BMI was invented in 1835 for population statistics, not for assessing your individual health
Adolphe Quetelet, a Belgian mathematician, created his index in 1835 to describe the statistical "average man" of a population, not to assess an individual's health. In 1972, physiologist Ancel Keys named it the "Body Mass Index" and proposed it as a population screening tool. It was never designed to diagnose obesity in a specific person, yet it became the global standard.
WHO BMI categories (standard)
| BMI range | Category |
|---|---|
| < 18.5 | Underweight |
| 18.5 - 24.9 | Normal weight |
| 25.0 - 29.9 | Overweight |
| 30.0 - 34.9 | Obesity class I |
| 35.0 - 39.9 | Obesity class II |
| ≥ 40.0 | Obesity class III (severe) |
Asian-adjusted BMI thresholds, clinically different and WHO-endorsed
A 2004 WHO consultation recommended lower BMI thresholds for East and South Asian populations, because these groups face higher cardiovascular and metabolic risk at lower BMI values than European populations. This is particularly relevant in the UK with its large South Asian community.
| Category | WHO (European/General) | WHO Asian-adjusted |
|---|---|---|
| Normal weight | 18.5 - 24.9 | 18.5 - 22.9 |
| Overweight | 25.0 - 29.9 | 23.0 - 27.4 |
| Obese | ≥ 30.0 | ≥ 27.5 |
UK NICE and NHS England recognise these lower thresholds for clinical assessments in South Asian, Chinese, and other East Asian populations.
When BMI misleads
- Athletes and muscular people: a rugby player at 90 kg / 5'11" has a BMI of 27.8 (overweight) with no excess fat. Muscle is denser than fat.
- Sarcopenic obesity: an older person with "normal" BMI can have very little muscle and high visceral fat, invisible to BMI and one of the most dangerous metabolic patterns. Most common in the 70+ age group.
- Children and adolescents: use BMI-for-age percentile charts (e.g., NHS BMI centile charts), not adult thresholds.
Waist circumference: the recommended complementary measure
| Risk level | Men | Women |
|---|---|---|
| Increased risk | > 94 cm (37 in) | > 80 cm (31.5 in) |
| High risk | > 102 cm (40 in) | > 88 cm (34.5 in) |
Sources: WHO, NHS England, NIH. Asian thresholds per WHO expert consultation 2004. Consult a healthcare provider for individual assessment.