History of the U.S. Navy Body Composition Program

Transcription

1 MILITARY MEDICINE, 180, 1:91, 2015 History of the U.S. Navy Body Composition Program CDR David D. Peterson, MSC USN ABSTRACT The Navy currently employs maximum weight-for-height tables and body fat prediction equations based on circumference measurements to assess body composition. However, many Sailors believe the current method fails to accurately predict body fat percentage. As a result, the Naval Health Research Center (NHRC) conducted numerous studies in an attempt to improve the accuracy and reliability of the Navy s Body Composition Analysis program. In 2012, NHRC conducted a study that researched the feasibility of using a single abdominal circumference (AC) measurement in lieu of circumference measurements. The Air Force and National Institutes of Health (NIH) employ a single AC measurement taken at the superior border of the iliac crest to assess body composition and all-cause mortality risk. Although the Air Force and NIH use the iliac crest, NHRC is proposing the Navy use the umbilicus as the AC site since it is less invasive and easier to identify. If implemented, the Navy would use cutoff values of 40 in. and 36 in. for males and females, respectively. The purpose of this article is to provide a brief history of the Navy s Body Composition Analysis program as well as propose the transition from circumference measurements to a single AC measurement. United States Naval Academy, 121 Blake Road, Annapolis, MD doi: /MILMED-D INTRODUCTION Numerous epidemiological and physiological studies have shown that increased body fat among U.S. military personnel is linked to increased injury and increased health risks as well as decreased physical performance and combat readiness. 1 4 Additional research indicated a strong correlation between excess abdominal adipose tissue and certain metabolic diseases (e.g., insulin resistance, impaired glucose tolerance, type 2 diabetes, dyslipidemia, and cancer). 4,5 Specifically, visceral fat, the deep fat surrounding the internal organs, is known to release free fatty acids and inflammatory proteins into the portal vein and therefore considered to be a major indicator of metabolic risk and dysfunction. 4 Other research has reported that waist circumference is inversely related to life expectancy. 5 To combat this, the Department of Defense (DoD) has required that each branch of service develop and implement a body composition program aimed at promoting regular exercise and good dietary habits. 6 In 1981, the DoD released DODI , which mandated each service to develop their own body composition program tailored to their respective mission. The following three considerations were provided: (1) body composition is an integral part of physical fitness, (2) body composition plays an important role in professional military appearance, and (3) body composition is a good indicator of the general health and wellbeing of military personnel. The directive allowed each individual service to develop the method used to assess body composition. However, the directive required that the method have a correlation coefficient of 0.75 or higher to the percent fat estimated from hydrostatic weighing (later increased to 0.85). Additionally, the directive required that maximum allowed percent body fat standards for all four services be set at 20% for males and 26% for females. 7 In 1998, the Under Secretary of Defense for Personnel and Readiness and Assistant Secretary of Defense for Force Management Policy ordered the review of the current DoDmandated body fat standards and prediction equations. As a result, the following three changes to the DoD were proposed: (1) a tiered approach to body fat percentage standards should be employed, (2) allowed levels of body fat content should be tied to service-specific physical fitness test, and (3) revise weight-for-height screening values to reflect the weight goals established by Healthy People 2000 (i.e., weights should correspond to body mass index values between 19 and 25 kg/m 2, irrespective of gender). 8 The tiered approach to body fat standards were tied to the physical fitness test by the following: (1) a lowered boundary of 20% body fat for males and 30% for females is considered satisfactory regardless of performance on the physical fitness test, (2) a cautionary zone of >20% to <26% for males and >30% to <36% for females within which body fat is considered satisfactory only if the member performs well (determination criteria left up to the individual services) on the physical fitness test, and (3) an upper boundary of 26% for males and 36% for females above which body fat is considered unsatisfactory regardless of performance on the physical fitness test. 8 Additionally, the proposal afforded no adjustment in maximum allowed body fat standards based on age. These recommendations were compiled and eventually resulted in the development and release of the DoD in May of The purpose of this article is to provide a brief description of the body composition analysis (BCA) used by the other services, discuss the purpose and history of the Navy s body composition program, explain why the Navy currently uses circumference measurements to assess body composition, MILITARY MEDICINE, Vol. 180, January

