Assessing Fitness versus Fatness

One of the considerations most relevant to the issue of fitness in the military is how fitness should be assessed. As described in the recently revised Department of Defense (DOD) Physical Fitness and Body Fat Program Procedures (DOD, 2002), the four components of fitness assessment are: (1) aerobic capacity, (2) muscular strength, (3) muscle endurance, and (4) body composition, which is influenced by other measures of fitness. Fatness, as defined by DOD, means a body-fat content in excess of 26 percent of total weight for men and 36 percent of total weight for women.

Fitness and fatness are frequently confused due to the methods used to express data related to fitness. For example, the definitive measure of cardiorespiratory (i.e., aerobic) fitness is the determination of maximal oxygen consumption (VO_2max). VO_2max is usually measured while the subject is exercising on a treadmill, according to a defined protocol that gradually increases speed and incline, until voluntary exhaustion and maximal heart rate are achieved. Maximal heart rate is usually estimated as a heart rate of 220 minus the subject's age. The most appropriate expression of VO_2max is as ml O₂/min, or as ml O₂/kg fat-free mass/min. The effects of training on cardiovascular endurance may increase VO_2max by approximately 20 percent. Unfortunately, however, in many studies VO_2max is expressed as ml O₂/kg body weight. Because this expression includes fat, which does not increase oxygen consumption in response to exercise, VO_2max expressed as ml O₂/kg body weight may reflect differences in performance, but does not allow comparisons of cardiovascular fitness.

Fitness, Fatness, and Injury

Jones and colleagues (1992) studied the relationship of fitness and fatness (percent body fat) on injury rates of recruits during entry training at Fort Jackson, South Carolina, in 1984 and 1988. Fitness was defined on the basis of 1- or 2-mile run times and the number of sit-ups and push-ups completed during a 2-minute interval. All three fitness measures were highly correlated to fatness in both men and women. In men, percent body fat, determined from four skin-fold measures, was significantly and positively correlated with 1- and 2-mile run times and inversely correlated with the number of sit-ups and push-ups. Fitness was positively correlated with body mass index (BMI) as well, except no significant relationship was found for number of push-ups. Among women, the results of the three fitness tests were also positively correlated with percent body fat, although the strength of the relationships was weaker. BMI was positively, but weakly, correlated with 1-mile run and weakly, but inversely, correlated with push-ups. However, in a subsequent study of female Army initial entry trainees, Sharp and colleagues (1994) found that women who failed the percent body fat standard performed significantly better on physical performance measures of strength. For men, injury rates were directly correlated with percent body fat; for women, the highest rates of injury occurred in the leaner groups. Among both men and women, faster run times were associated with increased injury rates. In a multivariate analysis, the odds ratio for injuries to women was 2.5 times those for men. In analyses stratified by gender, both fatness and fitness independently accounted for significant proportions of the variance in injury rates.

Fitness, Fatness, and Mortality

Fitness may be an independent predictor of mortality. In a series of studies, Blair and coworkers (1989) have shown that fitness, defined as maximal treadmill time, was inversely associated with mortality, even after control for a variety of other variables linked to early mortality, such as serum cholesterol, blood pressure, and blood glucose. However, the highest mortality rates occurred in the least fit individuals with the lowest BMIs. In subsequent studies, Caucasian men who maintained or improved adequate levels of fitness had lower mortality rates than men who were persistently unfit (Blair et al., 1995). In more detailed studies of the relationship of obesity and fitness, low fitness appeared to increase mortality rates among men in all weight categories and carried a risk comparable to other cardiovascular risk factors (Wei et al., 1999). In another study (Lee et al., 1999), men who were lean and unfit had a higher mortality rate than men who were obese and fit. These results suggest that fatness and fitness may have independent effects on mortality.

