What is visceral fat and why is it more dangerous than subcutaneous fat?
Visceral fat is more dangerous than subcutaneous fat because it acts directly on the liver, releases more inflammatory substances, and substantially raises your risk of cardiovascular disease and diabetes. This type of fat disappears relatively quickly through exercise and weight loss.
Visceral fat does not sit under your skin but deep inside the abdominal cavity, surrounding the intestines and stomach. From there, its breakdown products travel directly to the liver via the portal vein. Subcutaneous fat, which is found beneath the skin and around the hips and buttocks, does not have that direct connection to the liver.
Visceral fat is biologically far more active than subcutaneous fat. The fat cells are larger, better supplied with blood vessels, more densely innervated, and packed with inflammatory and immune cells. They respond strongly to stress hormones and break down more rapidly into free fatty acids. Subcutaneous fat does the opposite: it absorbs fatty acids from the blood and in doing so acts as a kind of buffer.
That higher activity comes at a cost. Too much visceral fat leads to a broad range of harmful changes all at once: higher triglycerides, more free fatty acids in the blood, release of inflammatory substances, insulin resistance in the liver, and more small, dense LDL particles that are more dangerous to blood vessels. 'Good' HDL cholesterol falls. That entire package substantially raises the risk of cardiovascular disease.
Abdominal obesity carries a greater risk of diabetes and cardiovascular disease than fat located around the hips and buttocks. In a Chinese cohort study of more than 8,000 people followed over nine years, a high visceral fat score was found to raise the risk of cardiovascular disease by a factor of 1.75 to 1.87. A higher visceral fat measurement was also associated with more than twice the risk of heart failure. In addition, there is a clear association with muscle loss in later life.
Good news: visceral fat responds relatively well to lifestyle changes. Weight loss through diet and exercise preferentially reduces visceral fat over subcutaneous fat, and this improves the risk profile. Medications such as liraglutide (a GLP-1 agonist, related to newer weight-loss drugs) reduced visceral fat in a double-blind study by an average of 12.5% compared with 1.6% in the placebo group. Nearly half of the participants experienced gastrointestinal complaints as a side effect.
All claims are based on one to two primary studies or reviews (PMID 19656312, 23303913, 40640908, 39604987, 39235730, 40749983, 34358471). No meta-analyses were used as a direct source. The findings are largely observational associations; proven causality is limited to a few mechanistic claims and the RCT on liraglutide.