Body Mass Index (BMI)
A numerical value calculated from weight and height (kg/m²) used to categorise body weight status. BMI is the primary eligibility criterion for obesity pharmacotherapy — GLP-1 receptor agonists for weight management typically require BMI ≥30 or BMI ≥27 with a weight-related comorbidity.
Technical Context
BMI limitations: does not distinguish fat from muscle mass (athletes with high muscle mass may be misclassified as overweight), does not account for fat distribution (visceral vs subcutaneous — waist circumference or waist-to-hip ratio are complementary measures), varies with age/sex/ethnicity (WHO recommends lower BMI thresholds for Asian populations: overweight ≥23, obese ≥27.5), and may underestimate obesity in elderly (due to age-related muscle loss). Despite limitations, BMI remains the standard because of simplicity and extensive epidemiological validation. In GLP-1 RA clinical trials, BMI-based inclusion criteria define the study population: weight management trials require BMI ≥30 (or ≥27 with comorbidity), while diabetes trials may enrol patients across a wide BMI range.