2 and provide recommendations for how the Navy could improve its body composition program. BCA PROGRAMS USED BY THE OTHER SERVICES Currently, all of the services, except for the Air Force, use circumference measurements and body fat prediction equations to assess the body composition of their members Each set of equations were developed specifically for each service and have similar validities and standard errors of measurement as compared to other published generalized anthropometric equations, and appear to be reasonable, useful estimators of body composition. 12 U.S. Marine Corps The Marine Corps was the first service to assess body composition through circumference measurements. The initial Marine Corps equations were developed by Wright et al 13,14 from the Institute of Human Performance from data collected by Wright and Wilmore 15 on 279 male and 181 female Marine Corps personnel. The current equations were developed by Naval Health Research Center (NHRC) and adopted in 1997 via Marine Corps Order B. The Marine Corps also uses the DoD weight-for-height tables. If a Marine exceeds maximum weight-for-height, but does not appear to fat, he/she may have a body fat estimation done. If the individual s body fat is less than the Marine Corps standard of 18% for males and 26% for females, a new maximum allowable weight is calculated and entered into the Marine s record. U.S. Army Initially, the Army released AR that used four site skinfolds (bicep, tricep, subscapular, and suprailiac) and the Durnin Womersley equations to assess body composition and comply with the DoD mandate. However, the Army had several concerns with implementing skinfolds and the Durnin Womersley equations. First, the training of nonclinical personnel on how to take skinfold measurements accurately placed a tremendous time and cost burden on designated Medical Department Activity representatives (usually a dietician or physical therapist). Second, the accuracy of the equations was affected by differences in age, gender, and degree of fatness. Third, these equations were developed for a homogenous and relatively sedentary population and did not accurately represent Army personnel. As a result, the Army Surgeon General s Office requested an alternative technique for body fat estimation be developed. In 1986, the Army released a revised AR that utilized circumference-based equations similar to those used by the Navy and Marine Corps. The current Army equations were developed by Vogel, Kirkpatrick, Hodgdon, and Harman (1988) at the U.S. Army Research Institute of Environmental Medicine on a 1,126 male and 266 female U.S. Army personnel. Maximum allowable percent body fat standards for the Army are provided in Table I. U.S. Air Force Initially, the Air Force used prediction equations and circumference measurements similar to the other services to assess body composition. The Air Force equation for males was developed by Fuchs et al 16 at the Air Force School of Aerospace Medicine. The equation for females was developed by Brennan (1974) as part of her Master s thesis at the Incarnate Word College in San Antonio, Texas (i.e., development of a binomial involving anthropometric measurements for predicting lean mass in young women). Unlike the equations of the other services, the Air Force equations predicted fatfree mass. In 2009, the Air Force submitted a request and was subsequently approved to use an abdominal circumference (AC) measurement (measured at the superior border of the iliac crest) to assess body composition. 17 The Air Force argued that the DoD weight-for-height table did not differentiate between fat and fat-free mass nor account for fat distribution pattern. 17 The Air Force also cited research suggesting that increased health risks (e.g., cardiovascular disease and various metabolic disorders) are more closely related to fat distribution than to total body fat. Additionally, reducing AC TABLE I. Maximal Allowable Body Fat Percentages (%BF)/Abdominal Circumference (AC) by Branch of Service Service Age %BF Men %BF Women AC Men AC Women Air Force >39 a >35.5 a 35 b 31.5 b Army Marine Corps Navy a High risk. b Moderate risk. 92 MILITARY MEDICINE, Vol. 180, January 2015

3 is more important than normalizing body weight since exercise can facilitate gains in muscle mass that can prevent or even cause weight gain. THE HISTORY AND EVOLUTION OF THE NAVY S BCA PROGRAM In 1982, the Navy drafted and released the OPNAVINST B in response to the DoD Directive The instruction used body fat prediction equations developed by Wright, Dotson, and Davis until Navy-specific equations could be developed. 18 The Wright, Dotson, and Davis equations were developed for and used by the U.S. Marine Corps and employed circumference measurements to estimate body fat percentage. Specifically, neck and abdomen (umbilicus) circumference measurements for males; and neck, abdomen (umbilicus), biceps, forearm, and thigh circumference measurements for females. 