It's human nature to assume that if one appears slim and is physically active, one must also be healthy.
This is not always the case.
You could be thin on the outside, but still carry a lot of visceral fat on the inside, especially in your liver.
This type of body fat lines your abdominal walls and wraps around many of your internal organs.
Of late, cases of metabolic dysfunction-associated fatty liver disease (MAFLD) have been rising.
Previously known as non-alcoholic fatty liver disease (NAFLD), the condition already affects approximately a quarter of the world’s population, and is becoming a major public health concern.
The name change is because experts felt MAFLD better captures the core issue, i.e. fatty liver linked to metabolic problems such as obesity, diabetes, etc, rather than just “non-alcoholic” causes.
This allows for clearer diagnosis, better patient identification and addressing metabolic risks more directly.
Traditionally associated with excess body weight, the disease is also surging in normal-weight individuals – a condition termed as lean/non-obese MAFLD.
Many Malaysians who appear fit, active or are within the normal body mass index (BMI) frame may unknowingly carry excess fat in the liver, driven by underlying hormonal and metabolic changes, rather than visible weight gain.
While there is no local data for lean MAFLD, according to the 2023 National Health and Morbidity Survey (NHMS), an estimated three in 10 Malaysian adults (28.2%) have MAFLD.
More worrying is that these individuals are, on average, 10 years younger than the global average and present with more concurrent illnesses.
Similar ill health risks
Recent studies also suggest that individuals with lean MAFLD exhibit similar heart- and cancer-related death rates as obese MAFLD individuals, and increased risk of death in general.
Furthermore, lean MAFLD is commonly associated with sarcopenia, a progressive loss of muscle quantity and quality.
The features of lean MAFLD, such as visceral obesity, insulin resistance and metabolic inflammation, are inducers of sarcopenia, whereas loss of muscle mass and function further exacerbates visceral fat accumulation and lean MAFLD.
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Consultant endocrinologist and internal medicine physician Dr Kiran Nair says: “People are getting lean MAFLD due to increasing insulin resistance – some of my patients cannot understand why their sugars are slightly elevated although they are slim and have a normal BMI.
“Initially, we were also stumped, but more emerging evidence shows that genetics play a part, along with how your visceral fat is distributed, lack of muscle, poor sleep, increased stress, etc.”
She adds: “How many people actually measure their body fat percentages?
“Only now, mostly in the urban areas, there are body fat measurement devices, but in the past, there were none.”
Easy measurements
Generally speaking, those with pear-shaped bodies (i.e. fat stored in the hips and thighs) have less dangerous visceral fat than those with apple shapes (i.e. belly fat).
This makes those with pear shapes metabolically healthier, although managing overall fat is still important for joint and metabolic health.
One good marker to gauge your visceral fat is to measure your abdominal or waist circumference.
Those with a waist circumference under 94cm for men and under 80cm for women are unlikely to need to worry about their levels of visceral fat.
However, those with a waist circumference over 102cm for men and over 88cm for women face significantly increased risk for ill health.
But these can vary by ethnicity and other factors, so it’s best to ask a doctor to interpret your results.
A simpler guide is to keep your waist size to less than half your height, known as the waist-to-height ratio.
This can help prevent health conditions like type 2 diabetes, heart disease and high blood pressure.
Says Dr Kiran: “The group mostly affected by lean MAFLD are the 20–40-year-olds, who have easy access to everything.
“They think they are well, but don’t realise that playing pickleball or tennis once or twice a week is not enough.
“Late nights, liquid calories and bad diets are also the culprits.
“As for women, they mostly did aerobic activities in the past, but there’s a bit more awareness on strength training now so, hopefully, we’re on the right path.”
A challenge to diagnose
The liver performs hundreds of vital functions, including filtering toxins and waste from the blood, metabolising nutrients, producing essential proteins, making bile for digestion, storing glucose and vitamins, and fighting infections.
This makes it crucial for metabolism, detoxification, immunity and digestion within the body.
Even healthy livers contain some fat, but if your liver has more than 5% of fat, you may have some form of MAFLD.
If that fat is accompanied by inflammation and liver cell damage, it is called non-alcoholic steatohepatitis (NASH).
