Fatty Liver Is Not Just a Heavy Person’s Problem

There is a widespread belief in Filipino households that fatty liver disease happens to people who are overweight or who drink too much. Neither assumption is entirely true. A growing body of clinical evidence shows that people with normal body weight can develop significant fat deposits in the liver, a condition researchers now call lean non-alcoholic fatty liver disease, or lean NAFLD. In the Philippines, where about 11.9 percent of Filipino NAFLD patients were classified as having lean NAFLD, this is not a rare edge case. It is a documented and underdiagnosed public health concern.

The Disease Has a New Name, but the Risk Is the Same

Medical nomenclature for this condition has evolved rapidly. The global liver disease community agreed in 2023 that non-alcoholic fatty liver disease would now be called metabolic dysfunction-associated steatotic liver disease, or MASLD. The older terms NAFLD and MAFLD remain in wide use in clinical literature, and most Philippine studies still use NAFLD. For the purposes of this article, all three terms refer to the same spectrum of disease.

NAFLD encompasses a disease spectrum ranging in severity from simple steatosis to non-alcoholic steatohepatitis, or NASH, and cirrhosis. An estimated 25 percent of NASH patients may develop cirrhosis, and 10 percent will develop decompensated liver disease. What was once considered a condition exclusive to people with obesity is now confirmed to affect people at any weight.

How Common Is This in the Philippines

In the Philippines, 10 to 20 percent of the population is estimated to have NAFLD. The country’s prevalence mirrors global trends, though national-level data specifically on lean NAFLD remains limited.

A study conducted across two outpatient hepatology clinics from 2007 to 2017 examined 663 Filipino NAFLD patients diagnosed by ultrasound. Most patients in that study were non-lean, accounting for 88.1 percent of the total. But cirrhosis or hepatocellular carcinoma was already present in 8.4 percent of patients at their very first consultation. This means that by the time many Filipinos seek liver care, the disease has already progressed to a serious stage.

A separate Philippine General Hospital study covering 1999 to 2004 found a NAFLD prevalence of 12.2 percent among patients at that institution, with a mean patient age of 42.2 years and a higher proportion of female patients. These are not elderly, visibly unwell patients. They are middle-aged adults who would appear healthy to most observers.

Why Normal BMI Does Not Mean a Healthy Liver

Body mass index, or BMI, is a rough measurement. It captures total weight relative to height but says nothing about where fat is stored in the body. This distinction is critical for understanding lean NAFLD.

In Asians and Pacific Islanders, a BMI below 23 kg per square meter is the threshold for lean classification, because visceral adiposity and metabolic risk develop at a lower BMI in these populations than in Europeans. A Filipino adult with a BMI of 22 may still carry dangerous amounts of fat around internal organs, a condition known as visceral obesity, even while appearing slim.

Visceral adiposity is more strongly implicated in the development of NAFLD regardless of BMI. Nearly a third of lean individuals are likely to be metabolically unhealthy, even when their BMI falls within the normal range.

BMI fails to capture subtle alterations in the amount or distribution of fat that occur in lean NAFLD, making it a suboptimal marker of adiposity in this setting. A person can remain within a normal BMI range while accumulating enough abdominal fat to damage the liver.

Who Is at Highest Risk Among Normal-Weight People

Lean NAFLD does not arise randomly. Research identifies several consistent risk factors that apply even in the absence of excess body weight.

• Genetic predisposition. Lean NAFLD is characterized by significant genetic determinants, including variants of PNPLA3, TM6SF2, and MBOAT7, in individuals with normal BMI. These gene variants affect how the body processes and stores fat in liver cells, independent of overall body weight.
• Insulin resistance and metabolic dysfunction. Although lean NAFLD patients are normal weight, they are often regarded as metabolically obese, as they appear to have some degree of insulin resistance, particularly at the level of adipose tissue. The liver responds to this metabolic signal by accumulating fat, regardless of what the scale says.
• Diet high in fructose and refined carbohydrates. Risk factors for lean NAFLD include high fructose and cholesterol dietary intake, as well as alterations in the gut microbiome. The Filipino diet, which is characteristically high in white rice, sweetened beverages, processed snacks, and fried foods, creates conditions favorable to lean NAFLD development, particularly when physical activity is low.
• Recent weight gain within a normal range. There is increased risk of NAFLD in individuals gaining weight despite remaining within the normal BMI range, or in those who were previously obese and have since returned to normal weight but retain accumulated abdominal fat.
• Sarcopenia. The association between sarcopenia and NAFLD appears in both obese and non-obese NAFLD populations. When NAFLD is combined with sarcopenia, the risk of cardiovascular disease increases regardless of obesity. Sarcopenia, the loss of muscle mass and quality, is increasingly common among sedentary Filipino adults, including those who appear thin.
• Gut dysbiosis. Gut dysbiosis and modified bile acid metabolism further define the pathophysiology of lean NAFLD. Disruptions in the gut microbiome affect how the liver metabolizes dietary fat and can accelerate fat deposition in liver cells.

