Fatty liver disease with a lean BMI may mean higher risk of heart disease

Researchers warn doctors not to overlook lean patients with non-alcoholic fatty liver disease because they could be facing serious health issues.

Chris Arnold 3 minute read May 27, 2022
Liver with internal organs

Non-alcoholic fatty liver disease occurs when a person consumes more fat and sugars than their body can process and store. GETTY

People with what is considered to be a lean body mass index (BMI) but who have non-alcoholic fatty liver disease (NAFLD) are more likely to also have cardiovascular disease when compared to people living with obesity, according to a new study.

Almost 1.5 million people in Canada are living with NAFLD, according to the Canadian Liver Foundation, a condition that acts as a sort of umbrella term for various liver conditions that impact people who either don’t drink or drink very little. 

The condition usually has no symptoms, making it difficult to actually diagnose, but it can lead to other dangerous ailments including diabetes, cardiovascular disease and cirrhosis or scarring of the liver. 

“Our team had expected to see that those with a normal BMI would have a lower prevalence of any metabolic or cardiovascular conditions, so we were very surprised to find this link to cardiovascular disease,” Karn Wijarnpreecha, lead researcher of the study said in a news release. “Too often, we overlook NAFLD patients with a normal BMI because we assume their risk for more serious conditions is lower than those who are overweight. But this way of thinking may be putting these patients at risk.” 

Leaner people had more brain and cardiovascular disease

In a study of more than 10,000 adults with NAFLD between 2012 and 2021, researchers compared the occurrence of various co-morbid conditions among four weight classes: lean, which consisted of a BMI between 18.5 and 24.9, overweight was 25 to 29.9, class 1 obesity was 30 to 24.9, and class 2-3 obesity was 35 to more than 40.

Lean participants had fewer instances of conditions such as cirrhosis, diabetes mellitus, hypertension, and dyslipidemia, when compared to non-lean participants. However, the same lean patients were found to have more occurrences of peripheral vascular disease, cerebrovascular (brain) disease and cardiovascular disease. 

“In further analysis, we found that lean patients with NAFLD also had a significantly higher prevalence of cardiovascular disease, independent of age, sex, race, smoking status, diabetes, hypertension, and dyslipidemia,” Wijarnpreecha said.

Researchers aren’t exactly sure why lean patients are more susceptible to some conditions than others, but encourage doctors to not overlook NAFLD patients with lower BMI as they could be facing serious health issues. Additional research and studies are planned that will follow the patients long-term to determine if lean patients have a higher risk of developing cardiovascular issues as a result of NAFLD. 

The scientists shared their research as part of Digestive Disease Week 2022, a conference in San Diego. 

A BMI, or body mass index, is a general measurement of someone’s weight relative to their height. To find a BMI, a person divides the weight in kilograms by the height in metres squared. As an example, if a person weighs 69 kilograms, and is 1.65 metres tall, the BMI is 24.98. BMI does not account for a difference in weight between fat and muscle, however, so an extremely muscular person could have a higher BMI. 

NAFLD occurs when a person consumes more fat and sugars than their body can process and store, according to the Canadian Liver Foundation. The site also acknowledges that obesity is one of the most common causes of NAFLD, and that nearly 30 per cent of Canadian adults — approximately 7.3 million people — are classified as overweight or living with obesity. 


Chris Arnold is a Toronto-based writer.
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