Dietary Interventions in Patients With Non-alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis

Abstract

Background: With no approved pharmacotherapy to date, the present therapeutic cornerstone for non-alcoholic fatty liver diseases (NAFLD) is a lifestyle intervention. Guidelines endorse weight loss through dietary modifications, physical exercise, or both. However, no consensus exists on the optimal dietary treatment.Objectives: The aim of our systematic review and meta-analysis was to summarize and assess the evidence for applied types of dietary interventions on the liver and metabolic outcomes in patients with NAFLD, aside from any effects of exercise intervention.Methods: This systematic review was conducted according to the Preferred Reporting Items of Systematic Reviews and Meta-analysis (PRISMA) statement guidelines. The search was conducted in PubMed, Scopus, and Cochrane databases in February 2020. Included were only dietary interventions without exercise. This study was registered at PROSPERO: CRD42020203573.Results: Eight randomized controlled trials, seven with endpoint reduction of hepatic steatosis, one with an assessment of endpoint fibrosis, were included in this systematic review, five of which were included in the meta-analysis. Mediterranean dietary interventions without energy restriction (n = 3) showed significant reduction of intrahepatic lipid content (IHL) (SDM: −0.57, 95% CI: −1.04, −0.10), but there was no significant change in alanine transaminase (ALT) (SDM: 0.59, 95% CI: −0.5, −1.68). Hypocaloric dietary interventions with foods high in unsaturated fatty acids (n = 2) led to a significant decrease in ALT (SDM: −1.09, 95% CI: −1.49, −0.69) and aspartate aminotransferase (AST) (SDM: −0.75, 95% CI: −1.27, 0.23); yet effects on steatosis could not be aggregated due to different assessment techniques. Mediterranean diet did not lead to significant changes in concentrations of gamma-glutamyl transpeptidase (γGT), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), fasting glucose or insulin, or homeostatic assessment for insulin resistance.Conclusions: In patients with NAFLD, Mediterranean and hypocaloric dietary interventions favoring unsaturated fatty acids result in improvements in IHL and transaminases. Since many dietary intervention studies are combined with exercise interventions and there is a paucity of ample-sized studies examining dietary interventions on the more advanced and clinically relevant stages of NAFLD, that is active and fibrotic NASH, with multiparametric imaging and liver histology as outcome measures, the optimal dietary invention in NAFLD remains to be defined.

NAFLD and Physical Exercise: Ready, Steady, Go!

“…However, it is important to note that the diet without exercise did not lead to significant changes in liver enzymes, lipid profile, fasting glucose or insulin, or homeostatic assessment for insulin resistance. On the other hand, hypocaloric diet with foods high in unsaturated fatty acids significantly decreases ALT and AST, but its effects on steatosis remain to be established ( 6 ).…”

Lifestyle changes in patients with non-alcoholic fatty liver disease: A systematic review and meta-analysis

“…However, the effect on liver enzymes, importantly differs among studies as some of them only showed differences within the intervention group. A novel systematic review and meta-analysis by Houttu et al [ 90 ] showed that hypocaloric diets reduce ALT levels SMD: −1.09, 95% CI: −1.49, −0.69) as well as AST levels compared to the control group (SMD: −0.75, 95% CI: −1.27, 0.23). Exercise by itself did not reduce liver enzymes, differing from the results showed by Orci et al [ 91 ] (ALT: weighted mean difference [WMD] –3.30 IU/L; 95% CI, –5.57 to –1.04; AST: WMD –4.85 IU/L; 95% CI, –8.68 to –1.02).…”

The Interaction between the Gut Microbiome and Bile Acids in Cardiometabolic Diseases

“…Furthermore, it is one of the leading (and growing) indications for liver transplantations [39]. In recent years, it has been established that diet and the GM play an essential role in the progression of NAFLD [40,41]. Significant advances have been made linking the (gut-derived) metabolome to NAFLD and NASH.…”