Sex is a critical biological variable that influences disease incidence, progression, and therapeutic responses; therefore, it must be incorporated into biomedical research. Despite this, most mouse studies historically have not compared animals by sex. Recently, growing evidence has indicated that sex-specific analyses are important in obesity and metabolic disorders. The ob/ob mouse is a widely used model for metabolic disease research; however, sex differences in plasma biomarkers have not been fully characterized in this model. In this study, male and female ob/ob mice at 8 weeks of age exhibited comparable body weight, blood glucose levels, and adipose tissue mass. Plasma proteomics analysis using the Olink platform revealed that 27% (23/84) of quantified proteins exhibited sex differences, with 91% (21/23) of these proteins elevated in females. Notably, Enolase 2 (ENO2), also known as neuron-specific enolase (NSE), was consistently elevated in female ob/ob mice and showed a similar sex-associated pattern in female patients with non-alcoholic steatohepatitis (NASH). While the human NASH data provide correlative support rather than direct clinical validation, these observations underscore the importance of considering sex as a biological variable in metabolic disease research. Incorporating sex-specific biomarker profiles may help refine mechanistic interpretation and inform future studies toward personalized therapeutic approaches.