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What BMI means
| BMI | Adult category (WHO/CDC) |
|---|---|
| Below 18.5 | Underweight |
| 18.5–24.9 | Healthy weight |
| 25–29.9 | Overweight |
| 30+ | Obesity |
BMI = weight (kg) ÷ height (m)². It is quick and free, but it does not measure body fat directly: muscular people can score high. Pair it with waist size. For South Asian, Chinese and some other populations, NICE uses lower action points (23 and 27.5).
Do this today
Calculate your BMI, then measure your waist. Write both down with today’s date and check again in 4 weeks.
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Check yourself: 2 quick questions
Perfect score = combo bonus. Each question returns in your spaced-repetition review.
Questions people ask
Is BMI accurate?
It is a useful population screening tool but can misclassify muscular people and does not show where fat is stored.
What BMI is healthy?
18.5–24.9 for most adults, with lower cut-offs suggested for some ethnic groups.
Sources
- CDC. Adult BMI calculator and categories. Checked October 23, 2026.
- WHO. Obesity and overweight fact sheet. Checked October 23, 2026.
- NICE. Overweight and obesity management (NG246). Checked October 23, 2026.
Education only. Not medical advice. Confirm with your clinician.