Caution is needed, however, in applying the data related to fitness and fatness reviewed above. First, the most comprehensive studies derive from a single patient population (Caucasian men). Therefore, the generalizability of these observations to other populations may be limited. Second, in many of the earliest papers, VO_2max was measured during submaximal exercise, but it was expressed as ml O₂/kg body weight. Because obesity was defined on the basis of BMI, individuals with increased BMIs may have been spuriously classified as obese. This difficulty was only partially addressed by the analyses of the effect of fitness within BMI categories. A more recent study examined the relationship of BMI, cardiorespiratory fitness, and all-cause mortality in women (Farrell et al., 2002). After adjusting for age, smoking, and baseline health status, the authors found that compared with normal-weight women, overweight and obesity did not significantly increase all-cause mortality. However, women with moderate and high cardiorespiratory fitness had significantly lower mortality risk compared with those with low cardiorespiratory fitness. These highly promising results suggest that the military focus on the physical fitness of personnel is appropriate not only for performance, but also for overall health.

Accession Standards

Each of the services maintains gender-specific, weight-for-height and body-fat standards for accession (entry) into active military service in order to prevent the entry of overfat individuals. In the Army and Navy, accession standards are more liberal than retention standards, and the Army accession weight-for-height standards change with increasing age (see Table 2-1). Accession standards for all the services, based on BMI, are presented in Table 2-2. Body-fat standards for accession and retention are presented in Table 2-3. Currently, the Navy's body-fat accession standard is 1 percent higher than its retention standard. The Army accession standard is more liberal relative to the retention standard for men than it is for women. This is based on evidence that male recruits lose weight during initial entry training and early in their enlistment and maintain the weight loss, while women may lose weight during initial entry training, but tend to regain some of it (Friedl et al., 1989). Accession standards for the Air Force and Marine Corps are the same as their retention standards.

TABLE 2-1

U.S. Army Maximum Weight (lb)-for-Height Accession Standards by Age.

TABLE 2-2

Maximum Body Mass Index (BMI) (kg/m²) for Height for Accession.

TABLE 2-3

Maximum Body Fat (%) for Accession and Retention.

Because an accurate measurement of height and weight is considerably easier than an accurate measurement of percent body fat, the initial body composition screen for accession consists of a weight-for-height assessment using service-specific maximum allowable weight-for-height tables. Height and weight can be used to compute BMI, a widely accepted surrogate index of percent body fat (Gurrici et al., 1998; IOM, 1992a; NHLBI, 1998; Strain and Zumoff, 1992; Wang et al., 1996). It should be noted, however, that the military standards for maximum weight-for-height were established long before the science supporting the use of BMI was developed.

When only two measurements are used, height and weight have the highest level of association with the percentage of body fat. However, each service has conducted extensive anthropometric measurements of service personnel and used these data, together with data on body composition, to assess the best single additional measurement for estimating body fat (Friedl, 1992; Hodgdon, 1992). Until quite recently (DOD, 2002), none of the services had adopted the BMI per se as an alternative to maximum weight-for-height standards. However, the Air Force has considered BMI as part of the evaluation process before assigning an overweight individual to a weight-control program.

The maximum allowable weights-for-height have varied across services for individuals of the same height, age, and gender. The individual service standards were uniformly more stringent than the DOD recommendations. For example, as reviewed by the General Accounting Office (GAO, 1998), in 1998 the maximum allowable weight-for-height corresponded to a BMI of 25.1 for women in the Army, whereas for women in the Marine Corps, it corresponded to a BMI of 23.8. The disparity in maximum BMI between men and women was marked: while the maximum allowable weight-for-height for women in any service corresponded to a BMI of 25.1 (Army), for men it corresponded to a BMI of 28.2 (Air Force) (GAO, 1998).

However, in the recent revision of DOD Instruction 1308.3 (DOD, 2002), the weight-for-height tables have been revised to correspond to an upper-limit BMI of 27.5 and a lower limit BMI of 25, and it specifies that no service shall set more stringent screening weights than those corresponding to a BMI of 25. Thus, the Marine Corps had to raise its previous standard of 23.7 for women, while the Air Force had to decrease its previous standard of 28.2 for men.

