Mediterranean diet and mortality risk in metabolically healthy obese and metabolically unhealthy obese phenotypes

BACKGROUND: The Mediterranean diet has been consistently associated with reduced mortality risk. Few prospective studies have examined whether the benefits from a Mediterranean diet are equally shared by obese individuals with varying metabolic health. OBJECTIVE: The objective of this study was to investigate the association between Mediterranean diet, metabolic phenotypes and mortality risk in a representative obese US population. METHODS: Data from 1739 adults aged 20-88 years were analyzed from participants of the National Health and Nutrition Examination Survey III, 1988-1994 followed up for deaths until 31 December 2011 in a prospective cohort analysis. Mediterranean Diet Scores (MDS) were created to assess the adherence to Mediterranean diet. Participants were classified as metabolically healthy obese (MHO) phenotype (0 or 1 metabolic abnormality) or metabolically unhealthy obese (MUO) phenotype (two or more metabolic abnormalities), based on high glucose, insulin resistance, blood pressure, triglycerides, C-reactive protein and low high-density lipoprotein cholesterol. RESULTS: The MHO phenotype (n = 598) was observed in 34.8% (s.e., 1.7%) of those who were obese (mean body mass index was 33.4 and 34.8 in MHO and MUO phenotypes, respectively). During a median follow-up of 18.5 years, there were 77 (12.9%) and 309 (27.1%) deaths in MHO and MUO individuals, respectively. In MHO individuals, the multivariable-adjusted hazard ratio (HR) of all-cause mortality in the highest tertile compared with the first tertile of MDS was 0.44 (95% confidence interval (CI), 0.26-0.75; P for trend < 0.001), after adjustment for potential confounders. A five-point (1 s.d.) increment in the adherence to MDS was associated with a 41% reduction in the risk of all-cause mortality (HR, 0.59; 95% CI, 0.37-0.94). Similar findings were obtained when we restricted our analyses to those with or without prevalent diabetes mellitus and hypertension. We did not observe mortality risk reduction in either individuals with MUO phenotype or all obese participants combined. CONCLUSIONS: Adherence to a Mediterranean dietary pattern appears to reduce mortality in the MHO phenotype, but not among the MUO phenotype in an obese population.