Police Body Composition
1
Journal of Exercise Physiologyonline
(JEPonline)
Volume 11 Number 6 December 2008
Managing Editor
Tommy Boone, PhD, MPH
Editor-in-Chief
Jon K. Linderman, PhD
Review Board
Todd Astorino, PhD
Julien Baker, PhD
Tommy Boone, PhD
Larry Birnbaum, PhD
Lance Dalleck, PhD
Dan Drury, DPE
Hermann Engals, PhD
Eric Goulet, PhD
Robert Gotshall, PhD
M. Knight-Maloney, PhD
Len Kravitz, PhD
James Laskin, PhD
Derek Marks, PhD
Cristine Mermier, PhD
Daryl Parker, PhD
Robert Robergs, PhD
Brent Ruby, PhD
Jason Siegler, PhD
Greg Tardie, PhD
Chantal Vella, PhD
Lesley White, PhD
Ben Zhou, PhD
Official Research Journal
of the American Society of
Exercise Physiologists
(ASEP)
ISSN 1097-9751
Body Composition
A LONGITUDINAL OBSERVATION OF POLICE: BODY
COMPOSITION CHANGES OVER 12 YEARS WITH GENDER AND
RACE COMPARISONS
ROBERT BOYCE1, GLENN JONES2, CAMERON LLOYD1, EDWARD
BOONE3
1
University of North Carolina at Wilmington, NC, USA
Charlotte Mecklenburg Police Department, Charlotte, NC, USA
3
Virginia Commonwealth University, Richmond, VA, USA
2
ABSTRACT
Boyce RW, Jones GR, Lloyd CL, Boone EL. A longitudinal study of
police: Body composition changes over 12 years with gender and race
comparisons. JEPonline 2008;11(6):1-13. Body composition changes
over time have implications for police officer selection, physical
performance, and health. The major purposes of this research were to
1) report the changes in body composition from initial-recruit to after 12
years service and 2) compare differences between genders and races,
and among low to high body composition groups. Sample included 327
police; 30 females (13 black, 17 white), 297 males (41 black, 238 white,
and 18 others). Average number of years between tests was 12.5±2.0
years. Mean age at initial-recruit was 24.6±3.4 years and at in-service
was 37.1±3.7 years. The dependent variables included body mass,
percent body fat, fat mass, and lean mass. Each male variable was
divided into quintiles based on initial-recruit measurement, ranging from
lowest (group 1) to highest (group 5).
Body composition variables
increased significantly regardless of gender or race. Black males
increased significantly more than white males. Black females gained
considerably less body mass than reported in other studies. Males
gained significantly more lean mass than females. Low to high body
composition groups had relatively consistent changes over time. In the
percent fat groups the lowest group gained most and highest gained
least. Percent becoming obese was markedly greater in highest percent
fat group. Through this longitudinal observation, exercise physiologists
are given insight into an on-going police physical fitness program and its
impact on body composition of legally protected groups of sex and race.
Key Words: Body Weight, Body Fat, Sex Differences, Race Differences,
Obesity.
Police Body Composition
2
INTRODUCTION
The occupation of police officer is primarily sedentary, though mentally challenging, with occasional
periods of maximal exertion (1). The physical demands of this job are often inadequate to maintaining
necessary physical fitness to perform the infrequent but possibly life-saving tasks (2). Low levels of
physical activity promote increases in weight, body fat and potential health issues (3, 4). Weight gain
can also account for decline in an officer's physical performance (1) and is associated with decreases
in cardiopulmonary fitness (5). Furthermore, those in the highest quartile of body weight (6), as well
as overweight and obese individuals, have been found to gain more weight over time (7, 8).
Therefore, heavier and obese officers may be decreasing in their ability to physically perform their job
at a higher rate than their lower weight counterparts.
Reduction in physical performance due to weight gain may be ameliorated, because weight gain is
comprised of both lean and fat mass (9). Lean mass gain is associated with increases in muscular
strength (10, 11). Also, the rate of weight gain may be related to the subject's starting weight and the
composition of the tissue gained (12).