Prospective recruits who exceed the accession weight limit for their height must undergo a body-fat assessment. The maximum allowable percentage of body fat for women on entry into the service ranges from 26 percent to 34 percent, depending on the service and for the Army, age. The maximum allowable percentage of body fat for men on entry into the service ranges from 18 percent to 26 percent depending on service and age (USAF, 2002; U.S. Army, 1987; U.S. Navy, 2002; USMC, 2002) (see Table 2-3). Each service uses circumference measurements to estimate body composition and, until recently, each employed its own set of measurement equations. However, as of November 2002, DOD has mandated a single circumference equation to be used across all the services for assessing percent body fat in men, and a different equation to be used in women.

In 1998, the Navy adopted a maximum standard of 23 percent body fat for men and 34 percent for women (Hodgdon, 1999). In setting these standards, the Navy consensus panel recognized that measures of height and weight “only approximate the precise magnitude of fatness,” and that lack of a strong relationship may lead to inaccurate classifications. However, height and weight were the only measurements for which a great deal of epidemiological data were available (Hodgdon, 1999). Ideally, more sophisticated body-fat measurements should augment the weight-for-height indices.

Setting accession standards has implications for recruiting. When the services set restrictions on recruitment eligibility based on weight-for-height and estimated percent body fat, they eliminate a portion of individuals who might otherwise qualify for service. In the Third National Health and Nutrition Examination Survey (NHANES III), 59 percent of the men and 51 percent of the women in the survey over age 20 years exceeded recent guidelines (NHLBI, 1998) that suggest that men and women are overweight when they exceed a BMI of 25 (Flegal et al., 1998; Kuczmarski et al., 1997).

Nolte and coworkers (2002) recently examined NHANES III data to determine the percentage of the U.S. population between the ages of 17 and 20 years that would meet the military weight-for-height standards that were in effect at the time the study was conducted. Their analysis indicated that 13 to 18 percent of men and 17 to 43 percent of women in this age range exceeded the military standards. The authors concluded that these data indicated a need for the military to reassess their standards. Perhaps a more appropriate conclusion (particularly for long-term health) would be to highlight the need for weight-gain prevention strategies targeted towards adolescents, particularly minority women. Data from the 1999–2000 NHANES indicate that BMI continues to increase, with the most recent data indicating that the prevalence of overweight and obesity in all men over the age of 20 years has now increased to 67.2 percent, while prevalence in women over the age of 20 years has risen to 61.9 percent (Flegal et al., 2002).

TABLE 2-4

Maximum Permissible Body Mass Index (BMI) (kg/m²) for Given Height for Retention.

Retention Standards

The retention standards are the maximum weights-for-height and percent body fat that military personnel are allowed to avoid referral to a weight-management program (DOD, 1995). The current BMI retention standards for men and women for each military service are presented in Table 2-4. The maximum allowable percentage of body fat for men ranges from 18 to 26 percent depending on service and age, while for women it ranges from 26 to 34 percent (See Table 2-3).

Each of the services screens active duty personnel either annually or semiannually for fitness and compliance with weight-for-height standards. Personnel may be screened several times a year in the course of medical examinations, physical fitness tests, or training school examinations. Thus, personnel receive regular feedback on how well they meet the standards of weight-for-height. The consequences of these practices are clear. In the NHANES III study, 34 percent of civilian men and 36 percent of civilian women over age 20 years exceeded a BMI of 27 (NCHS, 1998). In contrast, in a 1998 worldwide survey of active duty military personnel from all four services (n = 17,264), only 21 percent of active duty men and 9 percent of active duty women exceeded a BMI of 27. Additionally, 57 percent of active duty men and 25 percent of active duty women exceeded the newer overweight standard of 25, compared with 59 percent and 51 percent of civilian men and women, respectively (Bray et al., 1999; Flegal et al., 1998).

