Not all body fat is the same, and its location in the body can have significantly different effects on overall health. While people often think of fat as a single entity, there are two primary types, distinguished by where they are stored. Understanding the distinction between these fat depots is a first step in comprehending their unique roles and potential health consequences.
What is Subcutaneous Fat?
Subcutaneous adipose tissue (SAT) is the fat stored directly beneath the skin. It is the type of fat most familiar to people, as it can be physically pinched on the arms, legs, abdomen, and buttocks. This fat functions as the body’s primary energy reserve, storing excess calories to be accessed when needed. Beyond energy storage, subcutaneous fat acts as a protective layer, providing a cushion for muscles and bones and insulation to help maintain body temperature. While excessive amounts of any fat can be problematic, it is considered less of a health risk than its deeper counterpart.
What is Visceral Fat?
Visceral adipose tissue (VAT) is located deep within the abdominal cavity, where it surrounds important internal organs such as the liver, pancreas, and intestines. Unlike subcutaneous fat, visceral fat is not visible from the outside and cannot be pinched. An individual can have a relatively flat stomach and still carry a significant amount of this internal fat. This type of fat is not a passive storage depot; it is an active endocrine organ that can influence bodily functions. Its proximity to the portal vein, which carries blood from the intestines to the liver, means that substances released from visceral fat have direct access to the liver.
Health Risks and Metabolic Differences
The location of body fat has a direct impact on cardiometabolic health, with visceral fat being more pathogenic than subcutaneous fat. Visceral fat is more metabolically active and its individual fat cells are more likely to enlarge. This tissue releases inflammatory cytokines, substances that promote low-grade, systemic inflammation throughout the body. This chronic inflammation is a contributing factor to a variety of diseases. Fatty acids released from visceral fat travel directly to the liver, which can interfere with the liver’s ability to regulate insulin and lead to insulin resistance. Over time, this can lead to the development of type 2 diabetes and metabolic syndrome. Studies show a higher volume of visceral fat is strongly correlated with an increased risk of hypertension, dyslipidemia, and cardiovascular disease.
In contrast, subcutaneous fat is less metabolically disruptive. While it also stores energy, it does not release the same quantity of inflammatory substances directly to the liver. Research from the Framingham Heart Study has shown that while both fat types are associated with metabolic risk factors, visceral fat consistently shows a stronger association with an adverse metabolic profile. For example, one study found that for every standard deviation increase in visceral fat, the odds of having metabolic syndrome increased by a factor of 4.7 in women and 4.2 in men.
This does not mean that large amounts of subcutaneous fat are harmless. Overall obesity contributes to health problems, but the specific metabolic disturbances that lead to conditions like insulin resistance and heart disease are more directly linked to the amount of visceral fat a person carries.
Assessing Your Body Fat Composition
Because visceral fat is hidden deep within the body, it cannot be measured by simply looking in a mirror or stepping on a scale. One of the most accessible methods for estimating abdominal fat is measuring waist circumference. A tape measure is placed around the abdomen at the level of the navel. A waist circumference greater than 40 inches (102 cm) for men and 35 inches (88 cm) for women indicates a higher risk of health problems.
Another simple method is the waist-to-hip ratio (WHR), which involves dividing the waist measurement by the hip measurement. While these home methods provide a good estimate of risk, they do not directly measure visceral fat.
For a precise quantification of fat depots, medical imaging techniques are the gold standard. Technologies like computed tomography (CT) scans and magnetic resonance imaging (MRI) can accurately differentiate and measure the volume of both visceral and subcutaneous fat. Dual-energy X-ray absorptiometry (DEXA) scans can also provide detailed information about body composition. These clinical tools are not used for routine screenings due to cost and accessibility but are valuable in research and clinical settings.