Few longitudinal studies, over one year, have been conducted on changes in body composition of
police (1, 13-15), and no longitudinal work was found that included black officers or followed fat and
lean mass changes. No other studies were found on female officers. Also, no studies were found
that compared officers at recruitment with low body composition values with those of high values to
their eventual body composition status as an in-service officer.
The need exists to investigate police body composition changes over time. Police officers have a
specific socio-economic and occupational status, allowing for comparisons with other groups to study
the numerous factors influencing weight gain, including interactions between fat and lean mass.
Furthermore, administrators gain insight regarding officer selection to ensure optimal physical
performance of duties (16, 17) and design programs to foster weight management and health.
This report describes and compares body composition and weight changes, including gender and
race comparisons, within the Charlotte Mecklenburg, North Carolina Police Department from entrance
into recruit school to in-service status approximately 12.5 years later. Also, low to high body
composition groups of male officers, determined at the initial week of recruit training, were compared
to determine changes within and among groups.
METHODS
Subjects
The sample included 327 police officers, 30 females (13 black, 17 white) and 297 males (41 black,
238 white and 18 other) participating in recruit classes between 1990 and 1995. Ninety-nine percent
of the in-service fitness tests were conducted between the years of 2003 to 2006. Mean values with
standard deviations are provided in the text as mean±SD. The mean age at initial-recruit test was
24.6±3.4 years and for in-service was 37.1±3.7 years. The average number of years between tests
was 12.5±2.0 years. There were no significant difference between genders and races for age and
time between the two tests. Officers were primarily college-educated and their socio-economic status
ranged from lower-middle to upper-middle class. An officer's physical capacity was a consideration at
hiring. However, while physical fitness tests were a factor in selection for some recruit classes, this
was not consistent over the duration of this study.
Police Body Composition
3
Procedures
Physical fitness test records were obtained from the Charlotte Mecklenburg Police Department, a
large metropolitan police department in the southeastern United States of America. Body mass and
percent body fat scores were retrieved for officers in the 1990 to 1995 recruit classes. Officers' recruit
scores were paired to their most recent scores on the 2006 in-service fitness records. Scores for
officers in the recruit records that were not in the in-service records were discarded.
Emphasis was placed on encouraging recruits to continue healthy exercise habits following
completion of the 16 - 20 week recruit training. The same physical fitness coordinator, certified by the
American College of Sports Medicine (ACSM), administered tests over the study period. Sworn
officers (in-service) received an annual fitness test. The physical fitness coordinator suggested
nutritional and/or exercise programs for officers, following evaluations and when requested.
Included in the physical fitness test battery for recruits and sworn officers was body mass and percent
body fat, using a skinfold caliper (18). The skinfold test utilized a three-site formula. The sites for
males were chest, abdomen, and thigh. The sites for females were triceps, suprailiac, and thigh (19).
The testing protocol was based upon ACSM’s Guidelines for Exercise Testing and Prescription (20).
Tests were administered the first week of recruit training (initial-recruit test). Body mass and percent
body fat tests remained consistent during the study period. Lean mass percentage was calculated
from mean body mass and lean mass values with the formula: (lean mass/body mass)*100.
The University of North Carolina at Wilmington Institutional Review Board approved this study
following the Office of Human Research Protection Requirements. Because this research involved
existing and unidentifiable data, it was exempt from applicable human subject regulation. The tests
and measurements were required as a part of conditions of their employment.
Statistical Analyses
The Statistical Package for Social Sciences (SPSS, Inc) version 15.0 was used to analyze data.
Paired-sample t tests compared mean differences between initial-recruit to in-service test for age,
body mass, fat percentage, fat mass and lean mass. Analysis of variance (ANOVA) procedures
compared gender and race (black/white) in the amount of change from initial-recruit to in-service tests
in these same variables. Fisher exact tests were used to test for differences in the percentage that
were obese between initial recruit to in-service tests, differences between gender and race groups at
initial-recruit and in-service tests and differences in amount of change between gender and race
groups from initial-recruit to in-service tests. Obesity was defined as ≥ 25% body fat for males and ≥
30% body fat for females.
High to low groups within each variable were tracked and changes among groups were compared.
