1981 of the physical fitness of the military services (Study of the Military Services Physical Fitness, DoD, 1981). As a result of this study, the Department of Defense (DoD) issued Directive 1308.1 (1981) mandating that all services establish a system of body fat assessment to evaluate overweight. Weight-for-height tables such as the actuarial tables published by the Metropolitan Life Insurance Company, which established upper limits of weight for height that minimized risk of morbidity and mortality, were to be used as the initial screen. Assessment of body fat was to be performed on those who exceeded the maximum weight for their height. Fitness assessments were to be performed on all soldiers as well (see Chapter 3). Each service was given responsibility for establishing its own method of body fat assessment. The method generally chosen was that of skinfold thickness measurement and use of the Durnin-Womersley equation (1974) to predict percent body fat. The Marine Corps was the first service to validate and employ equations based on circumferential measurements for body fat assessment (Wright et al., 1980). In 1987, an amendment to the DoD Directive specified that a circumference-based body fat estimation procedure was to be used, standardized against the criterion method of hydrostatic (underwater) weighing. Subsequently, each of the other services derived its own gender-specific equations (Table 2-1), selecting by factor analysis the circumferential measurements and other factors that best predicted body fat as determined by underwater weighing of its own subject population (Hodgdon, 1992). Unlike those of the Army, Navy, and Marine Corps, the initial Air Force equation included an estimate of fat-free mass (FFM); however, this method was subsequently abandoned, and slight modifications of the Navy equations are now in use by the Air Force. The current standards are described in Table 2-2 and will be discussed in greater detail later.
According to DoD Directive 1308.1 (1981), which mandated body fat assessment, the maintenance of a desirable body composition was "an integral part of physical fitness, general health, and military appearance" (p. 1). The study panel that was given responsibility to set upper body fat limits for the DoD recommended upper limits of 20 percent body fat for men and 29 to 30 percent for women, based on information in the textbook of McArdle et al. (1981) showing that the average body fat of physically fit young men was 20 percent and that of fit young women was approximately 30 percent, corresponding to an average maximal aerobic capacity of 50 and 39 ml/kg/min for men and women, respectively (these body fat figures contained a margin of 5% to allow for deviation from the mean and measurement error). However, the DoD decreased the maximum allowable body fat for women from the recommended 29 to 30 percent to a figure of 26 percent, in the belief that it was desirable to recruit women whose body fat was closer to that of the average man, as such women, possessing a higher than average proportion of FFM, might also be more similar to men in strength and endurance. There has been considerable discussion regarding whether these original standards were based more on considerations or beliefs about fitness, health, or possibly appearance. According to Friedl (1997), the standards were intended to enhance readiness. However, except for the exclusion of extremely obese individuals, the standards could not select for fitness or performance capability; they were intended to promote fitness and prevent obesity.
A 1995 update to DoD Directive 1308.1 established new upper limits for body fat of 26 percent for men and 36 percent for women, however each service was permitted to set upper limits of less than 26 and 36 percent. Thus, for example, the Army maintains progressively increasing upper limits of body fat for increasing age (the upper body fat limit for women ranges