[Dangerous Even for Thin Body Types] Why Do You Have “Fatty Liver Despite Being Thin”? Hidden Causes and the Risk of Progression to NASH (Non-Alcoholic Steatohepatitis)

“I’m by no means overweight, but I was pointed out as having a fatty liver during my health checkup… Why?”

Perhaps you are holding similar questions and anxieties?

The belief that “I’m safe because I’m thin” is actually extremely dangerous. In recent years, fatty liver observed in lean individuals has been drawing attention, and it is becoming clear that there are hidden causes behind it that differ from the commonly known fatty liver.

In this blog, a specialist will address your pinpoint question—”Why do I get a fatty liver even though I’m not overweight?”—and explain its causes along with the risks you should be particularly careful of.

“Why Am I Not Overweight?” Hidden Causes of Lean Fatty Liver

The following causes can be considered for those diagnosed with “fatty liver despite being thin”:

1. Extreme Dieting and Unbalanced Eating Habits

Even in lean individuals who appear healthy at first glance, nutritional balance may be significantly disrupted due to extreme calorie restriction, an unbalanced diet, or excessive multitasking while eating. In particular, a lack of protein can cause fat metabolism in the liver to malfunction, or rapid weight loss can place a burden on the liver, temporarily making it easier for fat to accumulate.

2. Lowered Metabolism Due to Lack of Muscle

Even with low body weight, caution is necessary if you are in a state of “hidden obesity” with extremely low muscle mass. Muscle is one of the tissues in the body that consumes the most energy. When muscle mass is low, basal metabolic rate decreases, making it harder for consumed energy to be burned. As a result, it easily accumulates in the liver as fat.

3. Genetic and Constitutional Factors

Even if no major issues are found in your lifestyle habits, some individuals are genetically or constitutionally prone to accumulating fat in the liver. For instance, if insulin resistance (a constitution where insulin works less effectively) is present in the background, blood sugar control becomes difficult, creating a burden on the liver that leads to fat accumulation.

Lean Fatty Liver Requires More Caution for “NASH” Than Obese Fatty Liver!

The idea that “I’m safe because I’m thin” is extremely dangerous, especially regarding the risk of “NASH (Non-Alcoholic Steatohepatitis).”

Contrary to popular belief, an important fact has been pointed out: lean fatty liver is more likely to progress to NASH with inflammation compared to obese fatty liver. NASH is a condition where not only fat, but also inflammation and fibrosis (stiffening of the liver) occur in the liver, carrying the risk of progressing to liver cirrhosis or liver cancer if left untreated.

While fat tends to accumulate diffusely throughout the body in obese types, in lean types, limited fat tends to accumulate concentrically in the liver, which is believed to be one reason it easily triggers inflammation. Reassured by your body shape and overlooking it thinking “I’m probably fine” could lead to liver disease advancing without your knowledge.

Knowing the “Quality” of Your Fatty Liver Is Most Important

That is why it is more important than anything to know the exact “quality” of your fatty liver without being misled by your body shape. Avoid self-judgment and be sure to receive detailed examinations by a specialist.

The following tests are particularly important:

• Ultrasound (Echo) Examination: Visually checks not only the accumulation of fat in the liver, but also the shape and condition of the liver, as well as signs of inflammation.
• Blood Tests: In addition to liver function values (AST, ALT, γ-GTP, etc.), examining special markers that indicate the degree of inflammation and fibrosis (e.g., Type IV Collagen 7S, Hyaluronic Acid, M2BPGi, etc.) allows us to grasp how much damage the liver has sustained.

Our Clinic’s Director Is an Ultrasound Specialist

As an ultrasound specialist, our clinic’s director utilizes years of experience and specialized knowledge to precisely diagnose patients’ liver conditions. Ultrasound examinations are a highly effective, non-invasive means to evaluate the condition and stiffness of liver fat.

If you feel confused or anxious about being diagnosed with “fatty liver despite being thin,” please feel free to consult our clinic. Why not explore the hidden causes and risks of your fatty liver together at our clinic and find the optimal treatment plan?

We also accept online preliminary consultations using Curon. Please feel free to make use of it.