The male sample was subdivided into 5 equal groups based on initial-recruit measurements. The cut
point for the 5 male groups corresponded to the 20th, 40th, 60th and 80th percentiles. Group 1
represented the lowest values progressing to group 5, the highest. Gender or race comparisons were
discontinued as further dividing the female, n=30, and black race, n=41, into smaller groups would
have considerably weakened comparisons. Analysis included paired-sample t-tests to test mean
differences between initial-recruit and in-service evaluation for each group. ANOVA and Tukey
multiple comparison procedures were used to compare amount of changes among groups from initialrecruit to in-service tests for each variable.
Police Body Composition
4
RESULTS
Table I provides the results of body
composition tests at initial-recruit and after
12.5
year-service
with
comparison
between races and genders. Body mass
and lean mass were significantly higher in
males than females and females had
significantly higher percent body fat than
males for both initial-recruit and in-service
tests. No differences were found in the
amount of fat mass between genders.
However, this may be due to the low
number of females that participated in the
study.
The percent of officers classified as obese
was low for all genders and races at the
initial-recruit evaluation with both gender
and race groups significantly (p< 0.05)
increasing in obesity percentage by the inservice test. Values from initial-recruit to
in-service were: Black female, 8% to 23%; white female, 6% to 18%; black males, 5% to 22%; and
white males, 5% to 18%. No significant differences in the percentage that were classified as obese
were found between genders or between races at either of the testing periods or in amount the
groups changed from initial-recruit to in-service.
Table I, comparing races, found no significant
differences in initial-recruit and in-services
tests for females. However, lean mass was
significantly higher in black males than white
males at initial-recruit test and in-service test.
Body mass was significantly higher in black
males than white males at the in-service test.
No significant differences were found between
black and white males in percent fat and fat
mass.
Body mass, percent body fat, fat mass and
lean mass significantly increased (p ≤ 0.001)
from initial-recruit to in-service tests within
genders and races. Twenty percent of the
officers gained at least 18.8 kg with
comparable values for females vs. males
being 11.4 kg vs. 19.1 kg and black vs. white
males being 23.4 kg vs. 18.0 kg and black vs.
white females being 13.1 kg vs. 11.4 kg.
Police Body Composition
5
Table 2. Comparisons of changes in body composition from initial-recruit to 12.5 year-service
in police officers between genders and races
Change Variable
Body Mass (kg)
Fat %
Fat Mass (kg)
Lean Mass (kg)
Race
Black
White
Total
Black
White
Total
Black
White
Total
Black
White
N
13
17
30
13
17
30
13
17
30
13
17
Female
Mean
SD p-valueR
9.2
6.7
6.2
5.5
0.194
7.5
6.1
5.7
3.2
4.6
5.1
0.511
5.1
4.3
6.0
3.8
4.2
4.2
0.230
5.0
4.1
3.2
3.5
2.0
2.7
0.318
2.5
3.1
N
41
246
Male
Mean SD
16.5
8.9
11.7
9.1
p-valueR
0.002
287
41
245
12.3
6.6
4.5
4.8
9.3
6.1
0.007
Total
30
287
= p-value for race comparison
G =p-value for gender comparison
ANOVA Comparison between genders: *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001
6.6
7.2
5.4
0.683
**
6.3
5.5
4.7
0.193
0.029
5.7
4.9
**
**
4.8
6.1
6.2
0.003
286
41
246
**
9.2
4.8
4.8
0.010
286
41
245
p-valueG
*
0.001
***
R
Table 2 further compares genders in amount of change in these variables from initial-recruit to inservice tests. No significant differences were
found between males and females in the
amount gained in percent fat and fat mass.
However, males gained significantly more
body mass and lean mass than females.
Average gain per year in body mass was 1.0
±0.7 kg for males and 0.6±0.5 kg for females.
Average gain per year for lean mass was 0.4
±0.4 kg for males and 0.2±0.2 kg for females.
Body mass gain attributed to lean mass was
higher in males, 46%, than females, 34%.
Percent of body mass gain that was lean
mass was: Black female, 35%, white female,
33%, black male, 44%, white male, 47%.
Table 2 also compares changes in body
composition between races from initial-recruit
to in-services tests. No differences were
found between black and white females in
any body composition variables. However,
black males gained significantly more than
white males from initial-recruit to in-service
tests in body mass, percent fat, fat mass, and lean mass. The body mass gain attributed to lean
mass was higher in white males, 47%, than black males, 44%. No race differences were found in the
percentage that became obese.
