Updated June 2024

Background

This post was originally prompted by a blog reader who was concerned about her 10-year-old son developing fatty liver. I’ve updated it further after a viral instagram post here where I highlighted the case of a 20 year old who developed fatty liver with almost daily consumption of milk tea boba, and also displayed my own continuous glucose monitor results after directly drinking a milk tea boba to make the point.

During medical training I learned about fatty liver occurring in alcoholics. Chronic intake of alcohol impairs the ability of a healthy liver to break down and release fat, leading to fat deposition inside the liver (more on this in a moment).

Fast forward to my practice today and although I don’t have a large percent of alcoholics in my Silicon Valley practice, I still see an alarming amount of Non-alcoholic Fatty Liver Disease (aka NAFLD), mostly secondary to the process of insulin resistance, a key focus of my work. Like the name indicates, this form of fatty liver is being seen in individuals who have never even touched alcohol or drink very little.

The estimated global prevalence of NAFLD among adults is 38% and is higher in males (40%) vs females (26%) as per this study.

The prevalence is highest in the regions of South Asia (India, Pakistan, Bangladesh, etc.), Southeast Asia, and also parts of East Asia such as mainland China. Mexican and Native Americans are also very high risk for fatty liver. Essentially any region of the world where modernization  and especially westernization of lifestyle and diet has occurred, appears to have a high prevalence of fatty liver.

In response to my instagram post on milk tea boba and fatty liver, there were several comments from individuals from East Asia who believed fatty liver was a problem in Americans only. I highlighted how in countries like Taiwan, the birthplace of mile tea boba, some studies indicate fatty liver is present in up to 40% of the population.

East Asians and South Asians, even with a seemingly slender body habitus, are not immune, and actually appear to be even more susceptible to fatty liver.

What’s especially of concern is that we are seeing NAFLD not only in adults, but also in children and teens. We’ll discuss kids and teens towards the end of the post.

What Causes NAFLD (Non-alcoholic Fatty Liver Disease)?

As mentioned above, it’s insulin resistance that is the most common root cause for NAFLD, and if you’re not familiar with the concept be sure to read this post and refer to my book. By the way, although NAFLD is the commonly recognized acronym for non-alcoholic fatty liver, that recently got changed to MASLD, which stands for Metabolic Dysfunction Associated Steatotic Liver Disease. Until this becomes a mainstream term, I’m going to use NAFLD for now or just say “fatty liver,” as a shortcut to represent non-alcoholic fatty liver in this blog post.

Fatty liver is a complex process, so I’m going to simplify it here and use the animation below to help further illustrate this. Our body has limited storage space in our muscles and liver to store carbohydrates like sugar and starchy foods. We call the storage form of carbohydrates “glycogen.” Think of the glucose molecules from sugar and starches as being cars and the available space in your muscles and liver as being a parking lot that stores the glucose in a form called “glycogen.”

When we consume so much glucose through our diet that it exceeds our liver’s capacity to store glucose as glycogen, the liver ends up having to flip a switch to convert the overflow glucose into fat.  The fancy word for this is “de novo lipogenesis” or DNL, which simply means making new fat out of excess glucose.

Watch the 20 second video below which illustrates this process.

Notice how the red glucose car can’t find parking inside the liver because the liver is full of glycogen (watch the video again if this concept is not clear).  The glucose car’s only option is to enter a “fat machine” and get converted to fat (represented by the big yellow bus), which accumulates inside the liver, turning it into a fatty liver.

Keep in mind that the excess glucose stored need not come from sugar and sweets.  Many of my Indian and Asian patients have fatty livers fueled by excess rice, noodles, bread, sugar-sweetened beverages, and even what they consider “healthy carbs” like quinoa, whole wheat bread, and whole grain cereals.

It’s important for you to understand that although dietary fat can contribute to fatty liver, it’s an abundance of added sugar and excessive carbohydrate consumption that appears to drive most of the nutritional burden of fatty liver disease. 

The word “fatty liver” becomes misleading since it makes people prioritize the removal of dietary fat and instead the addition of low fat foods which often are an abundant source of glucose and even processed fructose, which when consumed on a frequent basis, can fuel fatty liver.

