Body fat ratio and gallstone disease risk: A cross-sectional study identifying a nonlinear risk threshold at 29.1

ObjectiveTraditional indicators of obesity, such as body mass index (BMI), fail to precisely capture the independent impact of fat distribution on gallstone disease (GSD). This study aimed to investigate the nonlinear association between body fat ratio (BFR) and the risk of GSD and to identify a critical threshold value.MethodWe conducted a cross-sectional observational analysis of 1952 adults from the 2017-2018 National Health and Nutrition Examination Survey (NHANES). BFR was measured by dual-energy X-ray absorptiometry, and GSD was defined by standardized questionnaire data. Weighted logistic regression, restricted cubic spline (RCS), and threshold effect models were employed to examine the association between BFR and GSD risk, as well as to determine the inflection point.ResultsA significant J-shaped nonlinear association was observed between BFR and GSD risk (P for non-linearity < 0.001). Threshold analysis identified 29.1% (95% CI: 27.5-30.7%) as the critical inflection point, beyond which each 1% increase in BFR was associated with a 14% higher odds of GSD (OR = 1.14, 95% CI: 1.09-1.19). After multivariate adjustment, each additional 1% increase in BFR remained independently associated with a 7% increased risk (OR = 1.07, 95% CI: 1.02-1.13). Compared with participants in the lowest quartile, those in the highest quartile (BFR≥39.2%) exhibited a 2.66-fold higher risk of GSD. Subgroup analyses demonstrated stronger associations in males (OR ≈ 1.12 per 1% BFR increase) and Hispanics (OR ≈ 1.20 per 1% BFR increase).ConclusionsBFR of ≥29.1% represents a critical threshold beyond which GSD risk significantly increases. These findings suggest an association that warrants further investigation into whether routine monitoring of BFR could serve as a valuable screening tool in high-risk populations, and precise intervention strategies should consider gender and ethnic differences to effectively mitigate metabolic-related gallstone disease.