Human bodies rank along the index from around 15 (near starvation) to over 40 (morbidly obese). The exact index values used to determine weight categories vary from authority to
authority, but in general a BMI less than 18.5 is underweight and may indicate malnutrition, an eating disorder, or other health problems, while a BMI greater than 25 is
overweight and above 30 is considered obese. These range boundaries apply to adults over 20 years of age.
| BMI |
Rating |
Waist Size |
| |
≤ 40 in. (men) or 35 in. (women) |
≥ 40 in. (men) or 35 in. (women) |
| 18.5 or less |
Underweight |
-- |
N/A |
| 18.5-24.9 |
Normal Weight |
-- |
N/A |
| 25.0-29.9 |
Overweight |
Increased |
High |
| 30.0-34.9 |
Obese |
High |
Very High |
| 35.0-39.9 |
Obese |
Very High |
Very High |
| 40 or greater |
Extremely Obese |
Extremely High |
Extremely High |
BMI is equal to or less than 18.5 (Underweight):
A lean BMI can indicate that your weight maybe too low. You should consult your physician to determine if you should gain weight, as low body mass can decrease your body's
immune system, which could lead to illness.
BMI is between 18.5 and 24.9 (Normal):
People whose BMI is within 18.5 to 24.9 possess the ideal amount of body weight, associated with living longest, the lowest incidence of serious illness, as well as being
perceived as more physically attractive people than persons with BMI in higher or lower ranges.
BMI is between 25 and 29.9 (Overweight):
Persons falling in this BMI range are considered overweight and would benefit from finding healthy ways to lower their weight, such as diet and exercise. Individuals who
fall in this range are at increased risk for a variety of illnesses.
BMI is over 30 (Obese):
Individuals with a BMI over 30 are in a physically unhealthy condition, which puts them at risk for serious illnesses such as heart disease, diabetes, high blood pressure,
gall bladder disease, and some cancers. These persons would benefit greatly by modifying their lifestyle.
Body mass index (BMI) or Quetelet Index is a statistical measure of the weight of a person scaled according to height. It was invented between 1830 and 1850 by the Belgian
polymath, Adolphe Quetelet during the course of developing "social physics".
Body Mass Index (BMI) is one of the most accurate ways to determine when extra pounds translate into health risks. BMI is a measure which takes into account a person's weight
and height to gauge total body fat in adults. Someone with a BMI of 26 to 27 is about 20 percent overweight, which is generally believed to carry moderate health risks. A BMI
of 30 and higher is considered obese. The higher the BMI, the greater the risk of developing additional health problems.
The BMI has become controversial because many people, including physicians, have come to rely on it for medical diagnosis - but that has never been the BMI's purpose. It is
meant to be used as a simple means of classifying sedentary (physically inactive) individuals with an average (mesomorphic) body composition. For these individuals, the current
value settings are as follows: a BMI of 25 may indicate optimal weight; a BMI lower than 25 suggests the person is underweight while a number above 25 may indicate the person
is overweight; a BMI below 20 may indicate the person has an eating disorder; a number above 30 suggests the person is obese (over 40, morbidly obese).
The BMI is meant to broadly categorize populations for purely statistical purposes. As noted, its accuracy in relation to actual levels of body fat is easily distorted by such
factors as fitness level, muscle mass, bone structure, sex, and ethnicity. People who are endomorphic or ectomorphic tend to have higher BMI numbers than people who are
mesomorphic, because they have greater bone mass and greater muscle mass, respectively, than do mesomorphic individuals.