Police Body Composition
6
Figure 1 compares the changes in body mass among low to high body mass groups of male police
officers from initial-recruit to in-service over 12.5 years. Body mass significantly (p ≤ 0.001) increased
from initial-recruit to in-service tests in all
groups. However, change among groups
was consistent as there were no significant
differences in amount of change among
groups. This same pattern occurred in fat
mass with no significant differences found
among groups with gain in fat mass of the 5
groups ranging from 6.7±7.4 kg to 6.1±7.0 kg.
Figure 2 compares the changes in percent
body fat among low to high percent body fat
groups of male police officers from initialrecruit to in-service over 12.5 years.
Percent body fat significantly (p ≤ 0.001)
increased in all low to high percent body fat
groups. A different pattern occurred in male
mean values as opposed to body mass. The
lowest percent fat group gained the most and
the highest percent fat group gained the least, with a significant (p < 0.05) difference between groups
4 and 5 and groups 1, 2 and 3.
Figure 3 compares the changes in lean mass among low to high lean mass groups of male police
officers from initial-recruit to in-service over 12.5 years. Lean mass also increased in all groups. The
higher lean mass groups, 4 and 5, tended to gain less lean mass than the lower lean groups, 1, 2,
and 3 with group five gaining significantly less lean mass than group 3 (p < 0.05). Relative changes
of lean body mass from lowest to highest groups remained consistent, as seen in all targeted body
composition variables.
Figure 4 depicts the change in percent of male officers who were obese from initial-recruit to inservice tests over 12.5 years among low to high percent fat groups. The highest percent fat group
had a marked and significantly (p ≤ 0.001) greater mean difference in the percentage that became
obese.
DISCUSSION
This unique longitudinal data of changes in body composition with a large sample size of police
officers revealed the following. Targeted body composition variables increased significantly
regardless of gender or race. Gender and racial differences occurred in the amount of body mass
change. Black females gained considerably less mass than reported in general population studies.
Black males increased in targeted variables significantly more than white males except the percent
that become obese. Gains were relatively similar between genders in percent fat, fat mass and
percent that become obese, with males gaining significantly more lean mass than females. Body
composition groups (low to high) revealed a relatively consistent change over time among all groups.
However, in the percent fat groups, the lowest group gained the most and the highest gained the
least. Also, the highest percent fat group showed a marked increase in the percent that became
obese.
Police Body Composition
7
Table 1. The results of body composition tests at initial-recruit and after 12.5 yearservice with comparisons between races and genders
Initial Recruit:
Female
Mean SD
24.9
3.7
23.9
2.5
Age (yrs)
Race
Black
White
N
13
17
Body Mass (kg)
Total
Black
White
30
13
17
24.3
59.3
57.8
3.1
7.9
6.6
Fat %
Total
Black
White
30
13
17
58.4
19.8
20.5
7.1
4.4
5.0
Fat Mass (kg)
Total
Black
White
30
13
17
20.2
12.0
12.0
4.7
4.2
3.7
Lean Mass (kg)
Total
Black
White
30
13
17
12.0
47.3
45.8
3.8
4.7
4.8
Total
30
46.4
4.7
Age (yrs)
Race
Black
White
N
13
17
Body Mass (kg)
Total
Black
White
30
13
17
37.0
68.5
64.0
3.4
11.8
5.0
Fat %
Total
Black
White
30
13
17
66.0
25.5
25.1
8.7
6.1
6.4
Fat Mass (kg)
Total
Black
White
30
13
17
25.3
18.0
16.2
6.1
7.0
4.7
Lean Mass (kg)
Total
Black
White
30
13
17
17.0
50.5
47.8
5.8
5.9
4.8
p-valueR
Male
SD
3.6
3.5
N
41
238
Mean
25.1
24.5
279
41
238
24.6
84.9
82.0
3.5
10.3
12.9
279
41
238
82.4
13.2
14.6
12.6
6.0
5.7
279
41
238
14.4
11.3
12.4
5.8
5.4
6.4
279
41
238
12.2
73.6
69.6
6.3
9.4
8.7
279
70.2
8.9
N
41
238
Mean
38.0
37.0
Male
SD
3.6
3.8
279
41
238
37.1
101.4
93.4
3.8
14.0
15.9
279
41
238
94.6
19.8
19.0
15.9
5.8
5.9
279
41
238
19.1
20.6
18.4
5.9
8.1
8.5
279
41
238
18.7
80.8
75.0
8.5
8.7
9.5
0.399
0.331
0.570
***
0.000
***
0.292
0.398
p-valueR
0.000
0.157
0.992
Female
Mean SD
37.5
3.2
36.6
3.6
0.626
0.167
0.712
In-Service:
p-valueG
p-valueR
0.750
0.007
0.495
**
0.000
p-valueR
***
p-valueG
0.125
0.168
0.770
0.003
0.859
**
0.000
***
0.000
***
0.420
0.398
0.130
0.188
Total
