Body mass index (BMI) and waist circumference measure different things. BMI compares weight with height, while waist circumference adds information about where body fat is distributed. Neither number is a diagnosis; a health professional should interpret them alongside individual health information.
How to calculate BMI
Divide weight in kilograms by height in metres squared. For example: 60 ÷ (1.60 × 1.60) = BMI 23.4 kg/m². For adults, the World Health Organization uses BMI of 25 or above as the international threshold for overweight and 30 or above for obesity. These are population screening thresholds, not an individual diagnosis.
Why BMI does not describe health by itself
BMI does not distinguish fat from muscle or show where fat is carried. The relationship between BMI, body fat and health risk can differ between populations. Children and adolescents need age- and sex-specific assessment; adult cutoffs should not be applied directly.
What waist circumference adds—and how it is measured
WHO discusses waist circumference alongside BMI when studying noncommunicable disease risk. Its standard method measures midway between the lower edge of the last palpable rib and the top of the hip bone. Keep the tape level and snug without compressing the skin, then measure after a normal exhalation. Measurement can vary, so a trained professional can help when the result is being used in health care.
There is no single waist threshold that fits everyone. Interpretation depends on measurement method, sex, age and population. A clinician may also consider medical history, blood pressure, test results and other health factors. If your weight changes rapidly, you have unusual symptoms or you are concerned, consult a health professional.
Frequently asked questions
Does a high BMI mean that someone is definitely ill?
No. BMI is a screening measure and must be interpreted with other health information.
Can children use adult BMI thresholds?
No. Children need an age- and sex-aware assessment with support from an appropriate health professional.
Sources
- WHO: Obesity and overweight
- WHO: BMI limitations across populations
- WHO: Waist circumference and waist-to-hip ratio
Original video
Obesity: A Health Threat, Part 1 with Dr. Amp — BDMS Wellness Club