Use of the Term Lean for Nonalcoholic Fatty Liver Disease in Individuals With Low Body Mass Index Reply

Although I applaud the American Gastroenterological Association for a clinically pragmatic and relevant practice update on nonalcoholic fatty liver disease (NAFLD) in those with low body mass index (BMI), it brings up concerns with semantic discordance by using the term “lean.”1Long M.T. et al.Gastroenterology. 2022; 163: 764-774.e1Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar The authors appropriately note that NAFLD is generally “associated” with obesity and increased in the presence of other obesity- (or adiposity-) based metabolic complications but remains very “BMI-centric” in citing data supporting the risk for those who have a BMI within the ethnic-specific cutoff of 25 kg/m2 BMI in white and 23 kg/m2 in Asian subjects. Obesity is a multicausal chronic disease with variable clinical phenotypes defined by abnormal or excessive adiposity due to an enduring positive energy imbalance from complex neuroendocrine and behavioral dysregulation of the body’s adipose “set point” that impairs health, including NAFLD, regardless of BMI.2Bray G.A. et al.Obes Rev. 2017; 18: 715-723Crossref PubMed Scopus (631) Google Scholar BMI certainly has been used as a surrogate of adiposity to diagnose and classify obesity because of a very good correlation with population-based adiposity data but has significant limitations for diagnosing individuals with obesity because of heterogeneously variable adipose distribution (including ectopic hepatic fat) and muscularity or sarcopenia in addition to fluid status, edema, age, and sex. The American Association of Clinical Endocrinology recommends screening for and classification of obesity using individualized clinical interpretation of BMI aided by other anthropometric measures such as waist circumference to refine the risk abnormally distributed adiposity or other body composition technologies if needed to confirm excess adiposity.3Garvey W.T. et al.Endocr Pract. 2016; 22: 1-203Abstract Full Text Full Text PDF PubMed Scopus (765) Google Scholar For example, using waist circumference to more accurately refine an individual’s obesity-related cardiometabolic risk includes NAFLD regardless of BMI.4Lee J.H. et al.Nutrients. 2022; 14: 2994Crossref PubMed Scopus (2) Google Scholar To this point, the American Association of Clinical Endocrinology followed up with a position statement proposing a new diagnostic term, “adiposity-based chronic disease,” to better align with the true pathophysiology of obesity and adiposity-based complications such as NAFLD.5Mechanick J.I. et al.Endocr Pract. 2017; 23: 372-378Abstract Full Text Full Text PDF PubMed Scopus (153) Google Scholar This concept was integrated into the recent American Association of Clinical Endocrinology clinical practice guideline on the diagnosis and management of NAFLD.6Cusi K. et al.Endocr Pract. 2022; 28: 528-562Abstract Full Text Full Text PDF PubMed Google Scholar The term “lean” in the context of animals is defined by having little fat or adipose tissue but may also include “lacking or deficient in flesh” (https://www.merriam-webster.com/dictionary/lean); however, the former is much more colloquially relevant. Clinically important to note is that despite the American Gastroenterological Association practice update using the term “lean,” it appropriately advises a 3%–5% target for weight loss plus nutritional optimization and exercise because NAFLD is truly an adiposity-based disease as long as other etiologies are ruled out that cause fatty liver in truly lean individuals. To this end, I suggest healthcare professionals adopt improved nomenclature for these situations such as “sarcopenic obesity” using classification criteria per the European Association for the Study of Obesity/European Society for Clinical Nutrition and Metabolism critical appraisal categorized by BMI < 25 kg/m2 (<23 kg/ m2 for Asian ethnicity).7Donini L.M. et al.Clin Nutr. 2020; 39: 2368-2388Abstract Full Text Full Text PDF PubMed Scopus (148) Google Scholar AGA Clinical Practice Update: Diagnosis and Management of Nonalcoholic Fatty Liver Disease in Lean Individuals: Expert ReviewGastroenterologyVol. 163Issue 3PreviewNonalcoholic fatty liver disease (NAFLD) is well recognized as a leading etiology for chronic liver disease, affecting >25% of the US and global populations. Up to 1 in 4 individuals with NAFLD have nonalcoholic steatohepatitis, which is associated with significant morbidity and mortality due to complications of liver cirrhosis, hepatic decompensation, and hepatocellular carcinoma. Although NAFLD is observed predominantly in persons with obesity and/or type 2 diabetes mellitus, an estimated 7%–20% of individuals with NAFLD have lean body habitus. Full-Text PDF ReplyGastroenterologyVol. 164Issue 3PreviewWe thank Dr Nadolsky1 for the interest in our article on the diagnosis and management of nonalcoholic fatty liver disease (NAFLD) in lean individuals.2 We agree that the standard definition of “lean NAFLD” based on body mass index has significant limitations. Body mass index, as a measure of general adiposity, does not allow a description of individual fat depots, including visceral fat, which more strongly associates with central adiposity, as measured by waist circumference. At present, in the United States, waist circumference is not routinely measured in clinical practice, so clinicians often do not have this important information available when making clinical recommendations to patients. Full-Text PDF