Background Non-alcoholic fatty liver disease (NAFLD) has a high prevalence in obese children. Lifestyle intervention is the primary treatment for NAFLD. However, limited data are available regarding the efficacy of lifestyle interventions.

Objectives To prospectively determine the efficacy of a lifestyle intervention programme on NAFLD in severely obese children and identify the clinical parameters related to improvement in NAFLD.

Methods Children admitted to a lifestyle intervention programme were screened for NAFLD. Steatosis was defined as increased echogenicity of the liver on ultrasonography. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were used as surrogate markers for steatohepatitis. The lifestyle intervention programme consisted of physical exercise, dietary counselling and behavioural counselling for a period of 6 months.

Results 144 children were included with a mean age of 14.1 (±2.3) years, BMI z-score of 3.35 (±0.40) kg/m². Lifestyle intervention significantly reduced the prevalence of steatosis (31.2–11.9%, p<0.001) and the prevalence of elevated serum ALT (25.7–11.1%, p<0.001) and serum AST (13.3–4.3%, p<0.002). In multivariate regression analysis, improvement in the degree of steatosis and decrease in ALT and AST were all significantly related to improvement in insulin resistance. Improvement in insulin resistance only explained a small part of the observed changes in transaminases.

Conclusions A lifestyle intervention of 6 months is moderately effective in improving NAFLD in severely obese children. Improvement in insulin resistance is the clinical parameter most strongly associated with improvement in NAFLD. Other factors related to the successful treatment of NAFLD need to be identified so that these can be a focus for new lifestyle and drug interventions.