30 49.0
5.4
279 75.9
G = p-value to compare genders
R = p-value to compare races
ANOVA Comparisons between races and genders: **p ≤ .01; ***p ≤ .001
0.247
0.000
9.6
***
0.000
***
Police Body Composition
8
Strengths and Potential Weaknesses of This Study
The primary strengths of this study in comparison to other police studies were the number of subjects,
the duration, variety of body composition factors targeted, and the gender and race (black and white)
comparisons. It is the first study, to our knowledge, in the continental United States, following officers
for more than three years. Other police studies included only males (1, 14, 15). This study is unique
for including females, contrasting racial and gender differences.
The low number of female subjects is a potential weakness. However, the increasing role of females
in police and this study's findings, that contradict existing general population literature, underline the
importance of including them. Also, this study involved only one regional police department, albeit a
large one and the results may not extrapolate to other samples.
Consistent data collection by a single certified test administrator, a professional exercise physiologist,
strengthened this study. The test administrator used skinfold measurements during all test periods,
as opposed to BMI (21). However, inherent errors exist in skinfold measurements, such as when
subjects are extremely obese or lean (20, 22) or have large amounts of visceral fat (23).
There are also racial variations in skinfold formulas and obesity cut off points (24). It is reported that
fat free body density is higher in blacks than in whites (25). This can result in an over estimation of
body fat percentages and obesity percentages in blacks. There are racial differences in the
distribution of subcutaneous fat between blacks and whites which can create errors when using
generalized skinfold formulas in predicting the percent body fat between blacks and whites.
However, it is still unclear, whether generalized prediction equations yield inaccurate results for
blacks (25). Research has shown that the generalized skinfold-thickness equations of Jackson and
Pollack (26, 27) are appropriate for estimating the percent body fat of black men and women.
However, other researchers have reported errors when using generalized formulas to estimate the
body composition of black samples and recommend the development of race specific equations (28).
As a result of these conflicting views further cross validation of race specific equations has been
recommended (25) and these race specific cross validation studies need to be conducted within
specific occupations such as police officer.
Another reason for the need to cross validate the skinfold equations is that socio-economic status and
environmental background is another confounding variable which can effect fat free body density
(25), thus impacting occupational body composition studies. The job characteristics and the
department selection process in the police department created a level of homogeneity in regards to
education level and socio-economic status of the sample. Further research is recommended using
DXA to estimate percent body fat as it bypasses the need to use skinfold formulas.
Further research is needed in regards to body composition of police officers in relation to body mass
index. Prior to the collection of the data utilized in this research, the Charlotte-Mecklenburg Police
Department made the decision to refrain from gathering body height data as part of the physical
fitness testing program. This was a result of legal proceedings within the profession challenging the
minimum height hiring requirement for police officers. Consequently, no height data was available for
this longitudinal observation.
Comparisons to Other Research
Our findings were similar to other studies, police (1, 13-15) and non-police (6, 29, 30) in that all
gender and racial groups gained body mass. In police, male body mass increased in our study, 1.0
kg per year, which was higher than the two studies conducted on Finnish officers, approximately .8 to
.5 kg per year (1) but less that than a Hawaiian police study (15) 1.8 kg per year. No body
Police Body Composition
9
composition studies on female police were found in the literature which negated comparisons with the
current female sample in relation to body mass gain per year.