Highlighting Sugar-Sweetened Beverages (SSBs)

As I mentioned earlier, it’s the abundance of carbohydrates, even healthier ones that can overwhelm the liver and get turned into fat. Eating or drinking carbohydrates in excess can have this effect since many of my patients with fatty liver don’t drink sugar sweetened beverages, which I’ll abbreviate as SSBs. Although I highlighted milk tea bobas in my instagram post, below is a more comprehensive list:

  • Iced coffee drinks like Starbuck’s frappuccinos
  • Sweetened milk tea drinks like milk tea boba
  • Fruit smoothies, especially store bought, but even homemade can be a big sugar load
  • Fruit juices like the juice boxes and packets consumed by young kids from an early age
  • Milk shakes
  • Indian sweetened yogurt drinks like mango lassis (the mango syrup used typically has fructose syrup)
  • Sodas and other fizzy fruit flavored drinks
  • Sports and energy drinks with added sugar

Why are SSBs a major dietary culprit? Unlike food you chew on and slowly digest, which causes a slower rise in blood glucose, a liquid beverage contains a much higher dose of glucose in concentrated form, and causes a faster spike in blood glucose (and insulin) since it is already what I call “pre-digested.”

A typical SSB might have 60 grams of sugar (15 teaspoons or 15 sugar cubes) or more, which is like eating 7-8 Reese’s peanut butter cups, but again, the act of drinking the sugar might have even more additional adverse effects because of the velocity of the glucose spike and the crash that follows.

Another problem with many of the listed SSBs are the additional ingredients added to the drinks. Sugar-sweetened iced coffee and milk tea drinks often have fat added to them in the form of cream and syrups that are further concentrated sugar and/or high fructose corn syrup (HFCS). Processed fructose in syrup form (not natural fructose from eating fruit) has been shown to trigger fat production (aka lipogenesis) in the liver. The starchy boba balls in milk tea boba are another source of glucose, which when combined with the added sugar, can cause a cumulative glucose spike.

For milk tea boba, don’t get fooled by 50% or even 0% sugar. Many current and former boba store employees commented in the instagram post that the boba is cooked in black sugar syrup, so you can still get a significant glucose spike from drinking a reduced or even 0% sugar boba.

Most of the venues that serve up these drinks like coffee and milk tea shops also sell sweet treats (pastries, muffins, etc.) and fatty snacks (popcorn fried chicken, etc.), so the combination of SSBs with additional fatty and sugary foods makes the problem worse.

Some parents become defensive when I call out SSBs and say, “an occasional SSB isn’t a problem.” I agree with that statement, if it truly were occasional.

They don’t realize that many teens and young adults might be studying frequently at Starbuck’s where they get an SSB possibly with a sugary snack and then might hit a milk tea shop a few times during the week, in addition to consuming sodas, energy drinks, etc.

The cumulative load of SSBs in a given week is far higher than they estimate which is why we’re seeing fatty liver in even young kids. If you have any doubt about the role of starches in producing fatty liver, just read about how the French delicacy foie gras is made.  Foie gras, which is fatty duck or goose liver, is made from the cruel process of force-feeding these birds a high fat corn mash containing glucose mixed with fat, force fed through a tube called a gavage.

Foie gras producers leverage all the principles we talked about to produce fatty liver disease in ducks at scale. They introduce liquefied sugar and fat into a duck’s mouth through a tube, which is not much different than the liquefied sugar and fat in SSBs introduced through a straw. The duck is typically force fed over a period of 12-15 days. In humans, having SSBs on a frequent basis can lead to similar changes in the liver, but usually over a longer time period. Occasional SSBs are unlikely a problem, but consistent intake, especially in the context of an unhealthy diet and sedentary lifestyle, is a risk.

Diagnosing NAFLD

Imaging

One critical point you need to understand is NAFLD is a silent disease.

Most people do NOT get abdominal pain or any warning symptoms until their liver starts to fail in the more advanced stages.

That’s why my patients are often shocked to discover they have fatty liver. An ultrasound is the most common and accessible imaging study to detect fatty liver. The problem with the ultrasound is your liver needs to be filled with about 30% fat before it shows up on ultrasound, so you might have early stage fatty liver long before it shows up on ultrasound. The more sensitive tests like an MRI-PDFF scan are more costly and not readily available. A fibroscan is used to monitor liver fibrosis or stiffness and fat content in individuals with known fatty liver disease. 

Blood Tests

1. Liver Tests: The AST and ALT blood tests are known as transaminases, which are markers of liver inflammation. These also can be normal in the earlier stages of fatty liver. So you might have a normal ultrasound and normal AST and ALT blood test, but still have early fatty liver. If you want to be proactive in preventing fatty liver disease, don’t wait for these tests to become abnormal

2. Cholesterol Panel: In addition to liver tests, I would also pay attention to your cholesterol panel, specifically the triglyceride levels. Studies show that between 50-75% of individuals with high triglycerides have fatty liver. There’s also a ratio I’ve highlighted in my book and prior blog posts called the triglyceride-to-HDL ratio. Simply take your triglyceride level and divide it by your HDL level and the ratio should be less than 3.0. If your ratio is above 3.5 and especially above 4.0, your risk of fatty liver and overall insulin resistance goes up. Get your ratio as far below 3.0 as you can. This marker usually becomes abnormal before the liver tests do so if you really want to get ahead of fatty liver, monitor this metric and keep it in check

3. Blood Glucose: Consistently elevated blood glucose is a marker of insulin resistance and fatty liver risk. I say consistent, rather than a single fasting blood glucose level that’s high. I would favor using the glucose A1C test which is your average glucose for the past 2-3 months, and also consider trying a continuous glucose monitor (aka CGM) which will give you more real-time data. However, if your fasting blood glucose is high on more than one occasion, that can be an early signal as well.

