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NAVAL HEALTH RESEARCH CENTER
NAVAL HEALTH RESEARCH CENTER
DEVELOPMENT OF THE DoD BODY
COMPOSITION ESTIMATION EQUATIONS
J.A. Hodgdon
K. Friedl
Technical Document No. 99-2B
Approved for public release; distribution unlimited.
NAVAL HEALTH RESEARCH CENTER
P.O. BOX 85122
SAN DIEGO, CA 92186-5122
BUREAU OF MEDICINE AND SURGERY (MED-02)
2300 E STREET, NW
WASHINGTON, DC 20372-5300 DEVELOPMENT OF THE DoD BODY COMPOSITION ESTIMATION EQUATIONS
James A. Hodgdon, Ph.D.
Naval Health Research Center
San Diego, CA 92152
Karl Friedl, LTC, MS, USA
U.S. Army Medical Research & Materiel Command
Fort Detrick, MD 21702-5012
Technical Document No. 99-2B. This work was supported by the Department of Defense
(Personnel & Readiness) under work unit 6430. The opinions expressed in this report are those
of the authors and do not reflect official policy or position of the Department of the Navy, the
Department of the Army, the Department of Defense, or the United States Government. Human
subjects participated in this study after giving their free and informed consent. This research has
been conducted in compliance with all applicable Federal Regulations governing the Protection
of Human Subjects in Research. 2
Summary
This report summarizes the research findings that led to the policy decisions for
development of the body fat content screening procedures and equations that are currently under
consideration for inclusion in the Department of Defense (DoD) Instruction (DoDI) 1308.3,
Physical Fitness and Body Fat Programs.
At a DoD meeting on 21 May 1998, results of a review by the Committee on Body
Composition, Nutrition and Health, Military Nutrition Committee, Institute of Medicine were
presented. It was recommended that a tiered body fat content standard be adopted. A weight-
for-height screen would be adopted based on the recommendations of the Healthy People 2000
Committee: Healthy weights are represented by body mass index (BMI) values between 19 and
25, irrespective of gender. Service members exceeding the weight-for-height standards would
have their body fat content determined. Men with body fat content values less than 20% body
weight and women with values less than 30% body weight would be considered within
standards. Men with values greater than 20% fat, but less than or equal to 26% fat, would be in a
cautionary zone and acceptability of their body fat content would depend on performance on
the Services physical fitness test. For women, the cautionary zone values would be 30 to 36%
fat.
Results of work performed at the Naval Health Research Center (NAVHLTHRSCHCEN)
also were presented at the meeting. The use of a four-compartment model to determine body fat
content was shown to reduce the error variance associated with body fat content measurement by
13 to 20%. Additionally, the use of a four-compartment model eliminates a systematic
difference in body fat content estimation associated with ethnicity, which is inherent in the two-
compartment model.
A variety of equations predicting four-compartment body fat content from body
circumferences and height was presented. Prediction was shown to improve slightly by utilizing
a non-linear equation form involving logarithms. It also was found that prediction of four-
compartment body fat content from circumferences, as currently used by most of the Services,
and in the logarithmic transform equations currently used, did not differ significantly (p < 0.05)
in predictive accuracy from a variety of other model forms. It was recommended that work
continue on equation development and, further, among the equations presented, the current 3
circumference measures would be retained. It also was recommended that a research group from
outside DoD be contracted to conduct a parallel investigation to determine the best predictive
equations from circumference values.
On 9 October 1998, a second meeting was held to review progress. At this meeting,
researchers from Wright State University, Yellow Springs, OH, presented findings from the
parallel equation development. Their final model was judged too complex to be used. In
addition, the equations developed at NAVHLTHRSCHCEN were reviewed. Concern was raised
about the form of the four-compartment analysis used at NAVHLTHRSCHCEN, specifically
about the use of whole-body bioelectrical impedance analysis (BIA) to predict total body water
(TBW). The group decided to recommend retention of the equations currently in use by the
Navy and the Air Force. The rationale was that development of these equations has been
documented in technical reports. Thus, a review of their development and validity was possible.
