BMI (Body Mass Index)

A weight-to-height ratio used as a screening tool to categorize underweight, normal weight, overweight, and obesity in adults.

Body Mass Index (BMI) is calculated as weight in kilograms divided by height in meters squared (kg/m²). It is a screening tool, not a diagnostic measure — BMI does not directly measure body fat percentage, muscle mass, or metabolic health. For adults age 20+, the CDC categorizes BMI as: underweight (<18.5), normal weight (18.5–24.9), overweight (25.0–29.9), obesity Class 1 (30.0–34.9), Class 2 (35.0–39.9), and Class 3 / severe obesity (≥40). FDA-approved GLP-1 medications for chronic weight management (Wegovy, Zepbound) are indicated for adults with a BMI ≥30, OR a BMI ≥27 with at least one weight-related comorbidity (such as type 2 diabetes, hypertension, dyslipidemia, or obstructive sleep apnea). BMI cutoffs are used as eligibility criteria but individual provider assessment determines clinical appropriateness. BMI has known limitations — it can misclassify highly muscular individuals as overweight and underestimate body fat in older adults — which is why providers consider BMI alongside other clinical factors.

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This glossary is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your individual health.