A new body shape metric predicts cancer risk — but with limits

What just happened

A new study published in the International Journal of Cancer has examined whether the Body Roundness Index — a measure of how centrally adipose a person’s body is — predicts cancer outcomes better than BMI. The research used UK Biobank data on 470,116 adults (253,458 female; median age 57 years), followed for a median of 13.7 years, during which 63,135 incident cancer cases occurred.

The Body Roundness Index, or BRI, is a formula that uses waist circumference and height to quantify central — visceral — adiposity. Unlike BMI, which measures total weight relative to height, BRI attempts to capture how much fat is distributed around the abdomen specifically. Visceral fat is metabolically active and has been associated with systemic inflammation, insulin resistance, and altered hormone levels — all plausible biological pathways to increased cancer risk.

The headline findings: higher BRI was associated with increased incidence of 13 cancer types, including uterine (hazard ratio 1.31), liver (1.20), kidney (1.17), and stomach (1.13) cancers. BRI was also associated with increased cancer mortality from breast and prostate cancers, and with higher all-cause mortality (hazard ratio 1.07).

The research team concluded that visceral adiposity may represent an “important yet overlooked determinant of cancer risk.”

Both-and

The finding that matters — and the one that complicates it

The most clinically significant element of this study is not the new metric itself. It is the consistent signal across 13 cancer types: central fat distribution is linked to cancer risk across a broad range of body systems. That is not a novel hypothesis — visceral adiposity has been associated with metabolic syndrome, cardiovascular disease, type 2 diabetes, and several cancers for well over a decade. But this study adds a large prospective dataset (470,000 participants, nearly 14 years of follow-up) to that body of evidence.

The complication: when BRI and BMI were compared head-to-head in this dataset, “no superior metric emerged.” BRI did not clearly outperform BMI. The researchers’ argument is that BRI, by specifically capturing central adiposity, provides a mechanistically informative measure — that it tells us why fat distribution matters for cancer, not just that weight matters. That is a legitimate scientific contribution.

But from a practical standpoint, a metric that requires a new formula, generates new reference ranges, and adds calibration complexity — while not demonstrably outperforming BMI at the population level — may add limited clinical value in the general practice consultation.

What the UK Biobank limitation means for Australian practice

The UK Biobank is largely composed of participants of European ancestry. The researchers explicitly noted that their findings “may not generalise to non-European populations” — which is a significant caveat for a country where approximately one-third of the population has a non-European heritage background.

Body fat distribution differs by ancestry. South Asian populations, for example, tend to carry visceral fat at lower BMI thresholds than European populations — a known discordance that the NHMRC and Diabetes Australia have addressed by recommending lower waist circumference action thresholds in some groups. A formula calibrated on UK Biobank data will not automatically translate to equivalent predictive accuracy in Aboriginal and Torres Strait Islander patients, patients of Asian background, or Pacific Islander communities — groups who attend Australian general practice and for whom cancer risk assessment is clinically important.

This does not mean the BRI concept is wrong. It means that before new clinical cut-offs or calculators are built around BRI for Australian practice, validation in an Australian cohort is needed.

The already-available tool

Waist circumference measurement is not new. RACGP guidelines and metabolic syndrome criteria already recommend it as part of cardiovascular and metabolic risk assessment. Action thresholds — >94 cm in men, >80 cm in women (ethnicity-adjusted in some populations) — are established and in clinical use.

What this study reinforces is that the measurement matters — not just for cardiovascular and metabolic risk, but potentially for cancer risk screening conversations as well. The gap it highlights is not that GPs need a new formula. It is that waist circumference is already in the guidelines and is underused in routine clinical assessment.

2 cents

For general practice this week:

You probably don’t need to start calculating BRI. The finding that BMI and BRI perform similarly at the population level means the new formula does not clearly replace the tools you already have. What it does do is add weight — so to speak — to measuring waist circumference in patients where BMI alone may be misleading: people who carry significant abdominal fat at normal-to-moderate BMI, or who have lost muscle mass.

Visceral fat is a cancer risk factor in the evidence base. The size of the UK Biobank study and the consistency across 13 cancer types makes that difficult to dismiss, even acknowledging the European-cohort limitation. When discussing cancer risk reduction with patients, central obesity — not just overall weight — is worth naming as a modifiable factor.

The ethnicity-adjusted thresholds already exist. For patients of South or East Asian background, the waist circumference thresholds at which metabolic and cardiovascular risk increases are lower than the standard reference ranges. Cancer risk data at ancestry-adjusted thresholds is less well established, but the principle of not applying European-calibrated cut-offs universally holds.

Verdict: maybe — the visceral fat–cancer link is real and the dataset is large. The new BRI formula itself needs Australian validation before changing practice. Waist circumference measurement, already recommended, captures most of the same information.

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Sources cited

1. Body roundness predicts cancer-related incidence and mortality. Medical Republic, 7 September 2026.
2. Body roundness index and cancer incidence and mortality: UK Biobank analysis. International Journal of Cancer, 22 August 2026.