To investigate the prevalence and characteristics of children with nonalcoholic fatty liver disease (NAFLD) who reduce their body mass index (BMI) z-score (BMIz) by >.25, a goal in obesity medicine, and to determine the BMIz decrease needed for serum aminotransferase normalization.

This retrospective, single-center study included patients aged <18 years followed for NAFLD. Patients who had undergone weight loss surgery or had other reasons for weight loss/gain were excluded. Logistic regression was used to determine the odds of achieving a BMIz change of >−.25, as well as predictors of this outcome.

Of the 784 children who met the study criteria (median age, 13 years; 66% male; 24% Hispanic), 541 had a lowest BMIz at >90 days following the baseline clinic visit. Of these children, 168 (31%) had a BMIz change of >−.25 from baseline over a median of 367 days (IQR, 201-678 days). Decreases in serum aminotransferase and lipid levels were seen in both groups (with and without a BMIz change of >−.25); however, these decreases were more pronounced in children who achieved a BMIz drop of >.25. Hemoglobin A1c concentration did not change in either group. Young age (OR, .861; 95% CI, .81-.92; P < .01) and non-Hispanic ethnicity (OR of non-Hispanic vs Hispanic, .61; 95% CI, .38-.97; P < .04) were predictors of a BMIz change >−.25. The BMIz decrease associated with normalization of serum alanine aminotransferase was .27.

A BMIz reduction of >.25 is associated with significant changes in serum aminotransferase levels. These findings can further guide the clinical management of children with NAFLD.