Body-mass index (BMI) shows the relationship between height and weight. The normal range is between 18.5 and 24.9. Values below 18.5 indicate underweight, and values below 14.5 are life-threatening.
Even though the BMI is not the ultimate parameter of health, it is a good indicator of extremes. Severe overweight can also have life-threatening effects, albeit less acute. A BMI of more than 30 indicates severe overweight; this should be reduced.