Normal Weight, But Only a Protruding Belly? Visceral Fat and Metabolic Diseases

Have you ever taken out lighter clothes in the suddenly warmer weather, only to be surprised by the belly fat you gained over winter? More important than simply reducing the number on the scale is ‘visceral fat reduction’. Visceral fat, in particular, is closely linked to blood sugar, insulin resistance, and hormonal changes, which can lead to metabolic health issues beyond just body shape. In this article, we will explore why visceral fat accumulates and how to manage it.

What is Visceral Fat?

Many people believe that if their weight is within the normal range, they will have no health problems. However, in clinical practice, it is common to see cases where fat is concentrated in the abdomen regardless of weight, increasing the risk of metabolic diseases. In particular, there are many instances of increased visceral fat in individuals with thin arms and legs but a protruding belly, often referred to as ‘skinny fat’. The key factor creating this difference is ‘visceral fat’.

Visceral fat refers to fat accumulated inside the abdominal cavity, around organs such as the liver, intestines, and pancreas. Unlike subcutaneous fat, which accumulates directly under the skin, visceral fat is directly involved in metabolic activity, making it closely linked to blood sugar, insulin, and fat metabolism. An increase in visceral fat can lead to increased secretion of inflammation-related substances and insulin resistance, which can impair blood sugar control. If these changes persist, the risk of metabolic diseases such as prediabetes, metabolic dysfunction-associated steatotic liver disease (MASLD), dyslipidemia, hypertension, and cardiovascular and cerebrovascular diseases can also increase. The Korean Society for the Study of Obesity diagnoses abdominal obesity in Koreans as a waist circumference of 90cm or more for men and 85cm or more for women, and recommends evaluating the increased risk of obesity-related diseases if abdominal obesity is present. Furthermore, the Korean Diabetes Association’s ‘Diabetes Cardiovascular Disease FACT SHEET 2024’ emphasizes that abdominal obesity and insulin resistance are closely related to an increased risk of cardiovascular disease. This indicates that the location and distribution of fat can have a more direct impact on metabolic health than simple body weight.

The Relationship Between Visceral Fat and Metabolic Diseases

Visceral fat is also difficult to accurately assess visually, so various diagnostic indicators are evaluated together. Most basically, waist circumference and BMI are checked, and recently, body composition analysis and metabolic tests are often performed together. To assess fat distribution and metabolic abnormalities rather than just body weight, fasting blood sugar, HbA1c, triglycerides, HDL cholesterol, and liver enzyme levels can be comprehensively checked. If necessary, abdominal CT or MRI may be used to measure the actual visceral fat area within the abdominal cavity, and abdominal ultrasound or liver scan may be performed to evaluate fatty liver. Recently, methods to estimate visceral fat levels and abdominal fat mass through body composition analysis (BIA) are also widely used.

Test Item	Information Provided	Reference Criteria
BMI	Overall obesity assessment using height and weight	Under 18.5 underweight / 18.5~22.9 normal / 23.0~24.9 overweight / 25 or more obese
Waist Circumference	Estimation of abdominal obesity and visceral fat risk	Men 90cm or more / Women 85cm or more
Body Composition Analysis (BIA)	Muscle mass, body fat, visceral fat level check	Abdominal fat and body fat percentage can be estimated
Fasting Blood Sugar · HbA1c	Blood sugar control status and insulin resistance assessment	Prediabetes · diabetes risk check
Triglycerides · HDL Cholesterol	Metabolic syndrome and cardiovascular disease risk assessment	Check for increased triglycerides · decreased HDL
Liver Enzymes · Abdominal Ultrasound or Liver Scan	Fatty liver and liver health status assessment	Metabolic dysfunction-associated steatotic liver disease can be assessed
Abdominal CT · MRI	Actual measurement of visceral fat area within the abdominal cavity	Precise visceral fat assessment possible

Why Visceral Fat Doesn’t Disappear Just by Starving Yourself

Visceral fat does not effectively decrease simply by reducing food intake. The body perceives starvation as an ‘energy deficit state’ and regulates metabolism, which can lead to fat not decreasing as expected, or even muscle loss occurring first. Therefore, for visceral fat, sustainable lifestyle management is more important than extreme dieting. For modern people, a sedentary lifestyle with prolonged sitting and low physical activity is one of the causes of visceral fat accumulation. This is compounded by the tendency for muscle mass to decrease and fat distribution to shift towards the abdomen with age. Furthermore, if insulin resistance is high, or if there is a lack of sleep, stress, frequent alcohol consumption, and late-night eating, abdominal fat can accumulate more easily. Repeated weight fluctuations can also cause changes in body composition, leading to fat re-accumulation primarily in the abdomen, so caution is needed.

