Beyond BMI: central obesity identifies overlooked fatty liver disease risk in adults with normal body mass index undergoing routine health examinations

Figures

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  Figure 1. Prevalence of ultrasound-diagnosed fatty liver disease across BMI-waist phenotypes. Bars show the absolute prevalence of ultrasound-diagnosed fatty liver disease across the four BMI-waist phenotype groups, and error bars indicate 95% confidence intervals. The figure shows a graded prevalence pattern, with the lowest prevalence in participants with normal BMI/no central obesity, similar prevalence in participants with normal BMI/central obesity and overweight-obesity/no central obesity, and the highest prevalence in participants with both overweight-obesity and central obesity. BMI categories were defined according to Chinese adult criteria. Central obesity was defined as waist circumference ≥90 cm in men and ≥85 cm in women.

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  Figure 2. Adjusted fitted probability of ultrasound-diagnosed fatty liver disease according to waist circumference among adults with normal BMI. The solid curve shows the adjusted fitted probability of ultrasound-diagnosed fatty liver disease across waist circumference values among participants with normal BMI. The shaded area indicates the 95% confidence interval. Estimates were derived from a multivariable logistic regression model using natural cubic splines for waist circumference with three degrees of freedom, corresponding to two internal knots placed at the 33.3rd and 66.7th percentiles of waist circumference. The model was adjusted for sex, age, smoking status, drinking status, and physical activity. Predictions were displayed across the 2.5th to 97.5th percentile range of waist circumference to reduce instability at the distributional extremes. The likelihood ratio test did not show evidence of nonlinearity (P for nonlinearity = 0.220).

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  Figure 3. Subgroup analysis of the association between central obesity and ultrasound-diagnosed fatty liver disease among adults with normal BMI. Points represent adjusted odds ratios, and horizontal lines indicate 95% confidence intervals for the association between central obesity and ultrasound-diagnosed fatty liver disease within each subgroup. Models were adjusted for age, sex, smoking status, drinking status, and physical activity, except for the corresponding stratifying variable. P-values for interaction were calculated using likelihood ratio tests comparing models with and without the interaction term. The figure shows directionally consistent associations across subgroups defined by sex, age group, hypertension, and dysglycemia, with no statistically significant interaction observed.