weight control regulations, fitness evaluations (physical fitness tests or PFTs), body fat standards for accession and retention, and an appearance standard. The directive, written by a group that included physiologists, mandated a weight control program that would use measurement of body fat as the final discriminator of fitness. In response, each of the services devised its own weight control regulations. The first tier could be a weight screen, but this would be followed, if necessary, by a circumferentially based body fat determination (based on equations) using the standard of hydrodensitometry, which was the best standard available at the time. The Marine Corps already had devised its own anthropometric equations, whose primary aim, according to Friedl, was appearance, since appearance was viewed as an indicator of fitness and performance.
Long-term health consequences were apparently only a secondary consideration to the developers of the original DoD standards. The original DoD recommendation limited body fat to 20 percent of body weight for men and 30 percent for women (15% and 25%, respectively, plus a 5% margin of error) based on physiological measures of fit young men and women, but some individuals providing input to the standards ordered a decrease in the 30 percent body fat for women to 26 percent because they saw no reason for women to carry that much more fat than men. A 1995 update of the original directive (DoDD 1308.1, "Physical Fitness and Body Fat Programs") now states that the maximum allowable limit for men is 26 percent and for women 36 percent, although each service maintains its own standards.
The current Army regulation (AR 600-9, 1986) contains allowances for age, with four age categories. In comparison, the Air Force regulation (AFPD 40-5, 1994) contains one age break at 30, while the Navy and Marine Corps regulations (OPNAVINST 6110.1D, 1990) are age neutral. The higher body fat allowance for Army personnel over age 40 (26 and 36%, for men and women, respectively) is at least health based, according to Friedl, since it corresponds to the BMI that is the surgeon general's threshold for increased cardiovascular risk. All services use gender-adjusted body fat standards.
The Army weight control program uses a weight-for-height screen as its first tier, followed by circumferential measures for those who exceed their weight limit. Data were shown from a 1988 study of male soldiers (O'Connor et al., 1990), illustrating that approximately half of those found to be overweight were within the allowable fat limits, which kept them out of the weight control program but which would be recorded in their records nonetheless.
The validity of the circumferential equations used by the military was discussed by Friedl (1996). Equations based on circumferential measurements replaced those based on the more commonly used skinfold measures because of the greater reliability of circumferential measures in field conditions. The men's equations differ slightly from one service to another, but all of them focus on a measure of abdominal circumference (since this is the primary site of male fat deposition), correcting for body size by measuring the circumference of the neck. Although these equations have been validated against underwater weighing (based on a tow-compartment model of body composition), the latter method, itself, may not be valid for several reasons. Many military subjects cannot swim, resulting in a skewed sample or incorrect determinations. Moreover, one of the assumptions made in interpreting the data is that there are no individual differences in bone mineral density (BMD), when in fact there are significant ethnic differences in BMD. Efforts are being made to identify a better criterion method, such as the use of dualenergy x-ray absorptiometry (DXA) (based on a three-compartment model) and a four-compartment model that incorporates DXA. Although the male equations compare well