Visceral fat: the fat you can't see in the mirror
Most body fat sits just under the skin. That's subcutaneous fat, the kind you can pinch. Visceral fat is different. It lives deep in the abdomen, packed around the liver, intestines, pancreas and kidneys, and you can't pinch it or reliably see it.
Why it matters more than weight
Visceral fat is metabolically active. It releases fatty acids and inflammatory signals straight into the blood that flows to the liver. Large population studies tie it more closely than overall weight to type 2 diabetes, fatty liver disease, high blood pressure and heart disease.
That's why two people with the same weight can have very different risk. Someone who looks slim can carry a lot of visceral fat, a pattern sometimes called "thin outside, fat inside."
What drives it up
- Diets heavy in added sugar, sweet drinks and refined starch
- Too little movement, especially long hours of sitting
- Poor sleep and chronic stress, which raise cortisol
- Alcohol, particularly in larger amounts
- Age and, for women, the hormonal shift around menopause
The good news
Visceral fat tends to respond to changes in diet and activity sooner than subcutaneous fat. Scans often show it shrinking before the scale moves much. That's part of why doctors who use MRI, like Dr. Sean O'Mara, find it a useful way to show patients their progress.
How to measure it
- Waist-to-height ratio. Waist measured at the belly button divided by height. Under 0.5 is the usual target. It's a rough but free proxy.
- Bioimpedance scales. Some home scales estimate visceral fat. Useful for trends, not precise numbers.
- DEXA. A low-dose X-ray body scan that estimates visceral fat in minutes.
- CT and MRI. The most accurate measures. MRI uses no radiation, which makes it the better choice for repeat scans.