Body Roundness Index (BRI)

BMI was designed in the 1830s as a population-level descriptor and only uses height and weight. It can't tell a 200-lb bodybuilder from a 200-lb sedentary person of the same height — both flag as 'obese.' BRI fixes the most important blind spot by adding waist circumference, which proxies for visceral adipose tissue (VAT), the metabolically active fat that surrounds the liver, pancreas, and intestines.

A 2024 JAMA Network Open study of 33,000+ NHANES participants found that BRI in the highest quintile was associated with significantly elevated all-cause mortality risk compared to the middle quintile, with a U-shaped curve at the very lowest values too (extreme leanness also carries risk). BMI showed weaker, less consistent associations in the same dataset.

Rough interpretation bands from the NHANES analyses: BRI under 3.4 is generally lean (lowest cardiometabolic risk in the middle of this range, slightly elevated mortality at the very low end). BRI 3.4–4.4 is moderate. BRI 4.5–5.5 indicates elevated visceral adiposity. BRI 5.5+ is associated with substantially higher cardiometabolic and mortality risk.

Because BRI uses waist circumference and height, it's especially useful for older adults, where BMI loses accuracy as muscle mass declines but visceral fat often increases. Two same-BMI 65-year-olds can have very different BRIs depending on where their fat sits.

Use a soft (non-stretch) tape measure. Stand relaxed, exhale normally, and measure at the level of the iliac crest — the top of your hip bone, roughly at or just above the navel. Don't suck in. The tape should be snug against skin without compressing it.

Take the measurement first thing in the morning before eating or drinking, repeat 2–3 times, and use the average. Day-to-day variation of 1–2 cm is normal from food, fluid, and digestion, so trends over weeks matter more than any single reading. A waist drop of 1 inch (2.5 cm) typically corresponds to ~4 lb of body fat lost and a meaningful improvement in BRI.

Waist-to-height ratio (WHtR) is the simplest competitor to BRI: waist divided by height, with a universal cutoff of 0.5 as the health-risk threshold. WHtR is easier to compute and well validated, but it treats the waist as a single number rather than modeling the body's three-dimensional shape. BRI captures more information about torso roundness and has shown stronger mortality prediction in some head-to-head studies.

Body fat percentage from the Navy method or DEXA directly measures adiposity but requires more inputs and equipment. BRI's advantage is that it needs only a tape measure and a calculator — no calipers, no hydrostatic tank, no expensive scan. For population-level screening and self-monitoring, BRI strikes a practical balance between accuracy and accessibility.

None of these metrics tell the whole story. Blood pressure, fasting glucose, lipid panels, and family history all matter. Use BRI as one data point in a broader health picture, not a final verdict.