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Mediterranean diet intervention to prevent progression of pediatric nonalcoholic fatty liver disease (NAFLD): a systematic review of dietary and lifestyle studies
Mediterranean diet intervention to prevent progression of pediatric nonalcoholic fatty liver disease (NAFLD): a systematic review of dietary and lifestyle studies
Alireza Pourrahim,1,*Mohammad Mahdi Pourrahim,2Khadijeh Najafi Ghobadi,3Alireza Vasiee,4
1. Student Research Committee, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran. 2. Student Research Committee, Faculty of Medicine, Ilam University of Medical Sciences, Ilam, Iran. 3. Department of Biostatistics, Faculty of Health, Ilam University of Medical Sciences, Ilam, Iran. 4. Department of Nursing, Faculty of Nursing and Midwifery, Ilam University of Medical Sciences, Ilam, Iran.
Introduction: Pediatric nonalcoholic fatty liver disease (NAFLD) prevalence is rising in parallel with childhood obesity. Mediterranean-style dietary patterns are proposed to reduce hepatic steatosis, inflammation and insulin resistance through high monounsaturated fat, fibre and antioxidant intake. We performed a systematic review of randomized controlled trials (RCTs) and complementary observational evidence to evaluate whether Mediterranean-style interventions prevent progression of pediatric NAFLD.
Methods: A comprehensive literature search was performed in accordance with PRISMA guidelines. The databases searched included PubMed, Embase, Scopus, and Web of Science up to May 2025. The search strategy incorporated a combination of keywords such as: (“Mediterranean diet” OR “Mediterranean-style” OR “olive oil”) AND (“nonalcoholic fatty liver” OR “NAFLD” OR “NASH” OR “fatty liver”) AND (child* OR pediatric*). MeSH/Emtree equivalents were used where available. Eligibility: RCTs of Mediterranean-style dietary interventions (defined a priori as diets emphasizing vegetables/fruit, whole grains, legumes, olive oil, nuts, fish; reduced saturated fat/refined sugars), alone or with structured physical activity, in participants ≤18 years with imaging- or biochemistry-suspected NAFLD; observational cross-sectional/cohort studies reporting diet adherence and NAFLD outcomes were included to provide contextual evidence. Two reviewers independently screened titles/abstracts and full texts, extracted data (population, intervention definition, duration, outcomes: hepatic steatosis [ultrasound/MRI], ALT/AST, insulin resistance, anthropometry), and assessed risk of bias (RoB 2 for RCTs; Newcastle–Ottawa Scale for observational studies). Disagreements resolved by consensus. Planned synthesis: narrative and quantitative synthesis where data homogeneity permitted.
Results: Across the five included studies (two RCTs, total n=104; three cross-sectional studies, total n=475; combined N≈579), the aggregated evidence indicates that Mediterranean-style interventions are associated with short-term improvements in anthropometry, liver enzymes and insulin resistance, but do not show clear superiority to active low-fat comparators over 12 weeks. Quantitatively, RCTs reported mean within-group reductions in ALT of approximately 18–25 U/L and in AST of ≈10–16 U/L, a modest decrease in ultrasonographic steatosis (~0.8% by reported measures), and one trial documented mean weight loss of −5.1 kg; measures of insulin resistance improved in both intervention and control arms. Observational studies consistently found lower adherence to a Mediterranean pattern among children with NAFLD (e.g., mean KIDMED score 2.6±2.4 in NAFLD vs 6.2±1.9 in healthy controls; r=−0.53, p<0.05). Heterogeneity in outcome metrics (biochemical vs ultrasound), short follow-up (median 12 weeks), small sample sizes, and study design differences precluded a pooled meta-analysis; overall risk of bias was moderate and certainty of evidence low.
Conclusion: Available randomized evidence (short, small trials) suggests Mediterranean-style interventions are associated with improvements in liver enzymes, weight and insulin resistance in children with NAFLD; however, they were not clearly superior to low-fat dietary comparators over 12 weeks. Cross-sectional data support an inverse association between Mediterranean diet adherence and NAFLD presence/severity. Certainty of evidence is low to very low due to small sample sizes, short duration, and outcome heterogeneity. Larger, adequately powered RCTs with standardized intervention definitions, longer follow-up and quantitative liver fat (MRI-PDFF) and fibrosis endpoints are required to determine whether Mediterranean dietary approaches can prevent disease progression in pediatric NAFLD.