Metabolically healthy obesity and the risk of all-cause and cardiovascular disease mortality in a Korean population: a prospective cohort study

Objectives This study aimed to examine the association between metabolically healthy obesity and all-cause and cardiovascular disease (CVD) mortality in a Korean population. Design A prospective study. Setting This study used data from the Korean Genome and Epidemiology Study. Participants A total of 140 137 participants were followed up over a median period of 9.2 years. Participants were categorised into four groups according to obesity (obese: body mass index >= 25 kg/m(2) or non-obese) and metabolic health (metabolically unhealthy: two or more metabolic abnormalities or metabolically healthy). Primary and secondary outcome measures All-cause and CVD mortality of the participants until 31 December 2018 were ascertained by the National Health Insurance Service of beneficiary status of Korea. Results Metabolically unhealthy non-obese participants were at elevated risk of all-cause mortality (HR, 1.12; 95% CI, 1.04 to 1.21; p=0.0019) and CVD mortality (HR, 1.39; 95% CI, 1.17 to 1.65; p=0.0002), particularly mortality from ischaemic heart disease (IHD) (HR, 1.54; 95% CI, 1.10 to 2.14; p=0.0116) compared with metabolically healthy non-obese participants. Surprisingly, metabolically healthy obese participants were at reduced risk of all-cause mortality (HR, 0.89; 95% CI, 0.81 to 0.98; p=0.0197). Metabolically unhealthy obese participants were at elevated risk of CVD mortality (HR, 1.51; 95% CI, 1.26 to 1.81; p<0.0001) and IHD mortality (HR, 1.88; 95% CI, 1.35 to 2.63; p=0.0002) compared with metabolically healthy non-obese participants. Conclusions In a Korean population, metabolically healthy obese participants had reduced risk of all-cause mortality compared with their non-obese counterparts, whereas metabolically unhealthy participants had elevated risk of CVD mortality, in particular mortality from IHD regardless of obesity.