The Disease Is Silent and Easily Missed

Lean NAFLD is especially dangerous precisely because it produces no obvious physical warning signs. There is no pain, no jaundice in early stages, and no weight change to prompt concern. Most cases are discovered incidentally, often during an ultrasound done for another purpose, or through abnormal findings on a routine blood chemistry panel.

A study on Filipino wellness patients at Makati Medical Center found that elevated liver enzymes, specifically ALT and AST, as well as elevated triglycerides and fasting blood sugar, were associated with ultrasound-detected fatty liver grade. These are laboratory markers that appear during routine annual checkups, yet many patients and even some clinicians fail to connect them to liver disease when the patient is of normal weight.

Clinical guidance from the American Gastroenterological Association specifies that NAFLD should be considered in lean individuals who have metabolic conditions such as type 2 diabetes, dyslipidemia, or hypertension, or who show elevated liver enzymes on blood tests. In the Philippines, where annual executive checkups are common among employed adults in urban centers, these markers are frequently present but not always acted upon.

The Outcomes Are Comparable to Obesity-Related Fatty Liver

A critical finding from recent research challenges the assumption that lean NAFLD is a milder form of the disease.

Despite a better metabolic profile overall, the risk of disease progression to hepatic inflammation, fibrosis, and decompensated cirrhosis in lean individuals is similar to that in obesity-related NAFLD. Lean individuals may in fact experience more severe hepatic consequences and higher mortality relative to those with a higher BMI.

Lean NAFLD individuals with metabolically unhealthy profiles have a higher risk for cardiovascular disease than obese NAFLD individuals. This is a counterintuitive finding with significant implications. A normal-weight Filipino with lean NAFLD and metabolic dysfunction may face higher cardiovascular mortality than a heavier counterpart whose metabolic markers are well controlled.

How Lean NAFLD Is Diagnosed

Diagnosis requires clinical suspicion, which is the first barrier. A physician must consider the possibility in a patient who does not look sick and is not overweight.

Abdominal ultrasound is the most accessible first-line tool for detecting liver fat in the Philippines. It is non-invasive, widely available in public and private hospitals, and capable of detecting moderate to severe steatosis. Blood tests showing elevated ALT, AST, or triglycerides add further grounds for investigation.

Clinical guidance recommends that lean individuals with NAFLD be risk-stratified for hepatic fibrosis to identify those with advanced fibrosis or cirrhosis, and that screening be considered for lean individuals over 40 years of age with type 2 diabetes. Liver biopsy remains the definitive diagnostic method for assessing the degree of inflammation and fibrosis, though it is not a first-line test.

What Can Be Done

There is no approved pharmaceutical drug specifically indicated for lean NAFLD as of 2024. The primary treatment is lifestyle intervention, and even small changes have been shown to be clinically meaningful.

In lean patients with NAFLD, lifestyle intervention, including exercise, diet modification, and avoidance of fructose and sugar-sweetened drinks, targeting a modest weight loss of 3 to 5 percent, is the recommended approach. For a Filipino adult weighing 55 kilograms, that represents a loss of less than 3 kilograms. The goal is not dramatic weight loss but the specific reduction of visceral and liver fat.

Weight reduction has been shown to improve the histology of lean patients with NAFLD. The reduction does not have to be very high. A loss of 5 percent or less can make a measurable histologic difference.

Vitamin E may be considered in lean individuals with biopsy-confirmed NASH who do not have type 2 diabetes or cirrhosis. Oral pioglitazone may also be considered in lean individuals with biopsy-confirmed NASH without cirrhosis. These are secondary options managed by a physician and should not be self-prescribed.

Surveillance for liver cancer through ultrasound and serum alpha-fetoprotein testing, done twice yearly, is recommended for lean NAFLD patients who already have clinical markers of cirrhosis.

The APMARGIN Perspective

Lean NAFLD challenges one of the most deeply held assumptions about liver disease in the Philippines, which is that it is a condition visible on the body. It is not. A person can be slim, active-looking, and metabolically ill at the same time.

This matters for public health policy in at least three ways. First, screening programs and public awareness campaigns that target only overweight or obese Filipinos will miss a documented subset of patients who are at equal or greater risk of progression to cirrhosis and liver cancer. Second, the Filipino dietary pattern, heavy in refined carbohydrates, sugar-sweetened drinks, and processed food, is a modifiable driver of lean NAFLD that deserves targeted nutritional guidance beyond the typical obesity-focused messaging. Third, annual health checkups that generate elevated liver enzyme results must be followed through with clinical investigation, regardless of the patient’s body weight.

The liver does not send early distress signals. The healthcare system, providers, and patients themselves must be better equipped to look for problems that the body does not announce.

Sources

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• Navarroza, E., et al. Clinical and biochemical profiles of lean vs. non-lean NAFLD patients in two Philippine hepatology clinics. Indian Journal of Gastroenterology, 2021. doi:10.1007/s12664-021-01184-6.
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