Normal Weight but a Bulging Belly? Visceral Fat and Metabolic Disease

Have you ever reached for lighter clothes as the weather warms up, only to be startled by the belly fat that accumulated over the winter? Reducing the number on the scale is less important than ‘reducing visceral fat.’ Visceral fat is closely linked to blood sugar levels, insulin resistance, and hormonal changes, which can lead to metabolic health issues beyond just physical appearance. In this article, we will explore why visceral fat develops and how to manage it.

What is Visceral Fat?

Many people believe that if their weight is within the normal range, there are no health issues. However, in clinical practice, cases are frequently observed where metabolic disease risk increases if fat is concentrated in the abdomen, regardless of weight. This is particularly common in ‘skinny fat’ individuals who have thin limbs but a protruding belly. The key factor creating this difference is ‘visceral fat.’

Visceral fat refers to fat that accumulates inside the abdominal cavity around organs such as the liver, intestines, and pancreas. Unlike subcutaneous fat, which accumulates just under the skin, it is directly involved in metabolic activities and is closely linked to blood sugar, insulin, and fat metabolism. An increase in visceral fat can lead to the secretion of inflammatory substances and increased insulin resistance, impairing 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 diseases may increase. The Korean Society for the Study of Obesity diagnoses abdominal obesity when the waist circumference is 90 cm or more for men and 85 cm or more for women, recommending an evaluation of obesity-related disease risks. 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 shows 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 Disease

Because visceral fat is difficult to judge accurately by sight alone, 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 evaluate fat distribution and metabolic abnormalities beyond simple weight, comprehensive checks on fasting blood sugar, glycated hemoglobin (HbA1c), triglycerides, HDL cholesterol, and liver enzymes can be conducted. If necessary, abdominal CT or MRI may be used to measure the actual fat area within the abdominal cavity, and abdominal ultrasound or FibroScan may be performed to evaluate fatty liver. Recently, Bioelectrical Impedance Analysis (BIA) is also widely used to estimate visceral fat levels and abdominal fat mass.

Test Item	Information Provided	Reference Standard
BMI	Overall obesity assessment using height and weight	Under 18.5 Underweight / 18.5–22.9 Normal / 23.0–24.9 Overweight / 25+ Obese
Waist Circumference	Estimation of abdominal obesity and visceral fat risk	Men 90cm+ / Women 85cm+
Body Composition (BIA)	Muscle mass, body fat, and visceral fat level check	Estimates abdominal fat and body fat percentage
Fasting Glucose/HbA1c	Blood sugar control and insulin resistance assessment	Identifies prediabetes and diabetes risk
Triglycerides/HDL	Metabolic syndrome and cardiovascular risk assessment	Checks for high triglycerides and low HDL
Liver Enzymes/Ultrasound	Fatty liver and liver health assessment	Evaluates metabolic-associated fatty liver disease
Abdominal CT/MRI	Measures actual visceral fat area in the abdominal cavity	Precise assessment of visceral fat

Why Visceral Fat Doesn’t Disappear Just by Starving

Visceral fat is not effectively reduced simply by cutting food intake. The body perceives starvation as an ‘energy deficiency state’ and adjusts metabolism; in this process, fat may not decrease as expected, or muscle may be lost first. Therefore, sustainable lifestyle management is more important for visceral fat than extreme fasting. For modern people, long periods of sitting and low activity levels are major causes of visceral fat accumulation. Additionally, as we age, muscle mass decreases and fat distribution tends to shift toward the abdomen. Factors like high insulin resistance, lack of sleep, stress, frequent alcohol consumption, and late-night snacking can also make abdominal fat accumulate more easily. Repeated weight cycling (yo-yoing) can also cause body composition changes where fat re-accumulates primarily in the abdomen, so caution is needed.

Cause	Explanation
Extreme Fasting	Fat loss efficiency may drop due to muscle loss and lower basal metabolic rate
Insulin Resistance	Fat breakdown and blood sugar control functions may be impaired
Lack of Exercise	Reduced energy expenditure makes it easier for abdominal fat to accumulate
Sleep Deprivation/Stress	Can affect appetite regulation and metabolic balance
Alcohol/Late-night Snacks	Linked to increased risk of abdominal obesity and fatty liver

How to Reduce Visceral Fat

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

In terms of diet, ‘eating balanced’ is more important than simply ‘eating less.’ In particular, frequent consumption of refined carbohydrates like white rice, white bread, noodles, and snacks, as well as sugary drinks, can increase insulin secretion and induce fat storage. Conversely, a diet centered on protein, vegetables, and whole grains helps increase satiety and stabilize blood sugar fluctuations. It is also advisable to reduce late-night snacks and excessive drinking. For exercise, aim for at least 150 minutes of moderate-intensity aerobic exercise (brisk walking, cycling, swimming, etc.) per week, combined with strength training (squats, lunges, planks, etc.) 2–3 times a week. Aerobic exercise increases the rate at which fat is used as energy, helping to reduce visceral fat, while strength training helps maintain muscle mass and increase basal metabolic rate. Doing both together can be more effective for visceral fat reduction than either alone.

Additionally, lack of sleep affects the balance of appetite-regulating hormones, which can lead to overeating, and chronic stress can promote abdominal fat accumulation through increased cortisol secretion. Therefore, sufficient sleep and stress management must also be considered.

Lifestyle Habit	Action Item	Expected Effect
Diet	Ensure adequate protein and vegetables rather than just cutting rice	Increased satiety and prevention of overeating
Beverages	Reduce high-sugar coffee, juice, and sodas	Reduction in unnecessary sugar intake
Late-night Snacks	Finish eating 2–3 hours before bedtime	Reduced burden of nighttime fat accumulation
Exercise	Combine aerobic exercise like walking with strength training 2–3 times a week	Helps reduce visceral fat and maintain muscle mass
Sleep	Maintain a regular sleep schedule of 6–7+ hours a day	Maintains appetite control and metabolic balance
Stress	Use walking, stretching, or breathing exercises instead of binge eating	Helps prevent emotional eating

To manage visceral fat healthily, it is important to check changes in waist circumference and body composition improvement rather than focusing solely on the scale. Even if weight doesn’t change significantly, a decrease in waist circumference and improvements in blood sugar and triglycerides are positive signs.

Especially if you have abdominal obesity despite a normal weight, or if you have abnormalities in blood sugar, cholesterol, or blood pressure, it may be helpful to consult an endocrinologist to check for insulin resistance and metabolic disease. We hope you maintain a healthy daily life through habits that manage fat distribution and metabolic health rather than just simple weight loss.

Review: Professor Hwang Se-na, Department of Endocrinology

Field of Practice: Thyroid disease, diabetes, metabolic syndrome, menopause. Professor Hwang Se-na is an endocrinology specialist who graduated from Yonsei University Graduate School of Medicine. After serving as a clinical research assistant professor of endocrinology at Yonsei University Severance Hospital, she is currently practicing endocrinology at Chaum. Inquiry: Chaum Appointment Inquiry: 02-3015-5300 | Life Center Chaum, 4-1 Cheongdam-dong, Gangnam-gu, Seoul