BMI is widely used because it is fast and cheap. It is not perfect. The CDC itself acknowledges several situations where BMI alone gives a misleading picture. Here are the most common ones, and what to do about them.
Athletes and people with high muscle mass
Muscle is denser than fat. A muscular weightlifter can register as "overweight" or even "obese" by BMI while having very low body fat. The classic example: many NFL running backs have BMIs in the obese range despite single-digit body fat.
For athletes, body fat percentage measured via skinfolds, DEXA scan, or hydrostatic weighing gives a far more accurate picture.
Older adults
Bodies change with age — typically losing muscle and gaining fat without weight changing much. A 70-year-old at the same BMI they had at 30 likely has a higher body fat percentage. Some research suggests slightly higher BMIs (25–27) may be protective in older adults, not harmful.
Different ethnicities
Health risk at a given BMI varies by ethnicity. South and East Asian populations tend to develop type 2 diabetes and heart disease at lower BMIs than European populations — the WHO recommends lower screening cutoffs (23 for overweight, 27.5 for obesity) for many Asian groups.
What to use alongside BMI
Waist circumference is the cheapest add-on — a waist over 102 cm (40 in) for men or 88 cm (35 in) for women indicates abdominal obesity, which carries health risks even at "normal" BMI.
Blood pressure, fasting blood sugar, and a basic cholesterol panel from a yearly checkup add far more clinical signal than BMI alone.
Try the free BMI Calculator
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Google Play App StoreBMI is a starting point, not an ending point. Tracking it is still useful — it is just one number among several. Our BMI Calculator makes the starting point trivial; the rest is a conversation with your doctor.
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