Risk and protective factors of non-alcoholic fatty liver disease in paediatric obesity: A nationwide nested case-control study.

Not all children with obesity carry a similar risk of non-alcoholic fatty liver disease (NAFLD). We investigated the effect of obesity severity, metabolic risk parameters, and obesity treatment outcome on later risk of NAFLD in paediatric obesity. We conducted a nested case-control study of children and adolescents enrolled in the Swedish Childhood Obesity Treatment Register (BORIS) (2001-2016). NAFLD was ascertained from the National Patient Register. Five controls per case were matched by sex and age at index date and at the obesity treatment initiation. Seventy-six pairs (n cases = 76, n controls = 241) were included in the analysis (29% females, mean age at obesity treatment initiation was 10.8 ± 3.07 years). Mean age of NAFLD diagnosis was 14.2 ± 3.07 years. The risk for NAFLD increased with severe obesity (odds ratio [OR]: 3.15, 95% confidence interval [CI]: 1.69-5.89), impaired fasting glucose (OR: 5.29, 95% CI: 1.40-20.06), high triglycerides (OR: 2.33, 95% CI: 1.22-4.43) and weight gain (OR: 4.67, 95% CI: 1.51-14.49 per body mass index standard deviation score [BMI SDS] unit). Relative weight loss of at least 0.25 BMI SDS units reduced NAFLD risk independently of other risk factors (OR: 0.09, 95% CI: 0.01-0.56). Severe obesity, impaired fasting glucose and high triglycerides are risk factors for future NAFLD in paediatric obesity. Successful obesity treatment almost eliminates the risk for NAFLD independently of obesity severity, IFG and high triglycerides.