Why Do Lean People Get Fatty Liver Disease More Often? – Researchers Find Out Why

What is Fatty Liver Disease?

Fatty liver disease is a condition that is characterised by a build-up of fat in the liver, and affects a quarter of the world’s population.

Although it commonly develops in obese and overweight people, many individuals with a body-mass index of less than 25kg/m2 will develop the disease, and they tend to have worse outcomes as compared to obese patients.


Researchers have found out how fatty liver disease develops in lean people, helping the development of potential treatments for these patients.

“Lean fatty liver patients have a very distinct metabolism as compared to non-lean ones, and thise can explain some of the differences we see in disease progression,” according to Jacob George, Professor at the Westmead Institute for Medical Research in Australia.

During the study, researchers compared the gut bacteria, metabolism, and genetic profiles of patients with lean and non-lean fatty liver disease to get to know factors that contribute to disease development and progression.

Compared to non-lean patients, lean patients contain higher levels of bile acids, which play a role in the digestion of fats, and a protein known as fibroblast growth factor 19 (FGF19).

As per the study published in the Journal of Hepatology, FGF19 and Bile acids increase energy expenditure, which can explain why lean individuals with fatty liver disease stay lean.

This suggests that lean patients who have a fatty liver may have an ‘obesity-resistant‘ profile and better adaptation to an excess intake of calories.

Also, according to co-lead researcher Mohammed Eslam, “We also identified changes in novel genes and particular gut bacteria that can influence the development of fatty liver disease in lean patients. For example, we identified that a variant in the gene TM6SF2, previously associated to fatty liver disease, is more common in lean patients“.

Without treatment, fatty liver disease can result in liver cirrhosis liver scarring, and, in severe cases, liver failure.

“The metabolic adaptive mechanisms in lean fatty liver disease tend to be lost in the late stages of the disease. And this could explain why these patients have worse disease outcomes, as compared to their obese counterparts,” according to Eslam.


“Now that we know more about the metabolic processes and profile behind fatty liver disease in lean people, we can work towards more targeted treatments for these patients.”

Professor George concluded, “Our research is now focused on understanding more about the condition, so that we can prevent its progression, and also to develop more personalised treatment regimens.”