Metabolically healthy obesity: it is time to consider its dynamic changes

Abstract

Obesity reduces life expectancy, lowers quality of life, and causes numerous cardiometabolic diseases and some cancers. However, the individual risk of developing obesity-associated comorbidities is highly variable and cannot be explained only by body mass index. Observations that some obese people have a low risk for cardiometabolic disorders gave rise to the notion of metabolically healthy obesity (MHO). Despite the lack of a precise definition, MHO is typically identified by normal glucose and lipid metabolism indices, as well as the absence of hypertension. In individuals with MHO, the absence of metabolic abnormalities may minimize the risk of mortality, cardiovascular diseases, chronic kidney disease, dementia, and cancer, compared to metabolically unhealthy individuals with obesity. However, MHO appears to be a temporary phenotype that may not confer permanent benefits to individuals with obesity, further justifying therapeutic efforts to maintain metabolic fitness. In this review, we describe the traits of the MHO phenotype, its changeable nature, and the factors associated with phenotype change. In addition, we discuss the clinical outcomes of the MHO phenotype, particularly focusing on the transition of metabolic health over time and its effect on cardiometabolic disorders. Finally, the clinical importance of maintaining metabolic health is emphasized.