19 The initial maximum body fat percentage was set at 22% for males and 30% for females and did not change with age. However, the maximum body fat percentages were raised to 23% for males and 31% for females in the 45 to 49 age group and 24% for males and 32% for females in the 50 years and older age via the release of OPNAVNOTE 6110 in The release of OPNAVINST C in 1986 changed the equations used for body fat prediction from those developed by Wright, Dotson, and Davis to those developed by the NHRC. Similar to the Wright, Dotson, and Davis equations, the NHRC equations were based on circumference measurements. Specifically, abdominal (umbilicus) and neck circumferences for males, and neck, natural waist, and hip circumferences for females. Body fat percentage was estimated via charts that plot the member s height against the sum of their circumference values. Additionally, a two-tiered model was developed for scoring body composition. Males who exceeded 22% body fat and females who exceeded 30% were classified as overfat and males who exceeded 26% and females who exceeded 36% were classified as obese. Individuals classified as obese were sent for a medical examination and not allowed to participate in the Physical Readiness Test (PRT). Individuals who remained in an obese classification after 16 months were eligible for administrative separation. In 1993, the Navy implemented a single standard of 22% and 30% body fat for males and females, respectively, via the release of Naval Administrative (NAVADMIN) 071/93. As a result, the number of Physical Fitness Assessment (PFA) failures more than doubled from 1993 to In fact, the number of separations because of BCA failures increased from an average of 982 Sailors per year from 1990 to 1993 to an average of 2,240 per year from 1995 to Before 1994, all Sailors were required to have their body fat assessed by circumference measurement. However, NAVADMIN 148/94 now required the use of a weightfor-height table as an initial screening for body fat assessment. For each of the weight-for-height references, an estimated body fat percentage was assigned based on prediction equations developed by NHRC. Although the weight-for-height table was relatively easy to use, the body fat percentage values were not the same across heights and did not correlate well with the body fat percentage table employed by the DoD Instruction NAVADMIN 229/94 allowed Sailors who exceeded body fat standards to apply for a unique body structure waiver. The intent was to afford relief to Sailors whose body dimensions were such that they were reported as being outside of allowed body fat standards when in fact they were not. 18 To qualify for the unique body structure waiver, the member must meet the following three criteria: (1) score an Excellent or Outstanding on the PRT, (2) provide medical documentation of being in excellent health and possessing a unique body structure (as determined by an authorized medical department representative), and (3) have no previous attendance in a military-sponsored weight-loss program. 18 In 1995, the Navy released NAVADMIN 315/95, which replaced the weight-for-height table from NAVADMIN 148/94 with that contained in the DoD Instruction. As before, the new table still did not correlate perfectly with the new body fat standards as outlined in NAVADMIN 071/93 (i.e., 22% for males and 30% for females). In September 1998, the Navy adopted a new weightfor-height screening table via the release of OPNAVINST E. NHRC developed the new table using its equation for prediction of body fat content from weight and height. 18 Additionally, OPNAVINST E changed the maximum body fat percentage for females from 30% to 33%. However, the maximum body fat percentage for males remained the same (i.e., 22%). Beginning in November 2005, NAVADMIN 180/05 allowed Commanding Officers and Officers in Charge to increase allowed body fat standards to the DoD maximum of 26% for males and 36% for females as long as the following criteria was met: (1) Sailors must achieve an overall score of Excellent or Outstanding on the PRT, without scoring below Good on any event and (2) Sailors must present a professional military appearance. However, NAVADMIN 131/10 rescinded NAVADMIN 180/05 effective July 1, As a result, any Sailor who exceeds the Navy s body fat percentage standards would fail the PFA. WHY THE NAVY USES GENERAL HEALTH AS THE BASIS FOR BODY FAT STANDARDS As mentioned previously, the DODI mandated that each service develop a body composition program based on at least one of the following considerations: physical fitness, military appearance, and/or general health. NHRC conducted a series of studies to determine which consideration best aligned with the Navy s mission. In 1987, Hodgdon and Beckett 19 investigated the association between body composition, PRT modalities, and performance MILITARY MEDICINE, Vol. 180, January

