“Definition and diagnostic criteria for clinical obesity” (referred to as the “Guideline”), jointly developed by The Lancet Diabetes & Endocrinology Commission, was officially released on January 25, 2025. The Guideline presents a groundbreaking perspective by explicitly defining clinical obesity as a chronic disease and establishing a stratified diagnostic system. It mandates the combined use of anthropometric measurements and clinical assessments, promoting a shift in the diagnosis and treatment model from “body weight management” to comprehensive intervention focused on “body fat metabolism and organ function protection”. Through a systematic interpretation of the core content of the Guideline, including the definition of clinical obesity, key diagnostic criteria, criteria for differential diagnosis, and clinical significance, the document emphasizes the profound impact of the Guideline on the adjustment of medical insurance policies, the standardization of clinical practices, and the protection of patient rights, and aims to enhance the precision diagnosis and stratified management of obesity.