What Is BMI?
Body Mass Index (BMI) is a simple numerical measure of a person's body fat based on their weight and height. It was developed by Belgian mathematician Adolphe Quetelet in the 1830s and is now used worldwide by healthcare professionals as a quick screening tool for weight categories.
BMI Formula
BMI = Weight (kg) ÷ Height² (m²)
Imperial: BMI = 703 × Weight (lbs) ÷ Height² (inches²)
Imperial: BMI = 703 × Weight (lbs) ÷ Height² (inches²)
BMI Categories (WHO Standard)
| BMI Range | Category | Health Risk |
|---|---|---|
| Below 18.5 | Underweight | Increased risk of nutritional deficiency, osteoporosis |
| 18.5 – 24.9 | Normal Weight | Lowest risk — maintain healthy lifestyle |
| 25.0 – 29.9 | Overweight | Moderate risk of heart disease, type 2 diabetes |
| 30.0 – 34.9 | Obese Class I | High risk — consult a healthcare professional |
| 35.0 – 39.9 | Obese Class II | Very high risk |
| 40.0 and above | Obese Class III | Extremely high risk |
Note: BMI is a screening tool, not a diagnostic tool. It does not account for muscle mass, bone density, age, sex, or ethnicity. Always consult your doctor for a complete health assessment.
Limitations of BMI
- BMI can overestimate fat in athletes and bodybuilders
- It can underestimate fat in older people who have lost muscle mass
- Different ethnic groups may have different risk thresholds
- It does not indicate where fat is distributed on the body
How to Improve Your BMI
If your BMI falls outside the healthy range, lifestyle changes can make a significant difference. A combination of regular physical activity (at least 150 minutes of moderate exercise per week) and a balanced diet rich in fruits, vegetables, lean proteins, and whole grains is the most effective approach.