The etiology of obesity is complex and idiosyncratic-with inherited, behavioral, and environmental factors determining the age and rate at which excessive adiposity develops. Moreover, the etiologic status of an obese phenotype (how and when it developed initially) strongly influences both the short-term response to intervention and long-term health trajectories. Nevertheless, current management strategies tend to be 'one-size-fits-all' protocols that fail to anticipate the heterogeneity of response generated by the etiologic status of each individual's phenotype. As a result, the efficacy of current lifestyle approaches varies from ineffective and potentially detrimental, to clinically successful; therefore, we posit that effective management strategies necessitate a personalized approach that incorporates the subtyping of obese phenotypes. Research shows that there are two broad etiologic subtypes: 'acquired' and 'inherited'. Acquired obesity denotes the development of excessive adiposity after puberty-and because the genesis of this subtype is behavioral, it is amenable to interventions based on diet and exercise. Conversely, inherited obesity subsumes all forms of excessive adiposity that are present at birth and develop prior to pubescence (pediatric and childhood). As the inherited phenotype is engendered in utero, this subtype has irreversible structural (anatomic) and physiologic (metabolic) perturbations that are not susceptible to intervention. As such, the most realizable outcome for many individuals with an inherited subtype will be a 'fit but fat' phenotype. Given that etiologic subtype strongly influences the effects of intervention and successful health management, the purpose of this 'perspective' article is to provide a concise overview of the differential development of acquired versus inherited obesity and offer insight into subtype-specific management.
