Objective: The possibility that a subset of persons who are obese may be metabolically healthy—referred to as the ‘metabolically healthy obese’ (MHO) phenotype—has attracted attention recently. However, few studies have followed individuals with MHO or other obesity phenotypes over time to assess change in their metabolic profiles. The aim of the present study was to examine transitions over a 6-year period among different states defined simultaneously by body mass index (BMI) and the presence/absence of the metabolic syndrome (MetS).
Methods: We used repeated measurements available for a subcohort of participants enrolled in the Women’s Health Initiative (N=3512) and followed for an average of 6 years to examine the frequency of different metabolic obesity phenotypes at baseline, the 6-year transition probabilities to other states and predictors of the risk of different transitions. Six phenotypes were defined by cross-tabulating BMI (18.5–<25.0, 25.0–<30.0, 30.0 kg m−2) by MetS (yes, no). A continuous-time Markov model was used to estimate 6-year transition probabilities from one state to another.
Results: Over the 6 years of follow-up, one-third of women with the healthy obese phenotype transitioned to the metabolically unhealthy obese (MUO) phenotype. Overall, there was a marked tendency toward increased metabolic deterioration with increasing BMI and toward metabolic improvement with lower BMI. Among MHO women, the 6-year probability of becoming MUO was 34%, whereas among unhealthy normal-weight women, the probability of ‘regressing’ to the metabolically healthy normal-weight phenotype was 52%.
Conclusions: The present study demonstrated substantial change in metabolic obesity phenotypes over a 6-year period. There was a marked tendency toward metabolic deterioration with greater BMI and toward metabolic improvement with lower BMI.