If MAFLD progresses to NASH, it can sometimes cause people to experience liver damage similar to that caused by alcohol abuse, even if they do not drink.
From NASH, the disease can potentially lead to liver scarring (fibrosis) and irreversible liver damage (cirrhosis).
“The only non-invasive way to diagnose MAFLD is through a liver ultrasound, but we must first make a distinction between obesity-related MAFLD and lean MAFLD.
“While obesity-related MAFLD patients fit the risk profile (i.e. type 2 diabetes, high blood pressure, abnormal lipid profiles, etc), lean patients do not, so they’re overlooked and harder to manage.
“Fatty liver disease usually doesn’t cause symptoms.
“Patients may complain of tiredness, abdominal discomfort or pain, but these are general symptoms that could be due to something else,” explains consultant gastroenterologist, hepatologist and physician Dr James Emmanuel.
Instead of heading to the doctor’s clinic, patients tend to pass off vague symptoms as stress- or food-induced.
He says: “The amount of fat that is enveloping your organs need not reflect on your body surface area or BMI.
“You can have a normal waist circumference and still have lean MAFLD.
“When we can’t attribute MAFLD to a particular reason, we have to identify secondary causes, e.g. is the patient taking alcohol, oestrogen, steroids or traditional medicine, as these can cause liver damage.”
Often, the blood tests also come back normal.
“Hence, these lean patients can go on for years and years with undiagnosed fatty liver progressing on to fibrosis and then liver cirrhosis, and that’s when we catch them, by which time it is too late.
“With diabetic patients, the doctor will screen them using a Fib-4 index scoring to determine if the patient requires an ultrasound as they have a risk factor for fatty liver. So, they’re screened early,” says Dr James.
He adds: “The lean fellows are asymptomatic so we have to fall back on risk profiling, whether they have a strong family history of MAFLD, diabetes or prediabetes.
“This can trigger a doctor to recommend the patient for a liver ultrasound.
“If you wait for the liver enzymes to go up, they may have progressed to liver fibrosis.
“You could have a perfectly normal liver function result and the only way to detect inflammation in the liver is via a liver biopsy, which we don’t conventionally do.”
At the cirrhosis stage, the only option is a liver transplant.
“The more the risk factors, the faster the progression, though at various levels of weight loss, you can actually reverse fatty liver.
“If you lose 3% of body weight, it actually helps with resolution of fatty liver changes; a 5% weight loss helps with inflammation and ballooning; at 7%, NASH gets resolved, and weight loss of 10% and above, fibrosis regresses.
“This is important as fibrosis is one step before cirrhosis where fatty liver cannot be reversed,” he points out.
Link to insulin resistance
Dr Kiran notes that most lean MAFLD patients have high fasting insulin (serum insulin) levels.
A fasting glucose test tells you the result of the metabolic process (i.e. blood sugar level), while a fasting insulin test tells you the effort your body expends during the process (i.e. hormone response).
High fasting insulin with normal fasting glucose is a key sign of insulin resistance, where cells ignore insulin, forcing the pancreas to produce more to keep blood sugar in check.
“Insulin resistance is what causes fatty liver and is associated with weight gain, causing visceral deposition of fat.
“Asians are thin, but we have a genetic predisposition to insulin resistance.
“People traditionally don’t do fasting insulin tests as it is expensive, but I think it is being recommended more or when the doctor has a high degree of suspicion,” she says.
Another way to monitor your blood glucose levels is to wear a continuous glucose monitor (CGM) device that tracks glucose levels in real-time, 24/7, through a tiny sensor under the skin.
The sensor sends data to a receiver or smartphone app, helping people (especially with diabetes) see trends, get alerts for unusual levels, and make better decisions about food, activity and medicine without constant finger pricks.
Dr Kiran says: “It has become quite trendy and though it is expensive, it roughly gives you an idea and guides you along in managing your glucose levels.”
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Meanwhile, Dr James’ parting advice is: “Do an annual baseline blood test, and if you can afford it, a fasting insulin test, and if any of those are abnormal, get a liver ultrasound done for MAFLD.”
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