Body Metrics

Extra inches around the waist might be a sign of excess visceral fat which you can learn about in this post. If you are using weight or body mass index (aka BMI) as a marker, keep in mind that the Asian adjusted cutoff for abnormal BMI is 23 vs 25 for non-Asians. The waist circumference cutoff is also lower for Asians and both these Asian-adjusted cutoffs are part of the diagnostic criteria for NAFLD (MASLD) which you’ll find in the flowchart here put out by the AASLD (American Association for the Study of Liver Diseases). These ethnic cutoffs were created by the WHO (World Health Organization) to recognize how Asians are at risk for insulin resistant conditions like fatty liver at a lower body weight and lower waist circumference.

The good news about the above labs (AST, ALT, lipid panel, A1C, fasting glucose) and the ultrasound is that they are cheap, covered by insurance, and easily accessible for most. You can also track your waist circumference and body weight on your own for free. Continuous glucose monitors (CGMs) are also becoming more affordable, more widely covered by insurance, and as of the updated writing of this blog post, the FDA approved them for over-the-counter use in the US.

Summarizing Risks for NAFLD

Insulin resistance is not just a major cause for NAFLD, it’s also the underlying mechanism for type 2 diabetes, heart disease and common cholesterol issues like high triglycerides and low HDL (healthy cholesterol). Let’s list off some of the typical risks and some of these reiterate the abnormal tests I just mentioned. The more risk factors you have, the greater the chance you have fatty liver.

  1. Excess weight, especially around the waist.
  2. Abnormal blood glucose
  3. Abnormal cholesterol, especially high triglycerides
  4. Metabolic syndrome: this is a condition that represents many of the above risks in combination.  Read about it here.
  5. Ethnicity: South Asians, East Asians, Filipinos, Hispanic/Latinos, and Pacific Islanders are examples of some high risk groups
  6. Diet: A diet high in processed foods (especially fructose and sugar), excess carbohydrates, and the combination of a sugar/starch heavy diet with unhealthy and excess fats
  7. Inactivity: A lack of physical activity in combination with a poor diet is a cumulative risk for fatty liver.

If NAFLD is not reversed and is allowed to progress, the consequences can be liver failure requiring the need for a liver transplant. NAFLD also significantly increases the risk of liver cancer from 1.5 to 15 fold, depending on the study.

Why is NAFLD and Your Liver Important?

I think the liver’s role in optimal health is too often overlooked, especially when it comes to diabetes and blood glucose control. If you want to learn more about the liver’s role in metabolism, listen to my podcast episode here. No matter how much we try to optimize insulin and prevent or reverse insulin resistance, if your liver is not working properly, then glucose control will not be optimal.  The liver is a primary organ for filtering toxins and any amount of excess fat in the liver will clog your filter.

Unless you live in an area of the world untouched by modern civilization, you are being exposed to multiple toxins daily through the food you eat, the air you breathe, the water you drink and even the endless products and cosmetics that come in contact with our skin.  

In today’s industrialized world, we depend on a highly functioning liver filter more than ever to prevent chronic diseases like fatty liver, diabetes, heart disease, cancer, and more. 

A fat-clogged liver filter means your liver cannot effectively remove toxins, so they accumulate in your blood stream which causes more inflammation in the body.  A clogged liver also cannot properly metabolize glucose or lipids.  So this means you may have some combination of inflammation, elevated blood glucose and abnormal cholesterol.  In other words a set-up for diabetes, heart disease, cancer, autoimmune disease, neurodegenerative conditions like Alzheimer’s disease, and more.

Many of my female patients who struggle to lose weight despite diet and exercise often have a clogged liver filter leading to more toxins in their blood stream.  The way our body removes toxins is by creating more subcutaneous fat (externally visible fat) to store these toxins.  In other words, excess body fat formation is a protective mechanism to help our overworked liver in the job of removing toxins.  This effect is especially pronounced in women.  Eating clean, anti-inflammatory, nutrient dense foods and reducing toxin exposures as much as possible are key ways to restore normal liver function, in addition to reducing body fat.