Because the data from Bray and coworkers (1999) are self-reported rather than actual measurements, some bias may exist. However, investigators who collected both self-reported data and actual measurements concluded that such biases were small. They found that correlation between self-reported data and actual measurements was high (R ≥ 0.82), and that self-reported data enabled investigators to classify weight category correctly 94 percent of the time (Jeffery, 1996; Strauss, 1999). Moreover, the data of Bray and coworkers (1999) were taken from surveys completed anonymously and collected by personnel who were outside the military chain of command of the respondents. Thus, these data most likely accurately portray the scope of the problem of overweight in the military services.

The Impact on the Health Care System

Another way to assess the impact of body-fat standards on the military is to estimate their cost to the health care system. In 1998, according to the Defense Medical Epidemiology Database (DMED)¹, active duty personnel made 9.1 million visits² to ambulatory care clinics. Just over 40,000 of those visits were for a primary diagnosis of “obesity” or “localized adiposity.”³ An additional 2,700 visits were for a primary diagnosis of “anorexia,” “bulimia,” or other “eating disorder.”⁴ That is, less than one-half of 1 percent of all ambulatory visits made by active duty personnel were recorded as being primarily for concerns about body weight, body composition, or dysfunctional weight-loss practices. A different approach was reported by Robbins and colleagues (2002), who examined anthropometrics, demographics, and health behaviors of 4,974 active duty Air Force men and women. This analysis found that more than 20 percent exceeded their maximum allowable weights and that this was associated with an increased cost of $22.8 million per year for medical care and lost workdays (especially among men). Unfortunately, the statistics on visits to military clinics for weight-related matters do not provide a complete picture. Military personnel are likely to enroll in commercial weight-reduction programs or to self-treat with supplements or over-the-counter medications rather than call attention to their weight, which invites possible disciplinary action or separation from the service with loss of benefits.

Diabetes, hypertension, and ischemic heart disease accounted for less than 1 percent of the visits made to ambulatory care clinics by active duty personnel in 1998. Taken together, all visits for “endocrine, nutritional, and metabolic diseases and immune disorders” and “diseases of the circulatory system” accounted for 4.5 percent of the total visits (in contrast, musculoskeletal disease and injuries/poisonings accounted for 26 percent and 16 percent of all visits, respectively). Thus, since the military is made up predominately of young, healthy individuals who exercise with some regularity, it appears that they are far more likely to suffer musculoskeletal injuries than they are to present health problems associated with obesity.

The Impact on Weight-Loss Behavior and Disordered Eating

Eating disorders have been widely studied among civilian women and among select groups of men (e.g., athletes, wrestlers). Gross disturbances in eating behavior characterize the conditions of anorexia nervosa currently seen in 1 to 2 percent of females in the general population, and bulimia nervosa, which has a prevalence of 1 to 3 percent in this population. Both disorders have a female-to-male ratio of occurrence of 10:1. Another category of eating disorders, known as not otherwise specified (NOS), has been reported in the literature to occur in 3 to 35 percent of the population.

The need to maintain weight-for-height and body composition standards does place pressure on military personnel, particularly those who may find themselves in more sedentary occupations after completing initial entry and advanced individual training. The military policy of testing personnel annually or semi-annually can lead to undesirable and potentially unhealthy practices. For example, Peterson and coworkers (1995) examined the incidence of bulimic weight-loss behaviors in individuals in a military weight-management program, a civilian weight-loss program, and military personnel not in a weight-loss program. Military personnel in a weight-management program engaged in significantly more bulimic behaviors than either of the other two groups. Behaviors such as vomiting, strenuous exercise, and use of saunas or steam rooms was four times more common in those assigned to the military weight-management program. These results are more notable in that this group of individuals was predominantly male (65 percent).

In a series of studies of Navy personnel and of military women in all services, McNulty used the Stanford Eating Disorders Questionnaire with 706 active-duty Navy nurses (McNulty, 1997a), 1,425 active-duty Navy men (23.7 percent officers and 76.3 percent enlisted men, McNulty, 1997b), and 1,278 active-duty women in the Army, Navy, Marine Corps, and Air Force (McNulty, 2001).

