[A Warning from a Hepatologist] Fattening More Than Carbohydrates! What Is the “Worst Carbohydrate” That Causes Fatty Liver (MASLD)?

Hello, I am Masaya Saito, Director of Saito Internal Medicine Clinic in Nishi-ku, Kobe.

“Even though I’m cutting back on rice and bread, I’m not losing weight for some reason.”

“I was told I have a fatty liver at my health checkup.”

If you are struggling with these concerns, the cause might not be carbohydrates themselves, but rather the “liquid carbohydrates” you are consuming without realizing it.

In this article, combining the latest medical knowledge with our perspective as liver specialists, we will explain the true nature of “isomerized sugar (such as high-fructose corn syrup)”—the number one ingredient causing fatty liver (MASLD)—and how to combat it.

10 Times Worse Than Glucose? The True Nature of “Isomerized Sugar”

The biggest enemy of fatty liver (MASLD) is the “isomerized sugar (such as high-fructose corn syrup)” lurking in juices, sweets, and seasonings. This is a liquid carbohydrate made by breaking down starch from corn and other sources, and it damages the liver for the following reasons:

• Immediately flips the fat accumulation switch Unlike glucose, fructose is metabolized almost exclusively in the liver. Therefore, the portion that is not used as energy the moment it is consumed is directly converted into neutral fat (triglycerides), turning liver cells into a “foie gras state.”
• Absorbed far too quickly Liquid carbohydrates require almost no effort to digest or break down, so they are rapidly absorbed into the body. This triggers rapid blood sugar spikes, impairs insulin function (insulin resistance), and creates a vicious cycle of storing even more fat in the liver.

Traps Lurking in Foods That Look “Healthy”

Isomerized sugar nonchalantly slips into foods that seem “good for your body.”

Food Item	Hidden Trap
Lactic acid bacteria drinks	You might drink them thinking they improve your intestinal environment, but they may actually be soaking your liver in sugar.
Mozuku seaweed in vinegar / Dressings	Vinegar itself is good for the liver, but commercially processed products often use large amounts of “high-fructose corn syrup” to make them easier to eat, so caution is required.
Sweet pastries (Kashi-pan)	In addition to sugar, they often contain trans fats such as margarine, making them a “heavy-damage combo” for the liver.

“Weight Gain of +10kg Since Age 20” Is a Limit Sign from Your Liver

The liver is called the “silent organ” and won’t cry out until more than two-thirds of it is damaged.

The progression route to liver fibrosis

When moving from a state where fat simply accumulates in the liver to MASH (Metabolic Dysfunction-Associated Steatohepatitis), which involves inflammation, “fibrosis” (hardening of the liver) begins.

Risks of leaving liver fibrosis untreated

As fibrosis progresses, it eventually reaches an irreversible state leading to liver cirrhosis and liver cancer. If you have gained more than 10 kg compared to when you were 20 years old, there is a high possibility that you are already standing at this entrance.

“3 Golden Habits” to Save Your Liver and Restore Metabolism

To break free from the trap of “isomerized sugar” and restart the liver’s role as a metabolic factory, please start the following measures starting today:

1. Check the ingredient label (Make a habit of looking at the back) Before buying food, look at the back label and check if “high-fructose corn syrup” or “glucose-fructose syrup” is listed. Simply avoiding these will dramatically reduce the burden on your liver. Ideally, switch your beverages to water, tea, or unsweetened coffee.
2. “Vegetables first” and “Chewing 30 times per bite” By eating vegetables (dietary fiber) at the beginning of a meal, you slow down the absorption of sugar. Chewing well not only gives you a sense of fullness, but it is also the strongest defense strategy to prevent rapid rises in blood sugar levels and prevent fat accumulation.
3. Consume meals rich in BCAA Muscles are “huge consumption centers” that consume sugar. Maintaining muscle mass by consuming BCAAs (branched-chain amino acids), which are abundant in chicken breast and other foods, takes over detoxification work from the liver and allows the liver to rest (liver care).

For Those Whose Liver Fibrosis Has Already Advanced: Treatment Through Regenerative Medicine

If your liver enzyme levels (such as ALT) do not easily decrease even though you work hard on diet and exercise or take medications, it may not be due to a lack of effort on your part. Instead, it might be a sign that the liver itself has developed “fibrosis (hardening)” and lost its ability to recover on its own.

At our clinic, we provide “liver regenerative medicine” using autologous adipose-derived stem cells.

Expected effects

The administered stem cells suppress chronic inflammation in the liver and promote the repair of hardened tissue, supporting the fundamental restoration of the liver’s original “metabolic power.”

Conclusion: Check ingredient labels carefully before buying food

That single bottle of juice you pick up at the supermarket determines whether you turn your liver factory into a cluttered mess or keep it clean. Avoid the “sweet temptation (isomerized sugar)” and polish your engine with high-quality protein and exercise.

If your liver has progressed to cirrhosis—meaning the engine is seized and won’t run—we believe liver regenerative medicine can be a beneficial treatment option.

If you have been diagnosed with cirrhosis and feel at a loss, why not first consult Saito Internal Medicine Clinic about your worries and anxieties? Whether by phone or online consultation, we are here for you. Our clinic understands how you feel and offers compassionate, personalized consultations. Please feel free to reach out to us without hesitation.