4 of load-carrying tasks. The results showed only a modest correlation between body fat and PRT as well as body fat and load-carrying performance. This modest correlation suggests that basing percent fat standards on PRT or load-carrying performance would not be overly beneficial or relevant. In 1990, Hodgdon, Fitzgerald, and Vogel conducted a study comprised of 11 Army headquarters staff to rate the military appearance of 1,075 male and 251 female Army personnel in their Class A uniform. A 5-point scale was used for the ratings. Although the inter-rater reliability was quite high (0.86), the correlation between appearance and percent body fat was modest (0.53). The results suggest that military appearance by itself is not a reliable predictor of body composition. The National Institutes of Health (NIH) convened a consensus development conference in 1985 to discuss the health implications of obesity. The conference attendees determined that obesity leads to an impairment of health and increased risk of certain metabolic diseases. Additionally, the attendees defined obesity as a weight-for-height 20% above the midpoint weight referenced in the 1983 Metropolitan Life Insurance tables for the medium-frame individual. In 1991, NHRC conducted a study to determine whether the Metropolitan Life Insurance tables could be used to develop percent body fat standards. Using a specified Navy anthropometry data set, NHRC developed equations that calculated the regression between weight and height, and percent body fat. Using these regression equations, NHRC determined the percent fat value associated with the critical weights at each height for both males and females. Interestingly, the critical percent fat values were rather constant across heights, especially for females. Mean values for critical percent fat across height were 22.0 ± 1.20 for males and 33.5 ± 0.18 for females. 12 Navy percent body fat standards later were derived from these mean values. WHY THE NAVY USES CIRCUMFERENCE MEASUREMENTS Although the DODI only provided the services with three basic considerations for determining which technique to use for assessing body composition (i.e., physical fitness, military appearance, and general health), other factors must be considered in identifying a suitable technique for assessing body composition. For example, the measurements need to be easily obtained in the field and the skill required to take the measurements must be relatively easily acquired. 12 As a result, all four services opted to use circumference measurements, at least initially, as the basis for their body composition programs. Up until 1990, all four services used body fat prediction equations derived from a two-compartment analysis (i.e., fat mass and fat-free mass) of body density as determined by underwater weighing. In 1996, NHRC conducted a study in an attempt to develop a four-compartment criterion method for body fat prediction. The results revealed that AC for males and waist circumference for females were the best predictors of body fat content and that the two-compartment and four-compartment body fat prediction models were equivalent, irrespective of additional variables. 8 These findings suggests that the variables used in the current twocompartment model used by the Navy are just as accurate at predicting body fat content as any other variable combination. As a result, there is no compelling reason to transition to a four-compartment model that also measures bone mineral content and total body water. In 1998, NHRC conducted a study involving 22 novice PFA testers to determine the number of practice trials necessary to perform consistent and precise skinfold and circumference measurements. 20 Each tester conducted a series of three measurements per site on a different test subject until 120 triceps skinfold and 75 waist circumference measurements were completed. After completing 15 skinfold measurements the technical error of measurement (TEM), calculated for each novice tester at each site after completing eight sets of 15 skinfold trials and five sets of 15 circumference trials, was mm (18% error from the criterion value), compared with the TEM of mm (7.43% error) after completing 120 skinfold measurements. Conversely, the TEM for circumference measurements was cm (1.15% error) and cm (0.7% error) for 15 and 75 trials, respectively. 20 These results suggested that novice testers can become proficient in taking circumference measurements in as few as 15 practice trials, whereas it requires more than 120 practice trials to become proficient in performing skinfold measurements. In 1999, NHRC conducted a second study (i.e., Comparison of Circumference- and Skinfold-Based Body Fat Estimation Equations (Report No )) that compared the accuracy of Navy s equation to that of three popular skinfold- (i.e., Behnke and Wilmore [1974], Durnin and Womersley [1974], and Jackson and Pollack [1980]) and one bioimpedance-based (i.e., Lohman [1992]) equations Since all of the equations evaluated were developed using hydrostatic weighing as the criterion measure, hydrostatic weighing was used again as the criterion for accuracy. The results showed no difference in predictive ability between the Navy equation and any of the other equations for females. However, NHRC concluded that the Navy equation was the better predicator of body fat percentage for males. It was also determined that the circumference-based method is the preferred means of body composition assessment because of the fact that circumference measurements are more precise and easier to learn and administer than skinfold measurements, and that it has fewer technical factors (e.g., electrode placement, hydration status, timing of meals, ambient air, and skin temperatures) and a significant cost advantage over bioimpendance. WHY THE NAVY SHOULD USE AC In 2012, NHRC conduct another study (i.e., A Revised Equation for Prediction of Body Fat Content in Navy Women 94 MILITARY MEDICINE, Vol. 180, January 2015