The existence of eating disorders was found to be wide-spread in the Navy nurses, even among normal-weight women within the standard of 30 percent body fat. The prevalence of bulimia nervosa was 12.5 percent in this population, more than six times the prevalence reported in the civilian literature (McNulty, 1997a). Among the top five reasons given by these women for engaging in these practices were: being overweight, command morale, and maintaining the Navy fitness standards.

Among Navy men, 50.1 percent of the men across all ranks were classified as having an eating disorder (6.8 percent bulimic, 2.5 percent anorexic, and 40.8 percent NOS). While the use of diuretics, vomiting, diet pills, laxatives, and fasting all had a 2 to 4 percent prevalence under normal conditions (binge eating at 14 percent), these behaviors increased to a prevalence of 14 to 15 percent at the time of weigh-ins and fitness testing (binge eating at 26 percent). The top four reasons for engaging in these behaviors were: feeling overweight, rotating shifts, shipboard assignments, and no time allowed for physical fitness except during off-duty hours (McNulty, 1997b).

In another study focused on women in all branches of the service (McNulty, 2001), data were gathered from 235 Army women, 443 Navy women, 355 Air Force women, and 245 Marine Corps women. For the combined sample of 1,278 service women, the prevalence of eating disorders was 1.1 percent for anorexia nervosa, 8.1 percent for bulimia nervosa, and 62.8 percent NOS; 28 percent reporting normal eating. Marine Corps women scored significantly higher for all disorders than women in other service branches, although they had the lowest reported percent body fat (91.3 percent of Marine Corps women had body fat less than 26 percent, compared with 60 percent of Army women, 69 percent of Navy women, and 67 percent of Air Force women). Of the Marine Corps women surveyed, 22.3 percent reported being amenorrheic, compared with 10.2 percent of Army women, 9.9 percent of Navy women, and 7.4 percent of Air Force women. The prevalence of use of various purging behaviors across the services are shown in Table 2-5. The top five reasons given for engaging in these types of behaviors were: competitiveness for advancement, concern for weight, being forced into a weight-control program, being harassed by supervisors for weight, and for Marine Corps women—lack of availability of low-fat meals. Clearly, these types of behaviors, coupled with the high prevalence of amenorrhea, could have significant long-term health implications for military women.

TABLE 2-5

Percent of Military Women Using Purging Behaviors to Meet Weight/Height Standards.

The Impact on the Loss of Personnel

The impact of body-fat standards on the military also can be assessed in terms of the separation of personnel. In 2002, almost 1.4 million men and women served on active duty in the four military services. The data of Lindquist and Bray (2001) suggest that 54 percent of active duty personnel are in danger of being assigned to a weight-control program, and some of these may be at risk of separation from the service due to overweight (based on self-reported BMIs). As shown in Table 2-6, over 4,600 individuals were discharged from the military for being overweight in 1999, but the numbers show a steady decline. (A large part of the decline is due to the Navy's decision to halt discharges for overweight. Navy personnel who fail to meet the standards are now allowed to serve out their current term of enlistment, but they are not permitted to re-enlist.) In 2002, total early separations for persistent failure to meet weight and body composition standards totaled just over 1,400 individuals. This is approximately 0.1 percent of the active duty force of 1.4 million personnel and represents a lost investment of approximately $57 million (in 1995 dollars), based on an estimated cost of recruitment and training of $40,283 per person (DOD PEC, 1997).

TABLE 2-6

Number of Military Personnel Separated for Failure to Meet Weight and Body Composition Standards.

Army

The Army program, “Weigh to Stay,” is managed by physical fitness trainers who must complete a course on weight loss and weight-control counseling. The Army also runs a number of hospital weight-loss and weight-management programs that are overseen by physicians as part of preventive medicine research efforts. The Hawaii-based program is highly innovative in its reliance on behavior modification and use of the Internet to maintain support of individuals at remote locations (James LC et al., 1997; James et al., 1999b). Monthly weigh-ins are required, and those who fail to make satisfactory progress (loss of 3 to 8 lb/mo) for 2 consecutive months can face separation. Exemptions from the program are granted for prolonged illness, pregnancy (up to 180 d postpartum), hospitalization, or a medical profile waiver (U.S. Army, 1987).

