Non-alcoholic fatty liver disease may develop in individuals with normal body mass index

Although non-alcoholic fatty liver disease (NAFLD) is associated with obesity and metabolic syndrome (MS), it may also be present in lean individuals. We evaluated the characteristics of NAFLD patients, focusing on those with normal body mass index (BMI).

One hundred and sixty-two of 185 consecutive NAFLD patients were included (23 were excluded due to missing data). NAFLD diagnosis required elevated ALT and/or GGT, hepatic steatosis on ultrasonography and no other cause of liver disease. Demographic, clinical, somatometric and laboratory characteristics were recorded. BMI <25 kg/m2 was considered normal.

Normal BMI was present in 12% of patients. Patients with normal compared to those with increased BMI had numerically but not significantly lower prevalence of diabetes mellitus (6% vs. 15%, p=0.472), arterial hypertension (17% vs. 29%, p=0.276) and MS (20% vs. 41%, p=0.160). Normal BMI NAFLD patients met no criterion of MS more frequently (43% vs. 2%, p<0.0001) and had smaller waist circumference (94±6 vs. 108±10 cm, p<0.001), higher median levels of ALT (92 vs. 62 IU/L, p=0.032) and AST (45 vs. 37 IU/L, p=0.036) and relatively lower fasting glucose levels (98±22 vs. 106±29 mg/dL, p=0.052), but similar levels of HDL, LDL and triglycerides.

Approximately 1 of 8 NAFLD patients coming to the tertiary liver center has normal BMI. These patients do not necessarily have insulin resistance associated metabolic disorders, but they have higher levels of ALT/AST than the overweight or obese NAFLD patients.