Medical Book

LANGUAGE
English Español 中文 Українська
Search

Showing results for: Array

    Medical Book

    LANG
    English Español 中文 Українська
    BMI
    Home > Parameters

    BMI

    Body mass index: WHO categories, Asian cut-offs, limitations and health risks of low and high BMI.

    Body mass index (BMI) is body weight in kilograms divided by the square of height in metres. It is the standard screening measure for underweight, overweight and obesity in adults. BMI is simple and correlates with body fat at the population level, but it does not distinguish fat from muscle and does not show where fat is stored. Obesity raises the risk of type 2 diabetes, hypertension, coronary heart disease, stroke, fatty liver, sleep apnoea, osteoarthritis and several cancers.

    AnthropometryObesityNutrition
    Formulaweight (kg) / height² (m²)
    Normal (WHO)18.5–24.9 kg/m²
    Overweight25.0–29.9 kg/m²
    Obesity≥ 30 kg/m²
    WHO adult BMI classification: underweight below 18.5, normal 18.5 to 24.9, overweight 25 to 29.9, obesity class I 30 to 34.9, class II 35 to 39.9, class III 40 and above Body mass index (kg/m²) Underweight below 18.5 18.5 Normal 18.5–24.9 25 Overweight 25–29.9 30 Obesity I 30–34.9 35 Obesity II 35–39.9 40 Obesity III ≥ 40
    Figure 1. WHO classification of BMI in adults. For Asian populations, WHO suggests additional public-health action points at 23 and 27.5 kg/m².

    Example

    BMI = 80 kg / (1.75 m)² = 80 / 3.06 ≈ 26.1 kg/m² (overweight)

    Limitations

    • Muscular people (athletes) may have a high BMI without excess fat; older people may have a "normal" BMI with little muscle and much fat
    • At the same BMI, people of Asian origin tend to have more body fat and higher diabetes risk, so lower action points (23 and 27.5 kg/m²) are used in many Asian countries
    • BMI does not show fat distribution. Waist circumference adds information: abdominal (visceral) fat carries the greatest metabolic risk
    • Adult cut-offs do not apply to children, adolescents or pregnant women; children use age- and sex-specific percentiles

    Health risks

    Low BMI

    Malnutrition, eating disorders, chronic disease (cancer, tuberculosis, hyperthyroidism, malabsorption). Risks: weakened immunity, osteoporosis, anaemia, infertility, poor wound healing.

    High BMI

    Insulin resistance and type 2 diabetes, hypertension, dyslipidaemia, coronary heart disease, heart failure, atrial fibrillation, fatty liver, sleep apnoea, joint disease, some cancers.

    What to do

    Even a 5–10% weight loss improves blood pressure, glucose and lipids. Unintended weight loss of more than about 5% in 6–12 months should be investigated by a doctor.

    References

    1. World Health Organization. Obesity: preventing and managing the global epidemic. Report of a WHO consultation. WHO Technical Report Series 894. Geneva: WHO; 2000.
    2. WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163. doi:10.1016/S0140-6736(03)15268-3

    This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.

    Published on 1 June 2019