The increasing prevalence of obesity and associated cardiovascular disease (CVD) make it important for health interventions to target those at greatest risk. This risk for overweight and obese people categorized as ‘metabolically healthy’ remains contentious.1
A systematic review and meta-analysis was conducted according to MOOSE guidelines.2 Medline, EMBASE, SCOPUS and Cochrane, were searched and high-moderate quality studies published to 30thJune 2018 included. Metabolic health was defined using NCEP-ATP III,3 IDF criteria,4 or absence of insulin resistance.5 A random-effect model was used to pool relative risk for association of BMI-metabolic health and CVD. Heterogeneity was assessed using subgroup analysis and meta-regression. Publication bias was investigated using Funnel plots and Egger’s test.
Twenty-three prospective studies were identified, and twenty studies of moderate-high quality were included. Increased CVD risk was identified in metabolically healthy overweight (RR=1.33,CI:1.22-1.45,I-squared=90.3%,n=20) and obese (RR=1.52,CI:1.34-1.74,I-squared=87.4%,n=20) groups, when compared to a metabolically healthy normal-weight reference group. The subgroup of studies including both male and female participants showed a similar pooled effect size for overweight (RR=1.31,CI:1.19-1.45,I-squared 91.5%,n=16) and obese (RR:1.49,CI:1.28-1.73,I-squared=88.8%,n=16) groups, with the highest CVD risk evident in an obese metabolically unhealthy group (RR=2.57,CI:1.79-3.70,I=99.4%,n=16). The CVD risk in the metabolically health overweight and obese participants was independent of the quantity of metabolic risk factors present or the specific criteria used to define metabolic syndrome. Subgroup analysis showed that heterogeneity became insignificant when only high quality studies were analysed.
This study concurs with initial reviews that suggested increased cardiovascular risk in metabolically healthy obese participants.6-8 The risk of future CVD is increased in overweight and obese participants despite favourable metabolic parameters at initial assessment. The overall risk of cardiovascular events was still increased by 33% in overweight and 52% in obese participants who had an absence of any metabolic risk factors. The term ‘metabolically healthy obesity’ may be a misnomer.