiota ;
4. Lifestyle factors potentially impairing sperm quality or severe gastrointestinal disorders;
5. Poor compliance, planned imminent fertility, or history of bariatric surgery/weight-loss medications;
6. Significant dietary changes within the past three months.