Cause	Explanation
Excessive Dieting	Muscle loss and decreased basal metabolic rate can reduce fat loss efficiency
Insulin Resistance	Fat breakdown and blood sugar control function may be impaired
Lack of Exercise	Reduced energy consumption makes abdominal fat accumulation easier
Sleep Deprivation · Stress	Can affect appetite control and metabolic balance
Alcohol · Late-Night Eating	Can be associated with increased risk of abdominal obesity and fatty liver

How to Reduce Visceral Fat

To reduce visceral fat, it is important to adjust diet, exercise, sleep, and stress management together. According to data from the Korea Disease Control and Prevention Agency, abdominal obesity is closely related to visceral fat accumulation and can worsen insulin resistance, increasing the risk of metabolic syndrome.

In terms of diet, ‘eating a balanced diet’ is more important than simply ‘eating less’. Frequent consumption of refined carbohydrates like white rice, white bread, noodles, and snacks, as well as sugary drinks, can increase insulin secretion and promote fat accumulation. Conversely, a diet rich in protein, vegetables, and whole grains helps increase satiety and stabilize blood sugar fluctuations. It is also advisable to reduce late-night eating and excessive alcohol consumption. For exercise, aim for at least 150 minutes of moderate-intensity aerobic exercise per week (such as brisk walking, cycling, swimming), and combine it with strength training 2-3 times a week (such as squats, lunges, planks). Aerobic exercise helps reduce visceral fat by increasing the proportion of fat used as an energy source, while strength training helps maintain muscle mass and increase basal metabolic rate. Performing both together can be more effective in reducing visceral fat than either alone.

Furthermore, lack of sleep can affect the balance of appetite-regulating hormones, leading to overeating, and chronic stress can promote abdominal fat accumulation by increasing cortisol secretion. Therefore, sufficient sleep and stress management should also be considered.

Lifestyle Habit	Action Item	Expected Effect
Diet	Focus on sufficient protein and vegetables rather than just reducing rice portion	Increased satiety and prevention of overeating
Beverages	Reduce high-sugar coffee, juices, and sodas	Reduced unnecessary sugar intake
Late-Night Eating	Finish meals 2-3 hours before bedtime	Reduced burden of nocturnal fat accumulation
Exercise	Combine aerobic exercise (e.g., walking) with strength training 2-3 times a week	Helps reduce visceral fat and maintain muscle mass
Sleep	Maintain regular sleep of 6-7 hours or more per day	Appetite control and metabolic balance maintenance
Stress	Use walks, stretching, and breathing exercises instead of emotional eating	Helps prevent emotional eating

To manage visceral fat healthily, it is important to monitor changes in waist circumference and improvements in body composition, rather than just focusing on the number on the scale. Even if your weight doesn't change significantly, a reduction in waist circumference along with improvements in blood sugar and triglycerides can be seen as positive changes.

Especially if you have abdominal obesity despite a normal weight, or if it is accompanied by abnormal blood sugar, cholesterol, or blood pressure, it may be helpful to consult an endocrinologist to check for insulin resistance and metabolic diseases. Maintain a healthy daily life by adopting habits that manage fat distribution and metabolic health together, rather than just simple weight loss.

Reviewed by: Professor Hwang Sena, Department of Endocrinology

Clinical Areas: Thyroid disease, diabetes, metabolic syndrome, menopause. Professor Hwang Sena is a specialist in endocrinology. After graduating from Yonsei University College of Medicine, she served as a clinical research assistant professor in the Department of Endocrinology at Severance Hospital, Yonsei University, and currently practices endocrinology at Chaum. Inquiries: Chaum Appointment Inquiries: 02-3015-5300 | 4-1 Cheongdam-dong, Gangnam-gu, Seoul, Life Center Chaum

Frequently Asked Questions

Can I have abdominal obesity even if my weight is normal?

Yes, 'skinny fat' (마른 비만) can occur, where fat is concentrated only in the abdomen regardless of weight. This condition involves excessive visceral fat accumulation around organs, even with thin limbs. If left unmanaged, it increases the risk of metabolic diseases like prediabetes or cardiovascular disease, thus requiring management.

What are the waist circumference criteria for diagnosing abdominal obesity?

According to the Korean Society for the Study of Obesity, abdominal obesity is diagnosed when the waist circumference is 90cm or more for men and 85cm or more for women. If your waist circumference exceeds these criteria, it is advisable to consult with medical professionals to assess whether there is an increased risk of obesity-related metabolic diseases, beyond just a body shape concern.

Can I lose visceral fat by starving myself?

No, extreme starvation is not effective for reducing visceral fat. When your body perceives starvation as an energy deficit, it adjusts its metabolism, which means fat reduction is minimal, and muscle mass may decrease first, leading to a drop in basal metabolic rate.

What kind of exercise should I do to reduce visceral fat?

Combining aerobic exercise and strength training is most effective. Performing moderate-intensity aerobic exercises like brisk walking or swimming for more than 150 minutes per week, along with strength training such as squats or planks 2-3 times a week, significantly helps in reducing visceral fat and maintaining muscle mass.

How is visceral fat tested?

Visceral fat is primarily estimated through waist circumference and body composition analysis. Blood tests for fasting blood sugar, triglycerides, and liver enzymes are performed to check for metabolic abnormalities. If necessary, abdominal CT or ultrasound may be used to precisely evaluate the actual intra-abdominal fat area and fatty liver.