5 TABLE II. Heath Risk Category Proposed BCA Standards Pass/Fail BCA Male (Inches) Female (Inches) Low Risk Pass Moderate Risk a Pass >35 <40 >30 <36 High Risk a Fail ³40 ³36 a Requires medical evaluation/consultation. [Delivery Order No. 0007]) to determine maximum allowable AC values that could be used in lieu of the current circumference-measurements in an attempt to more accurately assess body composition. This study was conducted, in part, based on the NIH findings that showed abdominal fat content is highly correlated to all-cause mortality risk and that abdominal girth is a good indicator of that risk. The NIH sets the criteria for high risk, measured at the superior border of the iliac crest, at 40 in. for males and 35 in. for females. It is recommended, however, that the Navy adopt an abdominal measurement taken at the umbilicus for the following reasons. First, the Navy uses an umbilicus measurement as part of its current BCA program and therefore would require no additional training/familiarization to implement. Second, the prediction accuracy of measurements taken at the umbilicus is comparable to those taken at the iliac crest Third, it is a less invasive and easier landmark to identify than the iliac crest. Mason and Katzmarzyk 21 reported that sites that use external landmarks (umbilicus and minimal waist) are easier to find in both males and females. Conversely, sites that use bony landmarks (e.g., iliac crest) require more training and experience to locate. Additionally, it is more difficult to stabilize the tape at bony sites as compared to those that use external landmarks. Table II provides the proposed umbilicus circumference value for both males and females. NHRC established these values using prediction equations developed by Mason and Katzmarzyk 21 that allows for the determination of a particular AC value based on known circumference values at other abdominal sites. NHRC calculated equivalent high-risk values for the umbilicus value based on the NIH high-risk values for the iliac crest (i.e., 40 in. for males and 35 in. for females). These values were calculated to be 40.2 in. for males (although NHRC recommends employing 40 in. as the standard) and 36 in. for females. Table III depicts the potential increase in the number of BCA failures for both males and females if the new BCA standards were adopted. IMPLEMENTATION CONSIDERATIONS It is recommended that every Sailor have an umbilicus circumference measurement taken regardless of whether they are in weight-for-height standards to better assess their health risk. Additionally, the following implementation criteria are recommended for scoring: (1) Sailors with an umbilicus value ³40 in. for males or ³36 in. for females would subsequently fail the BCA, regardless of whether they are within weight-for-height standards, and be required to report to medical for evaluation and (2) Sailors with an umbilicus value >35 in. (but <40 in.) for males and >30 in. (but <36 in.) for females would subsequently pass the BCA but be required to receive a medical evaluation. That said, Sailors meeting the second criteria (i.e., >35 <40 in. for males and >30 <36 in. for females) on subsequent cycles are not required to report to medical unless the umbilicus value has increased. Another possible recommendation would be to make the BCA portion of the PFA unannounced. In doing so, this would require Sailors to monitor their umbilicus value and maintain a healthy weight year round instead of just before the PRT. DISCUSSION Research has shown that circumference measurements are easier to teach than skinfolds and just as accurate and reliable as bioimpedance-based techniques. As a result, all of the services, excluding the Air Force, currently use circumference measurements to assess the body composition of their personnel. However, circumference measurements can undeservingly favor members who have a large neck. In fact, a large percentage of military personnel who are currently passing the BCA via circumference measurements would fail if tested using a single AC value (e.g., iliac crest or umbilicus). Research has also shown that AC values are strongly correlated to certain metabolic health risks and that reducing AC is more important than falling within a specific weight-for-height range. In terms of measuring site, the umbilicus is preferred over the iliac crest as it is easier to locate/measure and is already being used by the Navy. The implementation of the umbilicus measurement would improve the validity of the Navy s BCA program by providing a viable health screening for all Sailors as well as better identify those who are outside of allowed body fat standards and at greater risk of certain metabolic diseases. Additionally, the proposed changes would better align the Navy s BCA program with the DoD s intent for developing service-specific body composition programs as mandated by the DoD /3. TABLE III. Percent Failure Increase If Proposed BCA Standards Were Implemented PFA Cycle USN Males (%) USNR Males (%) USN Females (%) USNR Females (%) 1, , , MILITARY MEDICINE, Vol. 180, January

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