World journal of gastroenterologyDec 4, 2014

Links Between Obesity, Fatty Liver Disease, and Gut Bacteria

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 31, 2026

Abstract

Nonalcoholic fatty liver disease (NAFLD) is associated with the increasing prevalence of obesity worldwide.

NAFLD represents a spectrum of liver conditions from simple fat accumulation to cirrhosis.
Both metabolic syndrome and NAFLD are linked to a higher risk of liver cancer.
Changes in the intestinal microbiome may contribute to the development of obesity and NAFLD.
The gut and liver connection via the portal venous system may increase the liver's exposure to harmful bacteria and toxins.
Dysbiosis, or altered gut bacteria, may promote fat accumulation in the liver through various mechanisms, including inflammation and changes in metabolism.
Diet modifications and probiotics could potentially regulate intestinal microbes and address obesity-related health issues.

Simplified

Nonalcoholic fatty liver disease (NAFLD) is a chronic liver disorder that is increasing in prevalence with the worldwide epidemic of obesity. NAFLD is the hepatic manifestation of the metabolic syndrome. The term NAFLD describes a spectrum of liver pathology ranges from simple steatosis to steatosis with inflammation nonalcoholic steatohepatitis and even cirrhosis. Metabolic syndrome and NAFLD also predict hepatocellular carcinoma. Many genetic and environmental factors have been suggested to contribute to the development of obesity and NAFLD, but the exact mechanisms are not known. Intestinal ecosystem contains trillions of microorganisms including bacteria, Archaea, yeasts and viruses. Several studies support the relationship between the intestinal microbial changes and obesity and also its complications, including insulin resistance and NAFLD. Given that the gut and liver are connected by the portal venous system, it makes the liver more vulnerable to translocation of bacteria, bacterial products, endotoxins or secreted cytokines. Altered intestinal microbiota (dysbiosis) may stimulate hepatic fat deposition through several mechanisms: regulation of gut permeability, increasing low-grade inflammation, modulation of dietary choline metabolism, regulation of bile acid metabolism and producing endogenous ethanol. Regulation of intestinal microbial ecosystem by diet modifications or by using probiotics and prebiotics as a treatment for obesity and its complications might be the issue of further investigations.

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Links Between Obesity, Fatty Liver Disease, and Gut Bacteria

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