Navy

According to the Physical Readiness Program (U.S. Navy, 2002) the Navy's Command-Directed Physical Conditioning Program (CDPCP) is required for all individuals who fail the physical fitness test or who do not meet body fat standards. It is a 6-month program managed by a command-trained, physical-fitness coordinator (an enlisted person who has undergone 2.5 days of training). The program includes mandatory supervised exercise three times per week. Each individual who exceeds body-fat standards is issued a self-study nutrition and weight-control guide. A more rigorous, second phase program is the Bureau of Medicine-Approved Weight Management Program, an intensive 2-week outpatient program that requires the commanding officer's endorsement and 6-months prior participation in the CDPCP. Individuals with three fitness or body fat failures are not eligible (three failures in 4 years results in administrative action and although individuals are no longer separated from the service, they are not permitted to reenlist and are not eligible for promotion for the duration of their enlistment term). Successful completion of the Bureau of Medicine program and 1 year of follow-up in which progress continues toward meeting body fat standards result in a clear record. The Navy also conducts a 2-day course on recipe modification for mess specialists. The Navy has some innovative, small-scale weight-control programs to which selected individuals can be assigned. These include a 10-week program on nutrition, behavior modification, and exercise, with monthly support-group follow-up at the Norfolk Navy Environmental Health Center; a shipboard weight-control program (Dennis et al., 1999); and a program at San Diego Naval Medical Center that is regarded as a model for programs used at other locations (Carlson and Burman, 1984; Trent and Stevens, 1993, 1995). The challenge for the Navy has been to devise a single program that would address the needs of personnel at diverse duty stations and that could be taught by minimally trained personnel (Hoiberg and McNally, 1991).

Marine Corps

The Marine Corps' physical fitness/weight-control program, “Semper Fit,” similar to that of the Army, is managed by physical fitness trainers. Diet counseling is administered by self-study or by a dietitian if the individuals are close to an installation with an available dietetic service. Individuals who fail to meet the body fat standards and who do not receive a medical waiver are enrolled for an initial period of 6 months. If the individual is progressing but has not yet reached the target weight or percent body fat at the 6-month point, he or she may be allowed to continue for another 6 months. If after reaching the goal, the individual fails again during the rest of his or her career, he or she is allowed another 6 months to achieve compliance or face separation (USMC, 2002).

Air Force

The Air Force Weight and Body Fat Management Program (WBFMP) operates from a health and wellness center (HAWC) located on each base, which is responsible for assessment of weight, body fat, fitness, and data recording. Personnel who exceed the body-fat standards undergo clinical, laboratory, and psychological assessment to determine their qualification for the WBFMP. Those deemed unqualified are sent to an appropriate practitioner for care. The program consists of three phases. Medically cleared personnel are admitted to a 3-month initial program that provides counseling on diet and behavior modification by an Air Force dietitian or other authorized medical personnel, as well as exercise instruction provided by the HAWC staff. All individuals assigned to the program must attend a series of four classes concerning diet, behavior modification, and exercise. Personnel enrolled in the initial program are not penalized by administrative actions during the 3-month enrollment, although they are restricted from some professional activities. Personnel who meet their weight/body fat standard after completion of the 3-month program proceed to Phase II, a 6-month maintenance/monitoring program. Following successful completion of Phase II, the individual's WBFMP records are expunged. Personnel who fail to meet their goal within the first 3 months of the initial program are enrolled in Phase I, a more intense weight-management program in which monitoring is conducted monthly and the individual is subject to significant administrative restrictions relating to assignments, training, and promotions. Each Air Force installation has the authority to select programs approved by the Major Command dietitian for use in counseling on diet and exercise (USAF, 2002), for example, “The Sensible Weigh” or “Shape Your Future Your Weigh.”