Normal BMI but full of visceral fat | The risk called TOFI

My weight hasn't changed, so I'm fine. People who think that way are the most at risk.

I was once told this by a business executive.

"I'm not fat, so I'm healthy."

His BMI was 22, he looked like he had a normal build, and he wore his suit well. At the time, I replied, "I suppose so." But when I looked at the visceral fat CT scan taken during his medical checkup, his internal organs were completely surrounded by fat.

In my experience as a personal doctor, I have seen many people who have a normal BMI but are packed with visceral fat. These are people who felt relieved after receiving an "all clear" on their health checkups.

In this article, I will write about a condition called TOFI, where visceral fat accumulates to dangerous levels even if your BMI is normal. I have designed this content to be immediately useful for those with lean fatty liver, hidden obesity, or those whose neutral fat and ALT levels are gradually rising despite receiving an A grade on their health checkups.

A scale does not show visceral fat

In the medical world, there is a concept called TOFI. It refers to a state where one is thin on the outside but full of fat on the inside.

They look normal. Their weight is normal. Their BMI is within the standard range. Yet, there are people who have fat accumulating in places that cannot be seen from the outside, such as around their internal organs and in their liver.

This concept was clearly presented in a paper by a research team at Imperial College London. They examined 477 people using MRI and reported that BMI and appearance alone cannot detect visceral fat or intrahepatic fat. TOFI has been proposed as a type with high metabolic risk¹⁾.

Even though the number on the scale is normal, a dangerous condition is already progressing inside the body.

In my practice, this pattern is not uncommon. It is especially prevalent among male executives in their 40s and older. Their diet consists mainly of eating out, and they get zero exercise. But because they don't eat much, their weight doesn't change. This is the most common pattern.

FFMI is an index that divides the "contents" of weight and BMI into muscle and fat. It can be calculated in 30 seconds, allowing you to track whether what you have lost is fat or muscle. I wrote about this index in the members-only article "Am I obese?" The blind spot of BMI I thought about after being asked by Koji Kato | Recommendations for FFMI.

Why visceral fat increases even if you don't eat much

The lifestyle of the executive mentioned at the beginning was like this: No exercise. Meals were mainly eating out and alcohol. But because the amount he ate was small, he didn't gain weight.

He thought, "I'm fine because I don't eat much." In fact, his weight had never changed. I understand the sentiment. If the amount you eat hasn't increased, there's no reason to gain weight. That's what people usually think.

But the problem is not the "amount," but the "content."

Even if you don't eat a large amount, if you continue a lifestyle of eating out with a focus on carbohydrates, fats, and alcohol, combined with a lack of exercise, the places where fat accumulates can change. This is a problem that cannot be seen by weight alone. This is where many people are mistaken.

If you don't exercise, your muscle mass decreases year by year. As muscle decreases, the places to store glucose also decrease. Into this environment, business dinners, finishing meals with carbohydrates, alcohol before bed, and sugary drinks continue to enter.

Your weight doesn't increase. But inside, the destination for excess energy is gradually changing. Subcutaneous fat shows on the outside. That's why you notice when you've "gained weight."

Visceral fat doesn't show up on the scale or in the mirror.

That's why it's dangerous.

By the way, I've been training for a long time, so I'm one of those people who is 'heavy with muscle,' but even so, there was a time when I slacked off on weight loss and my visceral fat became a serious problem. Even if you have a long history of strength training, it accumulates the moment you let your guard down.

Visceral fat is not just fat.

What happens if you leave a TOFI state untreated?

Visceral fat isn't just sitting there. When it increases too much, the fat itself begins to release substances that cause inflammation (adipocytokines). These circulate throughout the body, causing harm little by little.

As a result, insulin (the hormone that lowers blood sugar) becomes less effective, increasing the risk of diabetes. At the same time, this inflammation continues sluggishly, damaging the inner walls of blood vessels.

Arteriosclerosis progresses quietly from things like this.

There is a 2013 meta-analysis (from the internal medicine journal Annals of Internal Medicine). People who have normal weight but poor blood test results or blood pressure numbers have, compared to people of the same weight with clean test results, a risk of death or cardiovascular events that is about 3.1 times higher ²⁾.

However, this is a meta-analysis of observational studies. It is not a figure that tracks only death, but a figure that counts death and cardiovascular events together. One cannot go so far as to say that 'metabolic abnormalities are the direct cause of increased deaths and cardiovascular events.' Even so, it is clear that it is dangerous to feel safe based on BMI alone.

