Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Nov 14, 2020; 26(42): 6514-6528
Published online Nov 14, 2020. doi: 10.3748/wjg.v26.i42.6514
Nonalcoholic fatty liver disease in lean subjects: Prognosis, outcomes and management
Lampros Chrysavgis, Eleftheria Ztriva, Adonis Protopapas, Konstantinos Tziomalos, Evangelos Cholongitas
Lampros Chrysavgis, Evangelos Cholongitas, First Department of Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, Athens 11527, Greece
Eleftheria Ztriva, Adonis Protopapas, Konstantinos Tziomalos, First Propedeutic Department of Internal Medicine, Medical School, Aristotle University of Thessaloniki, AHEPA Hospital, Thessaloniki 54636, Greece
Author contributions: Chrysavgis L, Ztriva E, Protopapas A, Tziomalos K and Cholongitas E contributed to this paper; Chrysavgis L, Ztriva E, Protopapas A and Tziomalos K wrote the paper; Cholongitas E made critical revisions to the manuscript and final approved the version of the article to be published.
Conflict-of-interest statement: All the authors have no conflict of interest to disclose with respect to this review.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Evangelos Cholongitas, MD, Associate Professor, First Department of Internal Medicine, Medical School, National and Kapodistrian University of Athens, Laiko General Hospital, Agiou Thoma 17, Athens 11527, Greece. cholongitas@yahoo.gr
Received: August 30, 2020
Peer-review started: August 30, 2020
First decision: September 12, 2020
Revised: September 24, 2020
Accepted: October 20, 2020
Article in press: October 20, 2020
Published online: November 14, 2020

Nonalcoholic fatty liver disease (NAFLD) accounts for most cases of chronic liver disease worldwide, with an estimated global prevalence of approximately 25% and ranges from simple steatosis to nonalcoholic steatohepatitis and cirrhosis. NAFLD is strongly connected to metabolic syndrome, and for many years, fatty liver was considered to be an exclusive feature of obese patients. However, recent studies have highlighted the presence of NAFLD in non-obese subjects, with or without increased visceral fat or even in lean subjects without increased waist circumference. “Lean NAFLD” is a relatively new concept and there is significant scientific interest in understanding the differences in pathophysiology, prognosis and management compared with NAFLD in overweight/obese patients. In the present editorial, we discuss the clinical and metabolic profiles and outcomes of lean NAFLD compared with both obese NAFLD and lean healthy individuals from Asian and Western countries. Moreover, we shed light to the challenging topic of management of NAFLD in lean subjects since there are no specific guidelines for this population. Finally, we discuss open questions and issues to be addressed in the future in order to categorize NAFLD patients into lean and non-lean cohorts.

Keywords: Lean nonalcoholic fatty liver disease, Non-obese nonalcoholic fatty liver disease, Clinical outcomes, Metabolic outcomes, Disease management, Lifestyle interventions

Core Tip: Affecting approximately one fourth of the global population, non-alcoholic fatty liver disease (NAFLD) is the predominant cause of chronic liver disease and for many years it was considered as a disease affecting only obese people. However, a significant proportion of non-obese or even lean individuals develop NAFLD. Therefore, it is of great interest to discuss the differences in prognosis, metabolic profiles and outcomes as well as the current management of lean NAFLD patients as compared with both obese NAFLD patients and lean healthy controls.