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- Obesity facts
- What is obesity?
- How common is obesity?
- What are the health risks associated with obesity?
- What causes obesity?
- What are other factors associated with obesity?
- How is body fat measured?
- What about weight-for-height tables?
- What is the body mass index (BMI)?
- Does it matter where body fat is located? (Is it worse to be an "apple" or a "pear"?)
- What can be done about obesity?
- What is the role of physical activity and exercise in obesity?
- What is the role of diet in the treatment of obesity?
- What is the role of medication in the treatment of obesity?
- What about herbal fen/phen?
- What about meal substitutes, artificial sweeteners, and over-the-counter (OTC) products?
- What is the role of surgery in the treatment of obesity?
- How can patients choose a safe and successful weight-loss program?
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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.
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 Class||Men 102cm (40 in) or less|
Women 88cm (35 in) or less
|Men > 102cm (40 in)|
Women > 88cm (35 in)
|Normal weight||18.5 - 24.9|
|Overweight||25.0 - 29.9||Increased||High|
|Obesity||30.0 - 34.9||I||High||Very High|
|Obesity||35.0 - 39.9||II||Very High||Very High|
|Extreme Obesity||40.0 +||III||Extremely High||Extremely 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