Obesity

  • Medical Author:
    Jerry R. Balentine, DO, FACEP

    Dr. Balentine received his undergraduate degree from McDaniel College in Westminster, Maryland. He attended medical school at the Philadelphia College of Osteopathic Medicine graduating in1983. He completed his internship at St. Joseph's Hospital in Philadelphia and his Emergency Medicine residency at Lincoln Medical and Mental Health Center in the Bronx, where he served as chief resident.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What about weight-for-height tables?

Measuring a person's body fat percentage can be difficult, so other methods are often relied upon to diagnose obesity. Two widely used methods are weight-for-height tables and body mass index (BMI). While both measurements have their limitations, they are reasonable indicators that someone may have a weight problem. The calculations are easy, and no special equipment is required.

Most people are familiar with weight-for-height tables. Although such tables have existed for a long time, in 1943, the Metropolitan Life Insurance Company introduced their table based on policyholders' data to relate weight to disease and mortality. Doctors and nurses (and many others) have used these tables for decades to determine if someone is overweight. The tables usually have a range of acceptable weights for a person of a given height.

One problem with using weight-for-height tables is that doctors disagree over which is the best table to use. Several versions are available. Many have different weight ranges, and some tables account for a person's frame size, age and sex, while other tables do not.

A significant limitation of all weight-for-height tables is that they do not distinguish between excess fat and muscle. A very muscular person may be classified as obese, according to the tables, when he or she in fact is not.

What is the body mass index (BMI)?

The body mass index (BMI) is a now the measurement of choice for many physicians and researchers studying obesity.

The BMI uses a mathematical formula that accounts for both a person's weight and height.

The BMI measurement, however, poses some of the same problems as the weight-for-height tables. Not everyone agrees on the cutoff points for "healthy" versus "unhealthy" BMI ranges. BMI also does not provide information on a person's percentage of body fat. However, like the weight-for-height table, BMI is a useful general guideline and is a good estimator of body fat for most adults 19 and 70 years of age. However, it may not be an accurate measurement of body fat for bodybuilders, certain athletes, and pregnant women.

The BMI equals a person's weight in kilograms divided by height in meters squared (BMI = kg/m2). To calculate the BMI using pounds, divide the weight in pounds by the height in inches squared and multiply the result by 703.

It is important to understand what "healthy weight" means. Healthy weight is defined as a body mass index (BMI) equal to or greater than 19 and less than 25 among all people 20 years of age or over. Generally, obesity is defined as a body mass index (BMI) equal to or greater than 30, which approximates 30 pounds of excess weight.

The World Health Organization uses a classification system using the BMI to define overweight and obesity.

  • A BMI of 25 to 29.9 is defined as a "pre-obese."
  • A BMI of 30 to 34.99 is defined as "obese class I."
  • A BMI of 35 to 39.99 is defined as "obese class II."
  • A BMI of or greater than 40.00 is defined as "obese class III."

The table below has already done the math and metric conversions. To use the table, find the appropriate height in the left-hand column. Move across the row to the given weight. The number at the top of the column is the BMI for that height and weight.

BMI
(kg/m2)
1920212223242526272829303540
Height
(in.)
Weight (lb.)
589196100105110115119124129134138143167191
599499104109114119124128133138143148173198
6097102107112118123128133138143148153179204
61100106111116122127132137143148153158185211
62104109115120126131136142147153158164191218
63107113118124130135141146152158163169197225
64110116122128134140145151157163169174204232
65114120126132138144150156162168174180210240
66118124130136142148155161167173179186216247
67121127134140146153159166172178185191223255
68125131138144151158164171177184190197230262
69128135142149155162169176182189196203236270
70132139146153160167174181188195202207243278
71136143150157165172179186193200208215250286
72140147154162169177184191199206213221258294
73144151159166174182189197204212219227265302
74148155163171179186194202210218225233272311
75152160168176184192200208216224232240279319
76156164172180189197205213221230238246287328

Table Courtesy of the National Institutes of Health

Below is a table identifying the risk of associated disease according to BMI and waist size.

Disease Risk* Relative to Normal Weight and Waist Circumference
BMI (kg/m2)Obesity ClassMen 102cm (40 in) or less
Women 88cm (35 in) or less
Men > 102cm (40 in)
Women > 88cm (35 in)
Underweight< 18.5
Normal weight18.5 - 24.9
Overweight25.0 - 29.9IncreasedHigh
Obesity30.0 - 34.9IHighVery High
Obesity35.0 - 39.9IIVery HighVery High
Extreme Obesity40.0 +IIIExtremely HighExtremely High

* Disease risk for type 2 diabetes, hypertension, and CVD.

+ Increased waist circumference can also be a marker for increased risk even in persons of normal weight.

Table Courtesy of the National Institutes of Health

Medically Reviewed by a Doctor on 12/9/2015

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