WHO International BMI Classification
The World Health Organization established the following BMI classification for adults (aged 18+) as an international standard. These cut-offs have been adopted by health ministries and medical institutions in over 190 countries as the basis for obesity surveillance, policy, and clinical guidelines.
| BMI (kg/m²) | Classification | Population Prevalence |
|---|---|---|
| < 16.0 | Severely Underweight | ~1% globally |
| 16.0 – 16.9 | Moderately Underweight | ~1.5% |
| 17.0 – 18.4 | Mildly Underweight | ~4% |
| 18.5 – 24.9 | Normal / Healthy Weight ✓ | ~38% |
| 25.0 – 29.9 | Overweight (Pre-obese) | ~38% |
| 30.0 – 34.9 | Obese Class I | ~12% |
| 35.0 – 39.9 | Obese Class II | ~5% |
| ≥ 40.0 | Obese Class III | ~3% |
WHO Recommended BMI Cut-offs for Asian Populations
Following a WHO Expert Consultation in 2004, additional action points were proposed for Asian populations. Research consistently shows that people of Asian descent develop metabolic complications at lower BMI values than the international classification suggests:
| BMI (kg/m²) | International Classification | Asian Action Points |
|---|---|---|
| < 18.5 | Underweight | Underweight |
| 18.5 – 22.9 | Normal Weight | Normal Weight |
| 23.0 – 24.9 | Normal Weight | ⚠️ At Risk / Increased Risk |
| 25.0 – 27.4 | Overweight | Moderately Obese |
| ≥ 27.5 | Obese Class I | Severely Obese |
Countries including Japan, Singapore, China, South Korea, and India have adopted these modified thresholds in their national health guidelines.
WHO Waist Circumference Guidelines
The WHO also provides guidance on waist circumference as a complementary indicator of abdominal obesity and associated health risks. Waist circumference is often considered more predictive of metabolic risk than BMI alone:
| Sex | Increased Risk | High Risk |
|---|---|---|
| Men | ≥ 94 cm (37") | ≥ 102 cm (40") |
| Women | ≥ 80 cm (31.5") | ≥ 88 cm (34.5") |
For Asian populations, lower thresholds are recommended: increased risk starts at ≥ 90 cm (35.5") for men and ≥ 80 cm (31.5") for women.
Waist-to-Height Ratio
A simple and powerful screening tool: keep your waist circumference below half your height. This single rule has been shown to predict cardiovascular risk better than BMI in several population studies. For example, a person who is 175 cm tall should aim for a waist circumference below 87.5 cm.
WHO Global Action Plan on Obesity
The WHO's Global Action Plan for the Prevention and Control of Noncommunicable Diseases includes specific targets related to obesity and weight management. Key goals include halting the rise in obesity and diabetes by 2030, and reducing premature mortality from cardiovascular disease, cancer, diabetes, and chronic respiratory diseases by one-third.
WHO Recommendations for a Healthy Weight
The WHO provides the following evidence-based recommendations for maintaining a healthy weight:
- Physical activity: Adults should accumulate at least 150–300 minutes of moderate-intensity aerobic physical activity per week, plus muscle-strengthening activities on 2+ days per week
- Diet: Consume at least 400g (5 portions) of fruits and vegetables per day; limit free sugars to less than 10% of total energy intake; limit fat intake to less than 30% of total energy; limit sodium intake to less than 5g per day
- Limit ultra-processed foods: High in energy, sugar, salt, and fat while being low in fiber and micronutrients
- Eliminate trans fats: Industrially-produced trans fatty acids (iTFAs) should be eliminated from the food supply
- Alcohol: No safe level of alcohol consumption for health; reducing intake has direct metabolic benefits
WHO Targets for Healthy Weight Management
| Target Metric | WHO Goal |
|---|---|
| Body weight | BMI 18.5–24.9 kg/m² |
| Waist (men) | < 94 cm |
| Waist (women) | < 80 cm |
| Blood pressure | < 130/80 mmHg |
| Fasting blood glucose | < 5.6 mmol/L (100 mg/dL) |
| LDL cholesterol | < 2.6 mmol/L (100 mg/dL) |
| Physical activity | ≥ 150 min moderate/week |
Global Obesity Statistics (WHO 2024)
- Worldwide obesity has more than tripled since 1975
- In 2022, over 2.5 billion adults (18+) were overweight, of which over 890 million were obese
- The global prevalence of obesity among adults more than doubled between 1990 and 2022
- Obesity rates are highest in the Americas, Europe, and Eastern Mediterranean regions
- Obesity is now more common than underweight in most world regions except Sub-Saharan Africa and Asia
- The economic burden of obesity and overweight costs the global economy an estimated $2 trillion annually