Abstract

Objective: The clinical relevance of the metabolically normal but obese phenotype for mortality risk is unclear. This study examines the risk for all-cause mortality in metabolically normal and abnormal obese (MNOB and MAOB).

Research Design and Methods: The sample included 6,011 men and women from NHANES III with public-access mortality data linkage (follow-up = 8.7±0.2 years; 292 deaths). MA was defined as insulin resistance (IR) or ≥2 metabolic syndrome (MetS) criteria (excluding waist).

Results: Thirty percent of obese were IR, and 38.4% had ≥2 MetS factors, whereas only 6.0% (or 1.6% of the whole population) were free from both IR and all MetS factors. By MetS factors or IR alone, MNOB [HR_MetS=2.80(1.18-6.65); HR_IR=2.58(1.00-6.65)] and MAOB [HR_MetS=2.74(1.46-5.15); HR_IR=3.09(1.55-6.15)] had similar elevations in mortality risk compared to MNNW.

Conclusions: Although a rare phenotype, obesity even in the absence of overt metabolic aberrations is associated with increased all-cause mortality risk.