for BMI less than 19.0 were 4.8 ± 0.9 percent (SEM) for Army women, 3.6 ± 0.4 percent for Navy women, 6.8 ± 0.7 percent for Marine Corps women, 4.7 ± 0.4 percent for Air Force women, and 4.7 ± 0.4 percent for all active-duty women (prevalence rates for BMI less than 19.8, stratified by service, age, ethnicity, and rank, are reported in Table 6-4). The highest prevalence of low BMI is observed among Marine Corps women, women less than 20 years of age, Hispanic women, and officers. The recently completed Army Food and Nutrition Survey (Warber et al., in preparation) also did not estimate the prevalence of underweight (low BMI); however, when asked whether they were trying to gain weight, 2.8 percent of female respondents reported that they were trying to gain weight (4.6% of women 29 years and younger, and 0.7% of women 30–39 years of age). No data were available on the prevalence of low body fat among active-duty women, as body fat assessments would be performed only on individuals who exceed the maximum weight for their height. According to NHANES III data, the percent of civilian women with BMI less than 18.5 is 5.6 percent of women 20 to 29 years of age, 3.8 percent of women 30 to 39 years of age, 3.0 percent of women 40 to 49 years of age, and 2.4 to 2.5 percent of women 50 to 79 years of age; the prevalence of underweight is higher among Caucasian women than among African American and Mexican American women in the sample population (Personal communication, A. Looker, National Center for Health Statistics, Hyattsville, Md., 1997). As suggested by data from the two military surveys and NHANES III, the prevalence of low BMI is more significant among younger women. Nevertheless, military dietitians and other personnel contacted were unaware of any formal program or intervention to rehabilitate underweight or underfat personnel. A study of women in BCT found that those whose body fat was below 25 percent at enlistment tended to gain weight, body fat, and fat-free mass throughout the 8-wk program (in contrast, women who entered BCT with greater than 25% body fat tended to lose body fat, and those who entered at greater than 35% body fat tended to lose both fat and weight). No follow-up data were available on these women.

Data on the prevalence of overweight among military personnel are difficult to obtain. Central medical and personnel databases do not appear to contain information that would permit a determination of the incidence of personnel exceeding the body fat standards. Data from two large self-report surveys that use self-reported height and weight to calculate BMI suggest that the prevalence of overweight among active-duty women is comparable to or less than that of a similar population of civilian women; however, these surveys use the definition of overweight established by the Healthy People 2000 report, which is significantly higher than the age- and service-specific cut-offs used by the military. Thus, it is not possible to estimate from these data the percent of women who are out of compliance with the standard to which they are required to adhere, but it is clear that this figure is higher than the percent defined as overweight by Health People 2000 standards. Data from several surveys demonstrate that the percentage of active-duty women who are dieting and/or dissatisfied with their weight is significantly higher than the percent of women who are actually overweight, suggesting that many women who are not overweight are trying to lose weight. As will be discussed below and in Chapter 5, this has serious implications for health, fitness, and performance.