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Studies conducted by The Chinese University of Hong Kong (CUHK) have revealed that non-alcoholic fatty liver disease (NAFLD) afflicts even the non-obese population. Researchers of the CUHK Faculty of Medicine have conducted two studies on lean NAFLD patients. Findings of the first study showed that 1 out of 5 non-obese subjects from the community suffered from NAFLD, with risk factors such as high blood sugar level. The other study discovered that the severity of the disease is less in non-obese NAFLD patients than in obese patients. Nevertheless, more than 40% of non-obese patients were diagnosed with steatohepatitis while about 30% of them had severe liver fibrosis. CUHK researchers, therefore, recommend that non-obese NAFLD patients with concurrent metabolic diseases should undergo proper assessment for advanced liver diseases.

The first study has been published in the international medical journal, The American Journal of Gastroenterology; the second one in Hepatology.   

Epidemiology of non-obese NAFLD patients is poorly understood

NAFLD is currently the most common chronic liver disease worldwide and affects 27% of the Hong Kong adult population. It is the second leading indication for liver transplantation and the third leading cause of liver cancer in the United States.

Prof. Grace Lai Hung WONG, Professor, Division of Gastroenterology and Hepatology, Department of Medicine and Therapeutics, Faculty of Medicine at CUHK, stated, ‘Though NAFLD rarely shows clinical symptoms, it may progress to steatohepatitis, cirrhosis, and hepatic carcinoma. NAFLD used to be associated with obesity, but it is now found in non-obese people as well. The epidemiology and clinical characteristics of this special group are poorly understood. Physicians are just beginning to learn more about NAFLD in the lean population.’

1 out of 5 non-obese community subjects found with NAFLD

Researchers from the Faculty of Medicine at CUHK conducted two prospective studies from 2006 to 2015. In the first study, 911 citizens were randomly selected from the general population. They underwent magnetic resonance imaging, and had their liver fat and fibrosis measured with a FibroScan machine. Using the Asian definition of obesity (Body Mass Index, BMI, ≥ 25kg/m²), 210 subjects of the study were classified as obese and 701 as non-obese.

Findings showed that 61% of obese subjects suffered from NAFLD. It is worth noting that 19% of the non-obese subjects also suffered from NAFLD. The non-obese NAFLD patients had lower markers of liver injury and fibrosis, suggesting that the severity of their disease was less.  

Moreover, the study findings identified enlarged waist circumference, elevated blood sugar (glycated hemoglobin level), insulin resistance, higher ferritin level, and the presence of polymorphism of the PNPLA3 gene as risk indicators of NAFLD in non-obese patients.

Assessment is recommended for NAFLD patients with concurrent metabolic diseases

CUHK researchers also examined the liver biopsy cohort to further explore the clinical characteristics of NAFLD in non-obese patients. 307 patients who underwent liver biopsy for NAFLD were identified, among whom 235 were obese and 72 were non-obese. Results showed that compared with obese patients, non-obese patients were less susceptible to liver fibrosis. Nonetheless, 44% of these non-obese patients presented with steatohepatitis (NAFLD with active inflammation); 26% with severe liver fibrosis.

Prof. Vincent Wai Sun WONG, Professor, Division of Gastroenterology and Hepatology, Department of Medicine and Therapeutics, Faculty of Medicine at CUHK, concluded, ‘Nearly 20% of the people with BMI2 still have NAFLD. Although non-obese patients tend to have less severe liver disease, they are still prone to developing steatohepatitis and liver fibrosis. Therefore, those with concurrent metabolic diseases should still undergo proper liver assessment.’