Under New Criteria for Clinical Obesity, is Metabolic Obesity with Normal Body Weight Finally a Legitimate Disease Phenotype?

The new definition and diagnostic criteria for clinical obesity brought important advances by recognizing the limitations of body mass index (BMI) in identifying excess body fat. In addition, it has evolved in the characterization of obesity as a standalone disease, including a subclassification based on the clinical repercussions directly induced by excess adiposity. In this context, a phenotype marked by reduced gluteofemoral body fat, accumulation of visceral adiposity, and ectopic fat deposition often occurs in people with normal BMI and obesity-related cardiometabolic disorders. Even without characterizing obesity by the current BMI definition, this high-risk profile is recognized as “metabolic obesity” with normal body weight (MONW). This narrative review addresses the characterization, prognostic implications, and pathophysiology of the MONW phenotype in light of the new diagnostic approach to obesity and discusses the strengths and limitations of these new criteria for clinical obesity, with an emphasis on their implications for improving the health of people living with obesity.