Meta AnalysisHumann = 8,443 men (3,467 normal BMI, 3,444 overweight, 1,532 obese)2025China
BMI is associated with sperm quality and sex hormones in men: a meta-analysis.
Plain-language summary
This meta-analysis (a study that statistically pools many earlier studies) looked at how body mass index (BMI, a weight-for-height number used to flag over- or under-weight) relates to sperm quality and male sex hormones. It combined 14 studies covering 8,443 men across normal-weight, overweight, and obese groups. Higher BMI was linked to worse sperm concentration, movement, and shape, along with shifts in total testosterone, FSH (follicle-stimulating hormone, the pituitary signal that tells the testicles to make sperm), and LH (luteinizing hormone, the pituitary signal that tells the testicles to make testosterone). The authors argue weight belongs in any male-fertility workup.
Key findings
- Higher BMI was linked to worse sperm shape, movement, concentration, and total count.
- Overweight and obese men had lower total testosterone and altered FSH and LH levels compared to normal-weight men.
- The study pooled data from 14 studies involving 8,443 men.
How to analyze the study yourself
- Study type
- Meta-analyses pool many studies to spot patterns, but they rely on the quality of the original research and cannot prove cause and effect.
- Population
- Adult men from studies that measured BMI and sperm or hormone levels.
- Funding
- Not reported
- Watch for
- This study found that a higher BMI tracked with worse sperm quality and a knocked-off-balance set of reproductive hormones. If you are trying to conceive, getting to a healthy weight is worth the effort.