Ultrasound-detected hepatic steatosis in normal-weight adults without diagnosed diabetes or conventional hypertension: burden and metabolic phenotype in 93,562 health examinees

Normal body mass index (BMI) may lower clinical suspicion of hepatic steatosis. We quantified the burden and metabolic phenotype of ultrasound-detected steatosis among normal-weight Chinese adults without diagnosed diabetes or conventional hypertension. This single-center cross-sectional study used 2024 health-examination data. Of 149,003 adults screened, 93,562 met all criteria: fasting glucose < 6.1 mmol/L, no diagnosed diabetes or hypertension, blood pressure < 140/90 mmHg, abdominal ultrasonography, and complete measurements. Primary analyses used Chinese normal weight (BMI 18.5–<24 kg/m²). Participants were cross-classified by normal weight vs. BMI ≥ 24 kg/m² and steatosis. Associations were evaluated with logistic regression, quartiles, and restricted cubic splines, adjusting for age, sex, smoking, current alcohol use, BMI, and systolic and diastolic blood pressure. Sensitivity analyses used alternative BMI, glucose, and blood-pressure thresholds and excluded alcohol users or hepatitis-seropositive participants. Hepatic steatosis was detected in 33,042 participants (35.3%). Among 54,438 normal-weight participants, 9,700 had steatosis (17.8%, 95% confidence interval [CI] 17.5%–18.1%) and accounted for 29.4% of all cases. Participants with normal weight and steatosis had greater waist circumference and less favorable lipid, uric-acid, liver-enzyme, and insulin-resistance-related measures than those without. After adjustment, the normal-weight steatosis group had higher triglycerides (TG), TG/high-density lipoprotein cholesterol (TG/HDL-C) ratio, triglyceride-glucose index (TyG), uric acid, alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), and fasting glucose and lower HDL-C than the BMI ≥ 24 kg/m² group without steatosis, despite lower waist circumference (WC) and TyG-WC (TyG × WC). In fully adjusted marker-specific models, odds ratios (ORs) per 1 standard deviation (SD) were 3.42 (95% CI 3.29–3.56) for TyG-WC, 2.43 (2.36–2.50) for TG/HDL-C, 2.33 (2.26–2.39) for TyG, 2.25 (2.18–2.31) for TG, and 2.06 (1.98–2.14) for WC. The quartile 4 vs. quartile 1 TyG-WC OR was 23.39 (19.91–27.49). The association was stronger in women than men (OR 3.56 vs. 3.12 per 1 SD; P for interaction < 0.01) and was unchanged after excluding alcohol users or seropositive participants. Ultrasound-detected hepatic steatosis was common and metabolically unfavorable among normal-weight adults without diagnosed diabetes or hypertension. Normal BMI alone should not be assumed to exclude steatosis. The reported markers should be interpreted as correlates rather than causal predictors or substitutes for liver imaging.