Subcutaneous Fat

Subcutaneous fat lives in the hypodermis, the deepest layer of skin, where specialized cells called adipocytes store energy as triglycerides. This layer covers nearly the entire body and does practical jobs beyond storage: it insulates against cold, cushions bone and muscle from impact, and buffers between meals so your body has fuel to draw on when you are not eating.

When you eat more calories than you burn, insulin signals these fat cells to pull fatty acids out of the bloodstream and store them as triglycerides, a process called lipogenesis. In a calorie deficit, falling insulin and rising catecholamines trigger the reverse process, releasing stored fat back into the blood to be burned for fuel. Subcutaneous fat cells lack the direct line to the liver that visceral fat cells have, so the fatty acids and inflammatory signals they release enter general circulation gradually rather than flooding the liver. That is the core distinction from visceral fat: subcutaneous fat is mostly a passive storage depot, while visceral fat is an active source of inflammatory signaling.

Because subcutaneous fat sits close to the surface, it is the layer skinfold calipers measure directly, pinching a fold of skin at sites like the triceps, abdomen, and suprailiac crest and using the thickness to estimate total body fat percentage. DEXA scans and bioelectrical impedance scales estimate whole body fat without separating subcutaneous from visceral, while MRI and CT imaging can visualize the two layers directly, though they are rarely used outside clinical or research settings.