The metabolically healthy obese (MHO) phenotype refers to obese individuals with a favourable metabolic profile. Its prognostic value is unclear and may depend on the health outcome being examined. We examined the association of MHO phenotype with incident cardiovascular disease (CVD) and type 2 diabetes.

Body mass index and metabolic health, assessed using the Adult Treatment Panel-III (ATP-III) criteria, were assessed on 7122 participants (69.7% men) from the Whitehall II study, aged 39–63 years in 1991–93. Incident CVD (coronary heart disease or stroke) and type 2 diabetes were ascertained from medical screenings (every 5 years), hospital data, and registry linkage until 2009. A total of 657 individuals (9.2% of the cohort) were obese and 42.5% of these were classified as MHO in 1991–93. Over the median follow-up of 17.4 years, there were 828 incident cases of CVD and 798 incident cases of type 2 diabetes. Compared with metabolically healthy normal weight individuals, MHO subjects were at increased risk for CVD (HR = 1.97, 95% CI: 1.38–2.80) and type 2 diabetes (3.25, 95% CI: 2.32–4.54). There was excess risk in metabolically unhealthy obese compared with MHO for type 2 diabetes (1.98, 95% CI: 1.39–2.83) but not CVD (1.23, 95% CI: 0.81–1.87). Treating all measures as time varying covariates produced similar findings.

For type 2 diabetes, the MHO phenotype is associated with lower risk than the metabolically unhealthy obese, but for CVD the risk is as elevated in both obesity phenotypes.