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The Navy Formula Body Fat Calculator

Bodybuilder Tom Venuto

Skinfold testing is our top pick for measuring and tracking your body fat percentage while on the Burn The Fat program. Few methods are as practical and accurate for private, in-home testing, over time, provided you have an experienced skinfold tester or you've mastered the skinfold "pinching" technique yourself. However, the skinfold method does have its drawbacks and for people who have a difficult time measuring skinfolds, there are alternatives...

One alternative is the circumference method. There are numerous circumference formulas available for estimating body fat and they are all based on the fact that while a tape measure cannot directly measure body fat, there is a correlation between body circumferences, the relationship between body circumferences, and your body fat percentage.

Like many other organizations that depend on the health and wellness of their personnel, the United States military realized that body weight is a poor measure of one's physical condition, because it does not distinguish between body fat mass and lean body mass. Twice each year, Navy personnel must pass a height and weight screening. But today, instead of stopping there, those whose body weight fails to meet standards, then have their body fat estimated. Although physical performance is also evaluated along with body fat, failure to reach body fat standards can result in discharge of valuable and highly trained personnel from the service, so the Navy needed a method for body fat prediction that was reasonably accurate, yet simple and inexpensive enough to test large groups of subjects.

As a result, body fat estimations were developed by the Navy at the Naval Health Research center in 1984, based on comparison with underwater weighing. Data has been collected from the use of this formula for many years and the methods have been studied and published in peer reviewed journals. Although you cannot expect great precision using this method (for example, don't expect to be able to measure the difference between 15.1% and 15.4%), research indicates that (1) the circumference method is a valid estimator of percent body fat, (2) the circumference method compares favorably to skinfolds and other circumference equations, and (3) the circumference method is valid across various races

We have selected the "Navy" circumference-based equation because both in research (see references) and in practice, it seems to provide a fairly good estimate of body fat percentage as compared with other circumference methods. We also like this formula because the circumference equations that use arm and leg measurements will overestimate muscular individuals and increases in extremity muscle girth will be translated as increase in fat mass (muscular individuals such as bodybuilders should use skinfolds or other methods).

Research has suggested that hip circumference is a good predictor of total body fat in women. However, after 17 years of use and data collection, it was noted that body fat prediction accuracy using the Navy formula was slightly better for men than for women. One drawback that you should be aware of is that hip measurement does not account for bone girth. Using circumference of hips will overestimate body fat in women with wide bone structure in the hips. However, once a baseline is established, the hip circumference is a good way to measure changes in body fatness with repeated measurements over time (If hip measurement is going down, then body fat is going down).

Another useful feature of this circumference equation is that the standard error is low as compared to skinfold measurements. Skinfold testing is not inherently inaccurate. The reason for so much potential inacuracy when using skinfolds is due to operator error. Although circumference methods are generally considered less accurate than skinfolds and other body fat testing methods, using a tape measure doesn't require much skill, so there is a smaller chance of operator error.

Remember that all body fat testing methods only provide an estimate and that accuracy is much less important than consistency and repeatability. If you measure your circumferences carefully, in the exact same spot every time, with the same tape measure and the same amount of tension on the tape (taut by not tight), than you are likely to get an acceptable body fat estimate - and more importantly, a consistent estimate that you can use to chart your progress.

Instructions:

To determine your bodyfat using this calculator, follow these simple steps:

1). Select the appropriate Gender
2.) Select either Inches or Centimeters and
3.) Enter your measurements into the appropriate boxes. (Note: Men only need to enter the first three site measurements and women need to enter all four site measurements.)

The Three Locations For Men:
The Four Locations For Women:
1. Abdomen: Horizontal at the level of the navel. This is not the minimal width. 1. Abdomen: Horizontal, at the level of minimal abdominal width.
2. Neck: Inferior to the larynx with the tape sloping slightly downward to the front. 2. Hip: Largest horizontal circumference around the hips.
3. Height: Is measured without shoes. 3. Neck: Inferior to the larynx with the tape sloping slightly downward to the front.
The formula for men: %Fat=495/(1.0324-.19077(log(abdomen-neck))+.15456(log(height)))-450
4. Height: Is measured without shoes.

The formula for women: %Fat=495/(1.29579-.35004(log(abdomen+hip-neck))+.22100(log(height)))-450
   

*All measurements taken to the nearest 0.5cm (ľ inch).

References:

1. J. Hodgdon. and M. Beckett: Prediction of percent body fat for U.S. navy men and women from body circumferences and height. Reports No. 84-29 and 84-11. Naval Health Research Center, San Diego, Cal. 1984

2. J. Hodgdon. and M. Beckett: Development of the DoD body composition estimation equations. Report No. 99-2B. Naval Health Research Center, San Diego, Cal. 1999

3. Friedl, et al, Evaluation of anthropometric equations to asess body composition changes in young women, American Journal Of Clinical Nutrition, 73: 268-275, 2001

4. Kujawa, K., & Hodgdon, J. Comparison of circumference- and skin-fold based body fat estimation equations. Naval Health Research Center Technical Report No. 98-34

5. Kujawa, K.I., Reading, J.E., Glover, W.L., & Hodgdon, J.A. Reliability of a four-compartment body fat estimation technique. Medicine and Science in Sports and Exercise, 31(5):S203, 1999.

6. Kujawa, K.I., Reading, J.E., & Hodgdon, J.A. Comparison of tape measures for body fat estimation. Medicine and Science in Sports and Exercise, 32(5):S87, 2000.

7. Kujawa, K.I., validity of navy circumference body fat equation in women of african-american, asian, hispanic, and filipina descent, Medicine & Science in Sports 7 Exercise, 34(5), S238, 2002

8. Kujawa, K.I., Comparison of cirumference-based and skinfold based body fat estimation equations, Medicine & Science in Sports & Exercise, 30(5), S277, 1998

9. Weltman, A., Accurate assessment of body composition in obese females, American Journal of clinical nutrition, 48(5): 1179-1183, 1988

10. Tran, Weltman, Predicting body composition of men from girth measurements, Human Biol, 60:167, 1988

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About Bodybuilding & Fat Loss Coach, Tom Venuto

Tom Venuto is a lifetime natural (steroid-free) bodybuilder, independent nutrition researcher, freelance writer and author of Burn The Fat, Feed The Muscle: Fat Burning Secrets of the World's Best Bodybuilders and Fitness Models (e-book) Tomís articles are featured on hundreds of websites worldwide and he has been featured in IRONMAN, Australian IRONMAN, Natural Bodybuilding, Muscular Development, Menís Fitness, Menís Exercise as well as on dozens of radio shows including Martha Stewart healthy living (Sirius), ESPN-1250 and WCBS. To get more information about Tom's e-book about natural fat loss and fat burning foods, visit the home page at: www.BurnTheFat.com




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