The Metabolically Healthy Obese Phenotype: The Atypical Normal or Disorder in Progress?

Abstract

The Metabolically Healthy Obese (MHO) is a unique phenotype of obesity in which individuals match the operational definition of obesity but do not display metabolic complications. Given this attribute, MHO has gained rapid interest in the field of adiposity research over the recent decades. Whether the MHO phenotype is apparently free of cardiometabolic abnormalities or simply a transient state of the metabolically unhealthy obese (MUO) remains controversial, but this ambiguous phenotype deserve clinical merit as it may serve as a missing conduit to further understand the complex nature of human obesity. Furthermore, shedding light in the still controversial MHO may help further research in in terms of customizing interventions aimed at decreasing the cardiometabolic risks associated with the MUO phenotypes and/or maintaining the “normalcy” of MHO over time. In this review, we aim to promote and update existing knowledge on the different metabolic health phenotypes of obesity as gathered from recent literature, primarily for the obese population and for primary care physicians who are first in-line in encountering these phenotypes. This may also help healthcare providers to have better awareness in identifying which obese phenotypes can actually benefit from weight loss programs. In light of available evidence, more longitudinal and translational studies are still needed to reach a universal definition of MHO.