Obese, underweight adults at increased risk of all-cause death

Underweight, central obesity, and grade 3 obesity are all associated with a higher risk of death in adults, reveals a study. On the other hand, peripheral fat has an inverse association with mortality.

Some 743 deaths occurred over a median follow-up of 5.83 years. Multivariate analysis revealed that each 10-cm increase in waist circumference (WC; hazard ratio [HR], 1.20, 95 percent confidence interval [CI]), each 0.1-unit increase in waist-to-height ratio (HR, 2.19, 95 percent CI, 1.70–2.83), and each 0.01-unit increase in A Body Shape Index (HR, 1.05, 95 percent CI, 1.03–1.08) correlated with an elevated all-cause mortality risk. 

In contrast, each 1-cm increment in mid-arm circumference contributed to a 13-percent (HR, 0.87, 95 percent CI, 0.83–0.92) lower mortality risk.

Compared with individuals with normal weight (BMI 18.5 to <25.0 kg/m²), those who were underweight (HR, 1.97, 95 percent CI, 1.12–3.45) or had grade 3 obesity (HR, 1.37, 95 percent CI, 1.04–1.81) had an increased mortality risk. After adjusting for WC, however, the effect of grade 3 obesity disappeared. Moreover, the restricted cubic spline (RCS) analyses for BMI shifted to a negative (p<0.01) from a J-shaped association (p<0.05 for nonlinearity test).

In this study, the authors combined NHANES data from 2011 to 2016 with mortality data up to 31 December 2019. A total of 13,728 participants were included after excluding those with cancer at baseline. Cox regression models and RCS analyses were used to examine the link between general obesity, central obesity, and peripheral fat indicators and all-cause mortality risk.