BackgroundThe role of body mass index (BMI) in basal cell carcinoma (BCC) risk remains controversial, and limited information is available regarding the relationship between other physical measurements and BCC. Several recent studies have found a positive effect of adiposity on improved survival when obesity was determined solely by BMI (the "obesity paradox"). We hypothesize that body fat percentage (BFP) may serve as a more sensitive risk factor for BCC than BMI. MethodsThe study conducted a retrospective analysis of clinical data from two distinct centers in China. Individual patient-level data were obtained from medical record reviews spanning January 1, 2015, to December 31, 2022. Associations with outcomes were analyzed using univariate and stratified analyses and assessed using multiple logistic regression with adjustment for confounding factors. Additionally, we performed a meta-analysis to further test the observations in our study. ResultsA total of 337 patients, ranging in age from 50 to 91 years, with a mean age of 66.88 (standard deviation 10.16), were included. We observed no significant association between BMI and BCC after adjusting for confounders (OR: 0.71, 95 % CI: 0.36–1.40, P = 0.3186). There was also no convincing effect in a meta-analysis (n = 158,741) (OR: 0.99, 95 % CI: 0.93–1.06, P = 0.8). Furthermore, BFP was found to be associated with BCC (OR: 2.64, 95 % CI: 1.17–5.97, P = 0.0196), supported by strong clinical evidence. ConclusionsOur study supports the hypothesis that BFP is superior to BMI in assessing BCC risk. Multiple logistic regression analyses, coupled with meta-analysis, provided robust evidence that BFP is a sensitive risk factor for BCC, while BMI appears unrelated to risk. According to these findings, routine healthcare practices could benefit from utilizing BFP measurements. The reduction of body fat percentage in low-fat diets may be beneficial for adjuvant treatment of BCC.