'I'm not fat, so I won't get diabetes'

'I don't feel anything, so I'm fine'

Both are dangerous assumptions.

This pattern, which tends to go unnoticed, is actually the scariest. You suddenly collapse without feeling any changes in your physical condition. It is also directly linked to the continuation of your business. As a personal doctor, this is the one risk I make sure to convey over and over again.

Even if you are thin, you can get fatty liver

People with a lot of visceral fat are also prone to fat accumulating in their liver. This is what is known as fatty liver.
Fatty liver was once treated as something like 'well, it's not a big deal.' I remember that even when I was a student, the descriptions in textbooks were light.

However, recent research has significantly changed this perception. Some cases of fatty liver progress to hepatitis (MASH⁷⁾), leading to cirrhosis and liver cancer.
And this MASH is not a disease that only affects overweight people. Even if your BMI is normal, it can occur if fat accumulates in the liver and metabolic abnormalities overlap.

In an analysis from 2020 that collected research from around the world, it was reported that fatty liver in non-overweight people has reached a proportion that cannot be ignored globally³⁾.

You can get fatty liver without drinking alcohol. You can get fatty liver without being overweight.

Many people still don't know this fact.

Moreover, in the case of Japanese people, lean-type fatty liver is not rare. In a 2021 Japanese meta-analysis that integrated 73 studies and about 260,000 people,about 20% of people with fatty liver were 'lean types' with a BMI under 23⁴⁾.

One in five.

'I'm thin, so I probably don't have fatty liver' doesn't hold up.
I delved into the topic of fatty liver itself along with new papers in Commonalities of people whose fatty liver doesn't heal even if they lose weight. You can understand why some people still have fatty liver even after losing weight.

The numbers you should look back at on your health checkup report first

The first thing to do to lower the risk of TOFI is to look back at your health checkup report.
Even if your BMI is normal, please be careful if the following numbers are gradually getting worse.

• Triglycerides

• HDL cholesterol

• HbA1c

• ALT

• γ-GTP

• Blood pressure

• Waist circumference

You need to look at these comprehensively, not just diagnose based on one. If all of these are shifting toward the bad side, you should think, 'My weight hasn't changed, but the inside of my body might have.'

What is scary in outpatient care is not a single abnormal value, but a pattern of gradually getting worse within the normal range. Triglycerides are higher than last year. HDL has dropped. ALT has risen. HbA1c has gone up slightly. Waist circumference has increased. Blood pressure has risen.

Even if everything is graded A, the picture changes when you line them up.

When you read the numbers on your health checkup report side-by-side, what comes into view? I wrote in detail about the TG/HDL ratio, year-over-year changes in ALT, and even how eGFR drops in Why you shouldn't stop at an all-A health checkup.

How is the amount of visceral fat measured?

You cannot tell the amount of visceral fat just from the numbers on a scale.

This is where abdominal ultrasounds and blood tests from health checkups come in handy. An ultrasound can tell you if you have a fatty liver. However, if it is mild, it might be missed. If you combine it with blood test data such as triglycerides, HbA1c, and ALT, you can pick up the possibility that visceral fat is accumulating.

However, even if an ultrasound can tell you 'whether or not you have a fatty liver,' it is not a test that accurately measures the amount of visceral fat. Also, in blood tests, there are cases where a fatty liver is hidden even if ALT is normal.

That is why what I recommend to business owners is to take it one step further for those who need it and get an abdominal CT scan during a comprehensive medical examination (dock).

Just by taking one slice at the level of the navel, you can see the visceral fat area (VFA) as a numerical value. In Japan, 100cm² or more has been used as a guideline for visceral fat-type obesity⁸⁾.

Of course, CT involves radiation exposure, so it is not a test that everyone should do every year. I believe it is a test that should be chosen by those who need it after checking their health checkup report, waist circumference, lifestyle background, and family history.

VFA, fasting insulin, ApoB, high-sensitivity CRP, carotid ultrasound. These items are often not included in standard health checkups. If you don't look for it, you won't find it.

Among these, ApoB is an indicator that can pick up the risk of arteriosclerosis even if LDL is normal. I wrote about why you should measure it even if LDL is normal in this article.

I wrote in quite some detail about how far you should go in adding test items that cannot be picked up by 'no abnormalities' in a health checkup in the members-only article The blind spot of all A's. The complete version of tests and lifestyle protocols to truly protect your blood vessels.

