What This Means
This study looked at about 3,200 US adults who reported having had cancer, using national health survey data collected from 2003 to 2018. Researchers tested whether different body measurements were linked to dying from any cause, from cancer, or from heart and blood vessel disease over roughly 8 years of follow-up.
A measure called ABSI (a body shape index, which accounts for waist size relative to height and weight) stood out. People with higher ABSI had a higher risk of dying overall and of dying from cardiovascular disease, but the link with cancer death was not statistically clear. In contrast, BMI and another shape measure (body roundness index) were not independently tied to death risk when treated as continuous measures. Being underweight by BMI was linked to higher overall mortality, and the BMI relationship with death was not a straight line.
This research suggests that where body fat is carried, not just total weight, may matter for survival after cancer, and that BMI alone may miss important information. Because this was an observational study relying on self-reported cancer history, it cannot show cause and effect, and the authors note that more studies are needed to confirm the results.