In their original development, body density was predicted, and then converted to percent
fat. These equations were reformulated to allow direct prediction of percent body fat.
Additionally, predicted percent fat values were analyzed for the influence of moderating
variables. None were identified. The equations recommended for use by DoD were:
Men:
% body fat = 86.010 x log
10
(abdomen II - neck) - 70.041 x log
10
(height) + 36.76
(n = 594, R = 0.903,
SEE
= 3.52 % fat)
Women:
% body fat = 163.205 x log
10
(abdomen I + hip - neck) - 97.684 x log
10
(height) - 78.387
(n = 202, R = 0.856,
SEE
= 3.61 % fat) 4
Purpose
This report summarizes the research findings that led to development of the body fat content
equations currently under consideration for inclusion in the next Department of Defense (DoD)
Instruction (DoDI) 1308.3, Physical Fitness and Body Fat Programs.
Background
The Under Secretary of Defense (Personnel & Readiness), and Assistant Secretary of
Defense (Force Management Policy) sponsored a meeting at the Pentagon on 21 May 1998 to
review on-going research related to development of body fat content standards and prediction
equations.
A proposal for new body fat content standards derived, in part, from the findings of a review
conducted by the Committee on Body Composition, Nutrition and Health, Military Nutrition
Committee, Institute of Medicine, under the Defense Womens Health Research Program (1998).
LTC Karl Friedl of the U.S. Army Medical Research and Materiel Command presented these
findings. The principal features of the proposal were that: (1) a tiered approach to body fat
content standards be taken; (2) allowed levels of body fat content be tied to performance on the
Services physical fitness tests, and (3) the weight-for-height screening values be based on the
recommendations of the Healthy People 2000 (i.e., that healthy weights correspond to body mass
index [BMI] values between 19 and 25 kg
m
-2
, irrespective of gender or age) (Abernathy and
Black, 1996). The tiered body fat content standards consisted of three levels: first, a lower
boundary of 20% fat for men and 30% fat for women, at or below which body fat content is
judged satisfactory irrespective of performance on the physical fitness test. Second, a cautionary
zone of 20% < fat < 26% for men, and 30% < fat < 36% for women within which body fat
content is judged satisfactory only if the person performs well on the Service physical fitness
test. Determination of what constitutes performing well was to be left to the Services. Third, an
upper boundary of 26% fat for men and 36% fat for women above which body fat content is
judged to be unsatisfactory, irrespective of performance on fitness tests. This proposal differs
from current Service practices in that there is no adjustment of the standards for age and that
there is a tiered structure to the standards. Those in attendance at the meeting tentatively
accepted the proposal or said they would take it under advisement. 5
Researchers at the Naval Health Research Center (NAVHLTHRSCHCEN) in San Diego
were undertaking most of the on-going work in development of body fat content prediction for
the Services. This work focused on use of percent body fat, derived from a four-compartment
analysis of body fat content, as the criterion measure for equation development. Equations
currently in use by the Services used a two-compartment analysis of body fat content as the
criterion.
Dr. James Hodgdon presented the findings of the NAVHLTHRSCHCEN researchers. The
first presentation dealt with an explanation of four-compartment body fat content measurement.
The principal points were: first, that the assumption of equal fat-free mass density across
individuals, which is part of the commonly employed two-compartment model, is invalid. The
principal sources of deviation from this assumption, water and bone, can be measured and are
used with determination of the fat and non-fat components of the non-bone, non-water body to
make up a four-compartment analysis of body fat content. In the NAVHLTHRSCHCEN
analysis, bone mineral content of the body was measured by dual-energy x-ray absorptiometry
(DXA), and total body water (TBW) was estimated from bioelectrical impedance analysis (BIA).
Second, the deviations from the assumption of equal fat-free mass density differ systematically
across ethnic groups (e.g., African-Americans tends to have greater bone densities than
Caucasian-Americans). Predictions based on equations developed using a two-compartment
analysis will have systematic over or under estimation of body fat content associated with