How Are Overweight and
Obesity Defined?
The body mass index (BMI) is the most popular tool for
defining what is healthy weight, overweight and obesity today.
The BMI is calculated by multiplying weight in pounds by 703 and
then dividing by the height in inches. Then divide that result
by your height in inches once more. Clinical Guidelines on the
Identification, Evaluation and Treatment of Overweight and
Obesity in Adults, developed by the National Heart, Lung and
Blood Institute, recommend the following classifications for
BMI:
 | Underweight - BMI less than 18.5
|
| Normal weight - BMI 18.5 to 24.9
|
| Overweight - BMI 25 to 29.9
|
| Obesity - BMI 30 to 34.9 (Class 1)
|
| Obesity - BMI 35 to 39.9 (Class 2)
|
| Extreme Obesity - BMI greater than 40 (Class 3) |
BMI does not actually measure body fat, but generally
correlates well with the degree of obesity. For example, a
person who is 5 feet, 7 inches tall and weighs 150 pounds would
have a BMI of 23, well out of the range of obesity. A person of
the same height and weighing 200 pounds would have a BMI of 31
and would be considered obese. BMI charts are widely available.
Often, a 10 to 15% reduction in an obese person’s body weight
can bring about a significant reduction in the person’s health
risk from obesity. This “healthy” weight loss does not always
equate with a person’s “cosmetic” weight loss goals.
