The association between all-cause mortality and BMI created a U-shaped curve with a broad base (P-nonlinearity <0.001). The “nadir of the curve for BMI and mortality was between 24.0 and 30.9, with the lowest risk being between 27.0 and 27.9 (HR 0.90, 95% CI 0.88-0.92),” wrote Caryl A. Nowson, PhD, of Deakin University in Melbourne, Australia, and her co-authors, in the American Journal of Clinical Nutrition.

They said that mortality risk did not increase with excess weight in this population until BMI was ≥33 (HR 1.08 for BMI of 33.0-33.9, 95% CI 1.00-1.15).

Risk of mortality was highest at a BMI lower than 23, the authors said. Using a BMI of 23.0 to 23.9 as the reference, there was a 12% greater risk of mortality for those with a BMI in the range of 21.0-21.9 (HR 1.12, 95% CI 1.10-1.13) and a 19% greater risk for those with a BMI in the range of 20.0-20.9 (HR 1.19, 95% CI 1.17-1.22), the authors said.

via Higher BMI May Be Better for Older Adults.

BMI and all-cause mortality in older adults: a meta-analysis.