First, suspect 'how much visceral fat you might have' with numbers. That is the starting line.

Does reducing food intake solve the problem?

So, should you just reduce the amount you eat? The cause of TOFI is not just simple overeating. It occurs due to a combination of diet content, lack of exercise, and a decrease in muscle mass.

Business owners who eat out frequently, even if they eat small portions, tend to lean toward carbohydrates, fats, and alcohol. A rice bowl for lunch. A little sashimi and alcohol for dinner. Noodles to finish. Just coffee in the morning. With this, it is hard to gain weight, but visceral fat and fatty liver accumulate easily.

When I talk about diet in outpatient care, I first tell them to 'change only three things.' Since doing everything is impossible, I start with three things that will be effective.

1. Increase protein intake
People who eat out often are not getting enough protein, more than they realize. For those without kidney problems, the guideline is 1.2g per kg of body weight per day. If you weigh 70kg, that is about 84g. Note that this is the baseline for people without exercise habits, so those who have started strength training should increase it further (1.6g per kg of body weight).

There is a theory that if you do not get enough protein, your body will overeat in search of the deficit. This is called the Protein Leverage Hypothesis, which I wrote about in this article along with the story of why you cannot stop eating potato chips.

2. Reduce the frequency of alcohol
Alcohol promotes fat synthesis in the liver. Do not think, 'It is fine because the amount is small'; think in terms of total volume and frequency. If you drink every day, start by creating a few days a week where you do not drink.

3. Reduce sugary drinks and refined carbohydrates
You do not need to completely stop eating white rice, bread, noodles, or sugary drinks. Just reducing your staple food intake by 20 to 30 percent or replacing sugary drinks with water or tea will change the burden on your liver.

What is particularly overlooked is the high-fructose corn syrup found in soft drinks and energy drinks. Fructose enters the liver easily and is prone to being converted into fat. If you drink these every day, just changing this will be enough.

Why strength training for visceral fat?

Aerobic exercise is also important, but for TOFI, what I strongly recommend is strength training.

The reason is simple: muscles are a large reservoir for blood sugar.

If muscle mass increases, not only does your basal metabolism improve, but your ability to absorb blood sugar also increases. Insulin also becomes more effective. Strength training works on the root cause of visceral fat accumulation.

A 2022 meta-analysis confirmed that visceral fat decreased with strength training alone⁵⁾. Since it is a synthesis of RCTs (randomized controlled trials), it is easier to say it 'worked' than in observational studies.

Another 2021 meta-analysis of 34 studies involving 2,285 people reported that visceral fat decreased with strength training alone, even without dietary restrictions⁶⁾.

Although this is not a study targeting only TOFI, it serves as a basis for expecting strength training to be a means of mobilizing visceral fat.

However, this does not mean that 'everything will be solved by strength training alone without changing your diet.' The effect is small to moderate rather than dramatic. Even so, there is value in starting with strength training even during periods when you cannot immediately change your diet. If combined with dietary improvement, the effect is even greater.

The minimum line I often convey is twice a week, 30 minutes per session.
If you can go to the gym, squats, leg presses, lat pulldowns, and chest presses are fine. If you cannot go to the gym, bodyweight squats and push-ups are fine to start with.
It is more important not to let it reach zero than to have a perfect menu.

Look at the inside of your body, especially if your weight has not changed

'I am not fat, so I am fine' is the most dangerous assumption.

Even if the number on the scale is normal, fat may be quietly accumulating inside your body, and the risks of blood sugar abnormalities, arteriosclerosis, and fatty liver may be progressing.

This is the tricky part. It doesn't show up in your appearance, your weight, or any subjective symptoms. That is precisely why you need to verify it with numbers. As a personal doctor, this is what I tell business executives.

You look at your company's financial statements every year, right? I want you to open your own body's financial statement at least once a year as well.

My weight hasn't changed, so I'm fine.

That feeling itself isn't wrong. It's just that you're looking in the wrong place.

The answer isn't on the scale; it's in the contents of your health checkup report.

Summary

• TOFI is a state where visceral fat and fatty liver are hidden more than they appear, even with a normal BMI.

• Even if your BMI is normal, people with poor blood test results or blood pressure numbers may fall into a high-risk group for cardiovascular disease.

• About 20% of people with fatty liver in Japan are thin. Fatty liver can occur even if you are thin.

