Metabolically healthy obesity linked to poorer sperm quality in Taiwanese men

Men with metabolically healthy obesity (MHO) — obesity without the overt metabolic abnormalities that define metabolic syndrome — showed significantly lower sperm concentration and reduced normal sperm morphology compared with metabolically healthy normal-weight men, according to a study of 8,393 Taiwanese men published in BMC Endocrine Disorders. The finding challenges the assumption that a favorable metabolic profile shields obese individuals from the reproductive effects of excess weight.

The researchers analyzed data from men who attended a private health examination in Taiwan between 2010 and 2016. Semen parameters were evaluated according to World Health Organization guidelines, and participants were classified into four metabolic–obesity phenotypes based on their obesity status and the presence or absence of metabolic syndrome components. This design allowed the team to separate the effects of obesity itself from those of overt metabolic dysfunction such as dyslipidemia.

Using multivariable linear and logistic regression, the investigators assessed associations between the obesity phenotypes and sperm parameters while adjusting for demographic, inflammatory, and lipid-related metabolic variables. Even after this full adjustment, MHO remained independently associated with an increased likelihood of falling in the lowest quartile of both sperm concentration and normal morphology.

Notably, no significant associations with sperm quality were observed among men with metabolically unhealthy obesity in this dataset. The authors suggest that obesity-related lipid dysregulation and adipose tissue–derived metabolic alterations may contribute to sperm dysfunction even when overt metabolic syndrome is absent, meaning that relatively favorable lipid profiles in MHO do not appear to confer protection against obesity-associated sperm impairment.

As a cross-sectional analysis of men attending a single private health examination center, the study identifies associations rather than proving causation, and the unexpected pattern in the metabolically unhealthy obesity group warrants further investigation. Nevertheless, the results indicate that excess adiposity may affect male fertility through pathways that operate independently of clinically recognized metabolic disease.

Subject of Research: The association between metabolically healthy obesity and sperm quality in Taiwanese men

Article Title: The relationship between metabolically healthy obesity and sperm quality in Taiwanese men

Article References: Chen, Y.-Y., Peng, T.-C., Kao, T.-W., & Tsao, Y.-T. (2026). The relationship between metabolically healthy obesity and sperm quality in Taiwanese men. BMC Endocrine Disorders. https://doi.org/10.1186/s12902-026-02686-0

Image Credits: AI Generated

DOI: 10.1186/s12902-026-02686-0

Keywords: metabolically healthy obesity, sperm quality, sperm concentration, sperm morphology, obesity, metabolic syndrome, male fertility, Taiwan, lipid metabolism, cross-sectional study, BMC Endocrine Disorders, relationship