['Active surveillance (AS) is an expectant management strategy for prostate cancer (PCa). The impact of obesity on progression is not well characterized in this population.', 'To determine if obesity is associated with progression in men on AS for low-risk PCa.', 'Men undergoing AS for low-risk PCa (no Gleason pattern ≥4, three or fewer cores involved or one-third or less of the total number of cores involved, and no core with >50% cancer involvement) were identified at our institution.', 'The outcomes were pathologic progression (defined as no longer meeting low-risk criteria on follow-up biopsy) and therapeutic progression (defined as intent to initiate active treatment). Kaplan-Meier curves and multivariable logistic regression and Cox proportional hazards models were used, with separate models for reclassification at confirmatory biopsy (first biopsy after diagnostic biopsy) and progression beyond confirmatory biopsy.'] Is obesity associated with risk of progression for low-risk prostate cancers managed expectantly?