• In your health checkup report, track your triglycerides, HDL, HbA1c, ALT, γ-GTP, blood pressure, and waist circumference.

• If you are concerned, consider an abdominal ultrasound and blood tests, and if necessary, an abdominal CT or additional examinations.

• Even with strength training alone, there is room for visceral fat to move, but the effect is even greater when combined with aerobic exercise and dietary improvements.

Thank you for reading this far.
If you found this helpful, it would be a great encouragement if you could give it a 'Like'. I publish health stories that I have tested on my own body, covering various themes, about once every few days.
I would be very happy if you would follow me.

For those who want to know more deeply (Related articles)

From here on, it is recommended to read by dividing it into two parts: strength training and countermeasures for business dinners.

▼ Where to start strength training
No need for pushing to failure or hypertrophy ranges | Explanation of the latest US strength training guidelines (Members only) I have translated how to think about pushing to failure, weight, repetitions, and number of sets into practice based on the latest US guidelines. This is for those who want to go beyond 30 minutes twice a week.

▼ Realistic ways to change for those who cannot reduce business dinners
Subtractive eating methods that lowered an executive's numbers without reducing business dinners (Members only)
Yogurt 30 minutes before the dinner, canned mackerel the next morning, and cutting the final course. I have summarized the methods I actually provide in outpatient care, including specific examples of how triglycerides and ALT moved.

Announcement of the membership 'Dr. Mosari Lab'
I operate a membership called 'Dr. Mosari Lab'. I write about more in-depth topics that cannot be released on X or free notes.

• Content I actually talk about in outpatient care as a doctor for executives

• Records of what worked and what didn't, tested on my own body while reading papers

• How to read test values and how to choose supplements and medicines

• Member-only Q&A board

For 1,000 yen per month, you get unlimited access to all articles. You can cancel at any time if it's not for you. If you're interested, please take a look.

*This article is intended to provide general health and medical information and does not constitute diagnosis, treatment, or medical advice for any specific individual. If you have health concerns, please be sure to consult a medical institution. The author cannot be held responsible for the consequences of any actions taken based on the information in this article.

References
1) Thomas EL, Parkinson JR, Frost GS, Goldstone AP, Doré CJ, McCarthy JP, Collins AL, Fitzpatrick JA, Durighel G, Taylor-Robinson SD, Bell JD. The missing risk: MRI and MRS phenotyping of abdominal adiposity and ectopic fat. Obesity (Silver Spring). 2012;20(1):76-87. doi:10.1038/oby.2011.142. PMID:21660078.

2) Kramer CK, Zinman B, Retnakaran R. Are metabolically healthy overweight and obesity benign conditions?: A systematic review and meta-analysis. Ann Intern Med. 2013;159(11):758-769. doi:10.7326/0003-4819-159-11-201312030-00008. PMID:24297192.

Schulze MB. Metabolic health in normal-weight and obese individuals. Diabetologia. 2019;62:558-566. doi:10.1007/s00125-018-4787-8.

3) Ye Q, Zou B, Yeo YH, et al. Global prevalence, incidence, and outcomes of non-obese or lean non-alcoholic fatty liver disease. Lancet Gastroenterology & Hepatology. 2020;5(8):739-752.

4) Ito T, Ishigami M, Zou B, et al. The epidemiology of NAFLD and lean NAFLD in Japan: a meta-analysis. Hepatology International. 2021;15:366-379.

5) Wewege MA, Desai I, Honey C, et al. The Effect of Resistance Training in Healthy Adults on Body Fat Percentage, Fat Mass and Visceral Fat. Sports Medicine. 2022;52(2):287-300.

6) Khalafi M, Malandish A, Rosenkranz SK, et al. Effect of resistance training with and without caloric restriction on visceral fat. Obesity Reviews. 2021;22(9):e13275.

7) Rinella ME, Lazarus JV, Ratziu V, et al. A multisociety Delphi consensus statement on new fatty liver disease nomenclature. Hepatology. 2023;78(6):1966-1986. doi:10.1097/HEP.0000000000000520. PMID:37363821.

8) Hiuge-Shimizu A, Kishida K, Funahashi T, et al. Absolute value of visceral fat area measured on computed tomography scans and obesity-related cardiovascular risk factors in large-scale Japanese general population (the VACATION-J study). Ann Med. 2012;44(1):82-92. doi:10.3109/07853890.2010.526138. PMID:20964583.