Episode Details

Episode 172: NAFLD and Obesity

Future Dr. Nguyen explains the pathophysiology of non-alcoholic fatty liver disease and how it relates to obesity. Dr. Arreaza gives information about screening and diagnosis of NAFLD. 

Written by Ryan Nguyen, MS4, Ross University School of Medicine. Comments by Hector Arreaza, MD.

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Introduction/Pathophysiology
Nonalcoholic fatty liver disease (NAFLD) refers to the buildup of excess fat in liver cells, occurring without the influence of alcohol or drugs. Nonalcoholic steatohepatitis (NASH) represents a more severe form of NAFLD, characterized by inflammation and liver cell injury due to fat accumulation. If left untreated, NASH can progress to liver fibrosis or cirrhosis. Typically, NAFLD/NASH is diagnosed after other liver conditions are ruled out, making it a diagnosis of exclusion.

NAFLD -> NASH -> Cirrhosis -> Liver failure. Another term for NAFLD is metabolic dysfunction-associated steatotic liver disease. 

Fatty liver disease is identified when more than 5% of liver weight consists of fat, whereas, NASH is diagnosed when this fat accumulation is accompanied by inflammation and liver cell injury, sometimes leading to fibrosis. Understanding these distinctions is crucial in recognizing and managing the spectrum of liver conditions associated with obesity and metabolic syndrome.

BMI serves as a tool to gauge body fat levels: individuals are categorized as normal weight if their BMI falls between 18.5 and 24.9, overweight if it ranges from 25 to 29.9. Class I obesity is diagnosed with a BMI of 30 to 34.9, class II obesity between 35 and 39.9, and class III obesity when BMI exceeds 40.

Obesity puts you at risk of NAFLD, but you can also see NAFLD in non-obese patients, but the prevalence is very low, about 5%. What did you learn about the demographics of NAFLD?

NAFLD is most widespread in regions like South Asia, the Middle East, Mexico, Central and South America, with prevalence rates exceeding 30%. In the United States, prevalence varies with approximately 23-27%, notably higher among Asians at 30%, followed by Hispanic individuals at 21%, White individuals at 12.5%, and Black individuals at 11.6%. 

Across all racial groups, obesity plays a significant role, affecting more than two-thirds of individuals diagnosed with NAFLD. Understanding these demographics underscores the global impact of obesity on NAFLD prevalence.

Diagnosis: Screening/Labs/Imaging/Tools

The American Association for the Study of Liver Diseases does not recommend screening for NAFLD, but if it is discovered an appropriate workup is warranted. 

AST/ALT Ratio

Liver health can be assessed by a series of tests aimed at assessing fat accumulation, inflammation, and fibrosis. Initial screening often includes laboratory tests such as measuring the ratio between aspartate transaminase (AST) and alanine transaminase (ALT), where a ratio less than 1 may suggest possible NAFLD, although it is not diagnostic on its own. Normally, AST is slightly more elevated than ALT. So, if the AST/ALT ratio is lower, then means that ALT is higher than AST. 

FibroSure®.

Additionally, you can measure indirect markers of fibrosis with tests such as FibroSure or FibroTest blood tests that combine several biomarkers including age, sex, gamma-glutamyl-transferase (GGT), total bilirubin, alpha-2-macroglobulin, apolipoprotein A1, haptoglobin, and ALT to provide insights into liver h