Clinical obesity and all-cause and cause-specific mortality in UK Biobank

A new epidemiological study led by researchers at the International Agency for Research on Cancer (IARC) and the University of Regensburg, Germany, reveals a clear mortality risk gradient across newly proposed obesity categories, with clinical obesity showing the highest risk for all-cause and cause-specific mortality. The findings confirm that this newer definition of obesity offers more refined risk stratification compared with body mass index (BMI) alone and may also help resolve the obesity paradox.

The researchers used a newly proposed classification from the Lancet Diabetes & Endocrinology Commission that uses objective measures of body size, rather than BMI alone, to identify excess adiposity. The framework further distinguishes between clinical obesity, which is defined as excess adiposity and objective signs and symptoms of obesity-related illness, and preclinical obesity, which is defined as excess adiposity without obesity-related illness.

The new study used data from more than 290 000 adults in UK Biobank, with 16 917 recorded deaths, including 3364 from cardiovascular disease and 8448 from cancer, over an average follow-up of nearly 14 years. Previous mortality risk assessments have predominantly relied on BMI, a simple measure of weight relative to height that does not differentiate fat distribution, body composition, or health status.

The findings indicate that individuals with preclinical obesity already face a significantly elevated mortality risk, even without organ dysfunction. Clinical obesity, which involves both excess adiposity and organ dysfunction, was associated with even higher mortality risks, including cancer-specific mortality.

The implications of this study extend to public health policies and advocate for refining obesity assessment beyond BMI; this will enable better risk stratification and earlier targeted interventions.

This research was funded by World Cancer Research Fund and the French National Cancer Institute (INCa).

Stein MJ, Freisling H, Leitzmann MF
Clinical obesity and all-cause and cause-specific mortality in UK Biobank
JAMA Intern Med. Published online 27 October 2025;
https://doi.org/10.1001/jamainternmed.2025.4978

Read the article