Non-police studies comparing white men and women in Finland (31) and Holland (32) and the United
States (33), found that men gained more body mass than women, which supports our study. The
Finnish men had more than twice the risk of major body mass gain than women. Conversely, other
United States studies found women gained more than men (30, 34) and major body mass gain was
nearly twice as high in women than men (30).
Our results deviate considerably from other racial observations in that our black females gained much
less body mass than the black females in these other studies. In these other non-police studies,
black women had greater body mass gain than all other groups with a magnitude of approximately
1.5 to 2.5 times that of white females (6, 33, 35). Our black female officers gained only approximately
60% of the body mass reported by black females in the CARDIA studies (6, 35) and they gained less
body mass per year than black and white males in our study. Other research suggests body mass
gain (34) varied more in black than white females especially at the 90th body mass percentile.
However, the police physical selection process reduced variability in body mass profiles as our
subjects started with comparatively lower body mass.
These differences in body mass gain compared to other samples may have connections to socioeconomic status and the selection process. Our subjects had middle to higher income status and
were college educated. Only 5% were classified as obese at hire. Negative associations have been
observed with education (4, 36-39), employment grade (40) and income (41) with BMI, and also with
education and increases in body mass (6). However, in a longitudinal study, black men showed no
differences between body mass gain and education level (6).
Further research is needed to
determine why the black male officers in our study gained more body mass than the black females
and as to why they had higher body mass gains per year than any other research we found, including
both police and general populations (6, 33, 35).
In cross-sectional studies, black females had higher mean BMI values over that of white females at
comparable education and income levels (38) and a negative association with education and body
mass status was seen in white women but not in black women (36). Another cross-sectional study,
adjusting for baseline BMI and multiple demographic, social and behavioral variables, found BMI
differences in black and white female were not reduced (42). The results of our longitudinal study
were dissimilar enough from these to indicate a need for more research on female police.
Our results support other evidence that lean and fat tissues are interdependent (9, 43, 44). Body
mass increases include both fat and lean. As in the literature, lean mass increased most in males (9).
No other longitudinal works were found comparing racial differences in lean mass gain related to
body mass increase. The relationship of lean body mass to body mass gain requires further research
regarding its role in performance of physical duties. Nearly half the total body mass gain in our male
officers and a third in our female officers was lean mass. A review of over-feeding studies reported
the mean composition of body mass gain was 44% lean (45), which was within the values of our
study: 34% for females and 46% for males.
Our study found no significant differences between racial groups for the percent that were obese at
recruitment or in-service within either gender. This outcome goes against population surveys that
overwhelmingly report black females have considerably higher obese rates, as measured by BMI,
than white females (29, 36, 37, 46, 47).
Police Body Composition
10
When considering the male officers in five low to high body composition groups, as determined at
recruit training, the highest groups remained highest and the lowest groups the lowest after 12 years.
This has two primary implications. First, as no significant differences were found in the amount of
body mass or fat mass gained, increased health risks related to body mass gain (33, 48, 49) may be
equal among the groups. Second, obesity, with its implications for cardiovascular health and
organizational cost risks (21, 50), became considerably more prevalent in the highest percent fat
group because they were closer to obesity levels when hired. Further longitudinal research, involving
low to high body composition groups, is suggested to investigate the affect of body mass gain and
level of percent fat upon health risks and organizational costs. In addition, research is warranted
concerning the tendency for the lowest percent fat groups to gain the most and the highest, the least.
CONCLUSIONS
The results of this study have multiple implications for police and related occupations. Clearly,
officers will, on average, increase in body composition values over the first decade of employment.
Also, body composition levels upon hire do not seem to greatly affect the amount of change over
time. Since job performance and health are connected to body composition factors, and those factors
are themselves, interdependent, it is unrealistic to simply require an officer to avoid body mass gain.
Exercise physiologists and health professionals can play an essential role in organizations by
identifying the optimal body composition for this occupation and its relationship to officer selection,
training, job performance, and health.
Address for correspondence: Boyce RW, PhD., Department of Health and Applied Human
Sciences, University of North Carolina at Wilmington, Wilmington, NC, USA 28403. Phone (910) 9627824; FAX: (910) 962-7073; Email: boycer@uncw.edu.
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