Underweight – also called underweight – is more common in Germany than one might suspect. The Federal Statistical Office (Wiesbaden) published figures for the year 2004 on the body measurements of the population by age group. According to these figures, 2.3% of the population in Germany (BMI; body mass index < 18.5) are significantly underweight. This corresponds to approximately 2 million people. Particularly frequently underweight – and in some cases malnourished – are adolescents, who often have eating disorders, and senior citizens. You can calculate whether you are underweight using the BMI – body mass index. BMI is calculated by dividing your body weight in kilograms by the square of your height.
The World Health Organization (WHO) has made a classification of body weight according to BMI:
- Underweight: BMI < 18.5
- Normal weight: BMI 18.5-24.9
- Overweight: BMI 25.0-29.9
- Obesity grade I: BMI 30-34.9
- Obesity grade II: BMI 35-39.9
- Severe obesity grade III: BMI over 40
Age-dependent definition of a desirable BMI according to the National Research Council (USA):
| Age group | Desirable BMI |
| 19-24 years | Minimum 19; maximum 24 |
| 25-34 years | Minimum 20; maximum 25 |
| 35-44 years | Minimum 21; maximum 26 |
| 45-54 years | Minimum 22; maximum 27 |
| 55-64 years | Minimum 23; maximum 28 |
| > = 65 years | Minimum 24; maximum 29 |
People with a body weight below the “desirable BMI” (see information on “minimal”) have a lower life expectancy, since underweight causes the development of numerous secondary diseases, some of which accelerate aging processes.
Thin people with a lot of abdominal fat are particularly at risk for cardiovascular disease. Thin women (BMI < 22.5) with a particularly high abdominal fat percentage (WHR* >0.85) have a 2.4-fold higher mortality (death rate) than women with the same BMI but little abdominal fat (WHR* < 0.77). With a BMI of 22.3 to 25.1, mortality (death rate) was 1.6-fold higher, and with a BMI above 25.2, mortality (death rate) was 1.5-fold higher. * WHI – waist-hip ratio = waist-hip index. You can determine for yourself whether you are a so-called apple or pear type with the “waist-hip ratio” test.
