Positive Effects of Exercise Intervention without Weight Loss and Dietary Changes in NAFLD-Related Clinical Parameters: A Systematic Review and Meta-Analysis.

Ambrin Farizah Babu,Susanne Csader,Hani El-Nezami,Ursula Schwab,Kati Hanhineva,Johnson Lok,Carlos Gómez-Gallego

doi:10.3390/nu13093135

Abstract

One of the focuses of non-alcoholic fatty liver disease (NAFLD) treatment is exercise. Randomized controlled trials investigating the effects of exercise without dietary changes on NAFLD-related clinical parameters (liver parameters, lipid metabolism, glucose metabolism, gut microbiota, and metabolites) were screened using the PubMed, Scopus, Web of Science, and Cochrane databases on 13 February 2020. Meta-analyses were performed on 10 studies with 316 individuals who had NAFLD across three exercise regimens: aerobic exercise, resistance training, and a combination of both. No studies investigating the role of gut microbiota and exercise in NAFLD were found. A quality assessment via the (RoB)2 tool was conducted and potential publication bias, statistical outliers, and influential cases were identified. Overall, exercise without significant weight loss significantly reduced the intrahepatic lipid (IHL) content (SMD: −0.76, 95% CI: −1.04, −0.48) and concentrations of alanine aminotransaminase (ALT) (SMD: −0.52, 95% CI: −0.90, −0.14), aspartate aminotransaminase (AST) (SMD: −0.68, 95% CI: −1.21, −0.15), low-density lipoprotein cholesterol (SMD: −0.34, 95% CI: −0.66, −0.02), and triglycerides (TG) (SMD: −0.59, 95% CI: −1.16, −0.02). The concentrations of high-density lipoprotein cholesterol, total cholesterol (TC), fasting glucose, fasting insulin, and glycated hemoglobin were non-significantly altered. Aerobic exercise alone significantly reduced IHL, ALT, and AST; resistance training alone significantly reduced TC and TG; a combination of both exercise types significantly reduced IHL. To conclude, exercise overall likely had a beneficial effect on alleviating NAFLD without significant weight loss. The study was registered at PROSPERO: CRD42020221168 and funded by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement no. 813781.

Highlights

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, affecting around 25% of the world’s population [1] and 23% of the European population [2]
One out of the 10 studies had two exercise intervention arms with different exercise regimes—aerobic exercise and resistance training [34]—which were counted as separate randomized clinical trials (RCTs) exercise intervention arms
Each intervention arm was compared with the control arm and divided into its subgroups

Summary

Introduction

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, affecting around 25% of the world’s population [1] and 23% of the European population [2]. It encompasses liver conditions ranging from benign steatosis to non-alcoholic steatohepatitis (NASH), including inflammation with or without fibrosis [3]. The first step to improving NAFLD pathology in its early stages is focused on lifestyle modifications [9] These modifications include increased physical activity and consumption of a healthy diet with restricted intake of saturated fat and controlling body weight and cardiometabolic disorders related to metabolic syndrome [9,10]. A combination of hypocaloric diet and exercise resulted in significant improvements in anthropometric indices, total cholesterol, insulin sensitivity, liver biochemistry, ultrasonography (US) findings of the liver, and physical fitness [11]

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