Kids, Teens and NAFLD

The stats on NAFLD in kids/teens are startling. In the US, 17% of all 15-19 year olds and 38% of obese children have NAFLD. Males are affected twice as often as females. If your child is from a high risk ethnic group like the ones I mentioned (Indian, Chinese, Filipino, etc.) and/or is showing any signs of being overweight or insulin resistant, then the risk becomes even higher.

Keep in mind that like adults, children from Asian backgrounds (South Asian, East Asian, etc.) require less excess weight to develop fatty liver. They may appear skinny or be only slightly overweight, but if they come from a family with a strong history of diabetes and are not leading a healthy lifestyle, they may either already have fatty liver or be at very high risk. The principles of my body fat post here can be applied to children.

The teen years are when you need to be most aware of increased fatty liver risk. As school work piles on and college admissions pressure rises, teens spend less time exercising and more time studying. These study sessions often occur with friends in coffee houses, restaurants or other hangouts where junk foods are being consumed late into the night. I’ve had several parents bring in their high school or college students to see me for their fatty liver or other signs of insulin resistance.

Lifestyle Interventions to Prevent or Reverse NAFLD

The good news is that in my clinic we’ve had tremendous success in reversing fatty liver with lifestyle changes.  Some of the key changes include the following:

  1. Drop the SSBs: For individuals with NAFLD, I recommend complete elimination of SSBs or rare consumption only. If you don’t have fatty liver and want to avoid it, consider it an occasional treat only. Remember fatty liver won’t cause symptoms in its early stages so “feeling fine” doesn’t mean you can drink SSBs regularly.
  2. Limit Added Sugars: In addition to SSBs, reduce overall added sugar intake (desserts, processed foods, etc.). Sugar is everywhere and hidden in many non-sweet tasting packaged and processed foods. The general recommendation is no more than 9 teaspoons in men or 6 teaspoons daily in women. For my patients with NAFLD or other insulin resistant conditions, I try to aim for no more than 4-6 teaspoons daily. Eating mostly freshly prepared meals at home is the easiest way to hit this target since almost everything sold in stores and served by restaurants has added sugar.
  3. Reduce Excessive Carbohydrate Intake: As mentioned, even healthier non-sweet carbohydrates in abundance can trigger fat storage in the liver. For example, in my clinic, many of my patients who don’t even consume sweets and desserts, are getting fatty liver from excess intake of flatbreads (tortillas, chapatis, etc.), regular bread, noodles, and rice. Even healthier alternatives like brown rice, quinoa, and oats in abundance, especially in inactive individuals can drive fatty liver, diabetes, and other insulin resistant conditions.
  4. Move and Exercise More: Refer back to the earlier animation. In order to divert glucose traffic away from the liver and towards the muscle, your muscles need to be active every single day through more movement, cardio exercise, and strength training. Sitting for hours and going for a 20 minute walk in the evening isn’t sufficient. Get at least 7,000 steps each day, strength train at least twice a week, and get 150 minutes of moderate aerobic exercise weekly. If you’re not doing this, it may take very little extra sugar and carbohydrate to fuel fatty liver. Refer to my exercise blog post here for more details.
  5. Eliminate Artificial Fructose: Processed fructose like that found in high fructose corn syrup is a potent trigger for fatty liver. Many coffee shops, milk tea shops, and dessert shops use fructose syrup since it’s cheap and stores well.
  6. Avoid processed fats (like trans fats) and seed based oils (sunflower, corn, safflower, etc.) and consume healthier fats in moderation like monounsaturated fats (extra virgin olive oil, avocados, avocado oil, etc.), omega-3 fats from cold water oily fish, leafy greens and flaxseed. As a reminder, SSBs like frappuccinos and milk tea drinks might combine sugar, fructose, and/or heavy cream (saturated fat) which together in liquefied form can be a heavy load to the liver.
  7. Limit or eliminate alcohol intake: If you have NAFLD, it’s best to significantly reduce or eliminate alcohol altogether
  8. Supplements and Herbals: Be mindful of taking supplements and herbals which can be potentially toxic to the liver. Like alcohol, these can add an additional burden to a liver that is already infiltrated by fat.

Fatty liver is a potentially devastating condition that can affect all age groups and present and progress silently. You’re now armed with deep knowledge about the origins and the most effective ways to identify, prevent, and reverse fatty liver. Remember that even if you or your children have normal liver function tests, any signs of insulin resistance especially in combination with excess weight and the type of high risk diet I outlined, are enough reasons to take immediate action.

If you’ve been diagnosed with fatty liver, be sure to see your doctor regularly to help monitor this condition closely and you may need to work with a liver specialist for more intensive management.  Do everything possible to reverse NAFLD or prevent it in the first place.