Body mass index (BMI) is an anthropometric standard measure defining the body composition of men and women. Initially it was used to measure obesity in developed countries, but it is now applied to underweight and overweight adults throughout the world. BMI provides a simple, convenient and relatively inexpensive indicator for assessing whether a person is taking in too little or too much energy. However, BMI is a crude measure of nutritional status, and additional information is needed to determine a person's health status. In addition, the values may have to be adapted for specific groups of adults, such as adolescents, pregnant women, and the elderly.
BMI is calculated by as: BMI = body weight (kg) / height2 (m2). The healthy range of BMI for adults, as recommended by FAO, the WHO, and the International Dietary Energy Consultative Group, is considered 18.5-25. Figures 4 and 5 show a range of BMI scores from severely underweight (< 16) to severely obese (> 40) adult men and women. The risk of health problems is greater for people with BMI at either end of the spectrum than for those in the middle range (18.5-25). Nonetheless, the cut-off points of 18.5, defining underweight, and 25, defining overweight, are not universally accepted. Some researchers believe that cut-off points based on country-specific reference groups should be established to reflect differences in height and muscle mass. Concerns about the universal applicability of the BMI should be kept in mind when interpreting the prevalence of underweight and overweight people in selected countries and groups.
Severely Moderately Mildly Healthy Mildly Moderately Severely underweight underweight underweight range overweight overweight obese
Physical symptoms of healthy BMI levels
- Thin for height
- Inadequate energy for normal activity
- Susceptible to disease
- Poor maternal and infant health
- Health problems caused by macro- and micronutrient deficiencies
Normal active life Less risk of illness ■ No nutrition-related health problems given a well-balanced diet
- Sedentary lifestyle
- Cardiovascular diseases
- Risk of certain cancers
- Health problems caused by macro- and micronutrient imbalances
Fig.4. The body mass index (BMI) in adults under normal and clinical conditions
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