Amount and quality of research validating its effectiveness

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BMI and WHR as Health Indicators

Anstadt, Mark L.

Part I.

“Are doctors now using BMI (Body Mass Index) as an indicator of

obesity, and why... is this becoming ‘standard’...”

Body Mass Index (BMI) has gained international acceptance as a standard for recognition and classification of overweight and obesity. It is used by Nurses, Registered dieticians, Nurses, Nurse Practitioners, Physician’s assistants, Doctors, and other health care professionals as an initial screen to identify individuals at risk for problems related to being overweight or underweight.1

Calculating BMI: 2

|BMI = ( |            Weight in Pounds              |) x 703 |

| |(Height in inches) x (Height in inches) | |

OR

|BMI = |            Weight in Kilograms              |

| |(Height in Meters) x (Height in Meters) |

Online BMI calculator:

The BMI Categories for adult men and women are: 3

<18.5 = Underweight

18.5-24.9 = Normal

25-29.9 = Overweight

30-34.9 = Class I Obesity

35-39.9 = Class II Obesity

40+ = Class III / Extreme obesity

These BMI categories published by the NIH and closely reflect the WHO’s recommended BMI classifications. 1

*Note: CDC’s BMI-for-age growth charts should be used for children. 4

Its Merits:

1. Extensive research validates its use in predicting increased risk of death and disease associated with being overweight. It has been validated for all adults of both sexes and multiple ethnic backgrounds. 5

For example – it has been determined that persons with a BMI at or over 30 have about twice the risk of developing high blood pressure as those with a BMI under 25. 3

2. It is an internationally accepted standard tool. This allows all Health professionals to “speak the same language” regarding body weight. Standard tools are necessary for the creation and implementation of programs to identify and treat those at risk for weight related health problems. 1

For example, the National Institutes of Health could not justify spending money to address the problem of obesity in America if there was not a widely accepted definition of obesity.

Its Shortcomings:

There is almost complete consensus regarding the usefulness of BMI as a screening tool. The only exception to this is for individuals who have very high muscle mass (body builders) or have recently lost muscle mass (as with advanced cancer or starvation). For these individuals, direct measuring of body fat through densitometry (underwater body fat analysis or the “Bod Pod”) should be use to quantify body fat.

Part II.

“There is a new direction being touted out of Europe and embraced here,

called the waist/'hip ratio -- as opposed to BMI! Is it valid? I need some personal opinions, as well as medical basis for using this ‘waist/hip ratio’."

Waist Hip Ratio (WHR) is a method for assessing abdominal fat. This is important because increased total abdominal fat places individuals at higher risk for chronic illness regardless of their weight or BMI.1 However, WHR is not new. There is research using WHR as a tool for health risk assessment at least as long ago as 1990.6 Measuring Waist circumference (WC) alone is a simpler way of assessing for abdominal fat and has been shown by more recent research to be superior to WHR in determining health risks. 1

Waist Circumference Guidelines:

Men
*Any measurement above 40 for men or 35 for women indicates high abdominal fat and high risk for chronic diseases.

There has been some conflicting data regarding the relative merits of WHR vs. WC, but the current scientific consensus favors the use of WC. WHR is particularly inaccurate in women.7 The NIH and the USDA recommend the combined use of BMI and Waist circumference.3,8 This information is then made useful in health assessment by then looking at individual risk factors such as personal and family history, race, gender, ethnicity, diet and other personal characteristics.3 The combined information of all three of these tools (BMI, WC and health history) is more helpful than information from any one alone.

For example, a BMI of 28 identifies a high likelihood of risk for many chronic diseases. Waist circ of > 35 in an adult female tells us she is particularly at risk for cardiovascular diseases, diabetes and early death. A family history of diabetes allows us to pinpoint this person’s specific risk as Adult onset diabetes.

A Few Personal Opinions:

Many people have the impression that European-style health care is more progressive. For example, there is better equality of access and stronger emphasis on prevention. There are many differences between the systems in all of the European countries, however, so I try to avoid lumping them all into one category. All of them differ so drastically from the US system that making comparisons is problematic. In the U.S., for example, the average length of a Doctor’s office visit is now less than 20 minutes and getting shorter! There are many reasons for this, most notably increasing numbers of people suffering from chronic illness and decreasing insurance reimbursement. This necessitates the use of standardized screening tools by US providers that are accurate and quick.

I definitely do not agree with the recommendations of all government agencies. In this case, however, I believe the NHLBI is right on. The use of BMI and WC is supported by a vast amount of research. Combining these tools with a thorough health history is critical to their usefulness in health assessment. Their use to the average lay person is questionable. BMI in particular is more useful as a predictor of population health than of individual health. Anyone concerned about their weight should see their primary care provider for a complete history and physical to determine their risks.

About the Author:

I have been a Registered Nurse for 13 years, primarily working in cardiovascular nursing. I obtained my RN from the Geisinger Medical Center School of Nursing in Danville, PA in 1992 and have I been certified in medical surgical nursing by the American Nurses Credentialing Center since 1995. I have a Bachelor of Science in Nutrition from Bastyr University in Kenmore, WA and am currently a full time graduate student at the University of Washington in the Family Nurse Practitioner program. I serve as the Nurse Educator for Youth Take Heart, a cooperative heart health education program between MESA, UW Bioengineering, and the Hope Heart Institute.

Sources

1. Kuczmarski, RJ and Flegal, KM. Criteria for definition of overweight in transition: background and recommendations for the United States. Am J Clin Nutr 2000;72:1074–81).

2. CDC. BMI - Body Mass Index: BMI for Adults: Body Mass Index Formula for Adults. Online access Nov 8, 2005. Found at .

3. National Heart, Lung, and Blood Institute (NHLBI). 1998. Clinical guidelines on the identification, evaluation, and treatment of overweight and obesity in adults. NIH publication # 98-4083. Washington DC: National Institutes of Health, US Department of Health and Human Services.

4. CDC. BMI - Body Mass Index: BMI for Children and Teens. Online access Nov 8, 2005. Found at: .

5. Lee RD, Nieman DC. Nutritional Assessment, 3rd ed. McGraw-Hill: NY, 2003.

6. Kaye SA, Folsom AR, Prineas RJ, Potter JD, Gapstur SM. The association of body fat distribution with lifestyle and reproductive factors in a population study of postmenopausal women. Int J Obes. 1990 Jul;14(7):583-91.

7. Rankinen T, Kim SY, Perusse L, Desprs HP, Gouchard C. 1999. The prediction of abdominal visceral fat level from body composition and anthropometry: ROC analysis. Int J Obesity and Related Metabolic Research 23:801-809.

8. US Department of Agriculture and US Department of Health and Human Services. Dietary guidelines for Americans 2005. Washington, DC. Online access Nov 8, 2005. Found at: .

*This is an original document. Please do not alter or recreate any part without prior consent from the author: anstadtm@u.washington.edu

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