Why it matters
You can’t judge visceral fat from the outside. Dr. O’Mara calls people who look lean but carry it TOFI: thin outside, fat inside. He has described a man with a 31-inch waist who still carried a lot of it. That’s why he relies on imaging rather than weight or BMI.
He also puts less weight on blood tests, which he says can swing from day to day. A scan shows the fat itself. Keep up with the checks your own doctor recommends.
How the measures compare
| Measure | What it tells you |
|---|---|
| BMI | Weight for height. It can’t show where fat is stored. |
| Waist size | Can miss visceral fat, especially in lean people. |
| Abdominal depthYour VFS | What Dr. O’Mara calls a “poor man’s MRI”: a useful screen, but not always right. |
| MRI | Shows visceral, heart and muscle fat directly. No radiation. |
When an MRI makes sense
- 01
Your VFS is V4 or higher
At V4 and above, a scan is the next step. It shows exactly where the fat is and how much there is.
- 02
You’re lean, but your score isn’t
That’s the TOFI pattern. A scan shows what a tape measure can’t.
- 03
You’re about to change how you live
Get a baseline, then rescan in about three months to see what’s working.
Work with Dr. O’Mara
His plans pair a full-body MRI with coaching. Scans are arranged in Minneapolis, MN, or at an MRI facility near you. Already have an MRI or CT? Ask about having it reviewed.
Opens drseanomara.com. Plans and prices are set by Dr. O’Mara’s practice.
Get an MRI of what your baseline is… and then repeat that in three months.
About Dr. Sean O’Mara
Dr. Sean O’Mara is an emergency medicine physician (MD, JD) and a retired U.S. Army colonel. He has spent more than a decade focused on visceral fat, tracks it in his clients with MRI, and is the author of Growing Better Not Older (2025).