Formula Medical Group
Apple Valley, CA
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James Krider, MD


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Body circumference

CONCLUSION: The only two circumferences you really need are the waist and hip. Each is a separate and apparently independent predictor of potential health problems. While some investigators obtain ratios of the two measures, I feel that each should be looked at independently. IF you want to use the Navy Equations to predict body fat, THEN you also need include a neck circumference.

Body circumferences are a surprisingly simple and reliable measurement. In calculations of total body fat the circumference is preferred over skin folds since you have a much larger measurement that is less prone to error. The circumference also changes more during weight gain/loss so it is possible to detect smaller changes over time.

The major errors that can effect prediction equations are large muscles (body builders) and edema. Of all the sites, the most important two are at the waist (WC) and the hip. The WC has proven to be a pretty good predictor of visceral, or deep abdominal fat (VAT), and can account (predict) about 60 – 70% of the VAT.

It also turns out that the WC is probably the single best predictor of potential health problems such as diabetes, high blood pressure and heart disease – better than the BMI or waist-to-hip ratio. A general rule of thumb established by the World Health Organization (WHO) is to keep the WC below 40 inches for men and 35 inches for women.

WHO guidelines

Men

Women

Low risk

< 36.5 inches

<31 inches

Increased risk

36.6 – 39.75 inches

31.5 – 34.25 inches

Substantial risk

Equal to or over 40 inches

Equal to or over 35 inches

More detailed studies of the BMI and WC have shown that the increased risk of various health problems with an increasing BMI can be totally explained by the WC. So, if you do use the WC, then the BMI does not add any additional predictive properties.

This table shows the relative increase in risk of different diseases with each increase of BMI by one point or the WC by 1 cm (0.4 inches).

 

MEN (7,385)

WOMEN (7,539)

 

BMI by 1 point

WC by 1 cm

BMI by 1 point

WC by 1 cm

Hypertension

13%

4%

13%

5%

Hypercholesterolemia

7%

3%

8%

3%

High LDL

16%

2%

8%

4%

Low HDL

20%

6%

11%

4%

High triglycerides

20%

7%

13%

6%

Metabolic syndrome

20%

7%

15%

6%

Janssen Et. Al. Waist circumference and not body mass index explains obesity-related health risk. The American Journal Of Clinical Nutrition, 2004;79:379-84.

As example, if a man’s waist increased by about ½ an inch, his risk of developing hypertension will increased by 4% and the risk of developing the metabolic syndrome (which includes diabetes) increased by 7%. A woman has an increased risk of 5% and 6% respectfully.

But, big hips might be able to save you. Several studies now show that an increased size of the hips and thighs have an independent protective role for several diseases, especially diabetes. As a result of these studies it is suggested that the waist and hips be evaluated independently rather than by the waist to hip (WHR) ratio previously used. We do not know why this protective effect occurs – from more muscle mass, a different type of fat, or ???. But, I DO NOT recommend gaining weight to increase your hip size

If you do use the WHR, then in general, men over 0.9 and women over .85 have excess abdominal fat. The waist for the WHR is measured midway between the lower ribs and iliac crest (WC3), which may or may not be the narrowest.

EQUATIONS

The WC can give a reasonable estimate of VAT. For the following equations for VAT the waist is measured at WC4, which corresponds to the level most CT and MRI scans are done to measure VAT.

     
MEN VAT(cm 2) men = -453.7 + 6.37*WC R(2) = .56, SEE 66 cm(2)
WOMEN VAT(cm 2) women = -370.5 + 4.04*WC + 2.26*age R(2) = .68, SEE 42.1 cm(2)
Children 7-16 VAT(cm 2) = 1.1 x WC(cm)-52.9 R(2) = .648, SEE 13 cm(2)
YMCA Men fat pounds = (4.15 * (WC inches)) – (0.082*(weight in pounds)) – 98.42  
YMCA Women fat pounds = (4.15 * (WC inches)) – (0.082*(weight in pounds)) – 76.76  
NAVY Men %fat=495/(1.0324-.19077(log(abdomen-neck)) + .15456(log(height)))-450 R(2) = .89; SEE 3.12%
NAVY Women %fat = 495/(1.29579-.35004(log(abd+hip-neck))+.22100(log(height)))-450 R(2) = .89; SEE 3.16%

for VAT waist is measured at the W4 level.
YMCA - waist is measured at the navel.
% body fat = fat/weight
NAVY - Men are measured at the belly button and women at WC2 or narrowest abdomen. The neck is measured beneath the Adam’s apple, sloping slightly downward. All measurements are in centimeters.

One of the best equations that I have found is the Navy equation. The main limitations that I see are that it was developed using Navy personnel whose BMI did not exceed 30 (overweight), were younger, and physically active. I have not found any studies applying this formula in the sedentary obese population. The navy equation showed a high correlation of nearly 89% for both men and women compared to underwater weighing and DXA. The error in predicting %BF in men was 3.12% and 3.16% in women.

If you want just one site to measure and use that site for all the above equations, I would recommend following the sites used by the Navy equation. The amount of error introduced into the other equations is not enough to warrant following all the different measurements. KISS.

This article was last reviewed February 1, 2006 by Dr. James Krider.

BIA
BIA test preparation
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BMI
Body circumference
Body circ technique
Body compartments
Body comp methods
Body measurements
Skinfolds
Skinfold technique
Skinfold calipers

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