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The Overweight Athlete

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The Overweight Athlete
Chapter 35
The Overweight Athlete
MELINDA M. MANORE
Introduction
For the sport medicine team, the overweight
athlete can present numerous challenges. First,
the type of athlete who wants or needs to lose
weight can vary dramatically, from a small
female participating in a lean build sport (gymnastics, track and field, figure skating) to a large
male participating in a strength or power sport
(weightlifting, heavy weight wrestling). Some of
these athletes may also participate in sports that
require ‘making weight,’ which adds a unique
challenge to any health professional guiding
them through the weight-loss process. These athletes may not be ‘overfat or overweight’ according to normal criteria, but may be considered
heavy for their sport or for the weight category in
which they must compete. To further complicate
the weight-loss process, some athletes participate in sports in which they are judged on both
performance and appearance. This can add pressure to reduce body weight lower than optimal
for good health and performance. Second, the
weight-loss programme needs to provide adequate energy so that exercise training can still
occur. The diet cannot be too restrictive in energy
without the athlete running the risk of injury, loss
of fat-free mass (FFM), poor performance, feelings of deprivation, and eventual failure. Thus,
adequate time needs to be allotted for weight loss
to occur. Aerobic and strength training may also
need to be added if they are not already a part of
the athlete’s normal training programme.
Finally, the weight-loss programme needs to
provide a strong educational component. The
athlete needs to be taught good nutritional, exercise and behavioural techniques for long-term
weight maintenance. Without an educational
component, the athlete is susceptible to the many
fad diets, diet products, and weight-loss drugs
that frequently hit the consumer market. With
the emphasis placed on physical appearance in
Western society, dieting can become obsessive.
The athlete is not immune to this pressure. In
fact, they are pressured on two fronts: their sport
and society. This pressure can lead to desperate
means of weight loss and an eventual eating
disorder.
This review will briefly outline the principles
and components of energy balance that need to
be considered before placing an athlete on a
weight-loss programme. Specific methods for
determining energy balance in an athlete will
also be reviewed. Finally, practical applications
and guidelines for determining the weight-loss
goal and approaches to gradual weight loss will
be given. For individuals working with athletes
in weight-category sports, the effects of rapid
weight loss on health and performance has been
addressed elsewhere (Steen & Brownell 1990;
Horswill 1992, 1993; Fogelholm 1994). Other
excellent reviews are available on the effect of
weight loss on sport performance (Wilmore
1992a), the techniques used in different sports
(Fogelholm 1994; Burke 1995), the effect of
weight loss on health and metabolism (Brownell
et al. 1987), and the role of dieting in eating disorders (Wilmore 1991; Sundgot-Borgen 1993, 1994;
469
470
practical issues
Beals & Manore 1994) and menstrual dysfunction (Dueck et al. 1996). Part 4 of this book gives
more specific information about the weight and
nutrition concerns of different sports, particularly weight-category sports.
Energy and nutrient balance
The classic energy balance equation states that if
energy intake equals energy expenditure then
weight is maintained; however, this equation
does not allow for changes in body composition
and energy stores (Ravussin & Swinburn 1993).
The maintenance of body weight and composition over time requires that energy intake equals
energy expenditure, and that dietary intakes of
protein, carbohydrate, fat and alcohol equal their
oxidation rates (Flatt 1992; Swinburn & Ravussin
1993). If this occurs, an individual is considered
to be in energy balance and body weight and
composition will be maintained.
This approach to energy balance is dynamic
and allows for the effect of changing energy
stores on energy expenditure over time. For
example, after a short period of positive energy
balance, the extra energy would cause weight
gain (of both fat and lean tissues). However,
the larger body size would cause an increase
in energy expenditure that would eventually
balance the extra energy consumed. Thus,
weight gain can be the consequence of an initial
positive energy balance, but can also be a mechanism whereby energy balance is eventually
restored. Conversely, weight loss must reverse
this process. If body fat is to be lost, energy intake
must be less than expenditure, and fat oxidation
must exceed fat intake (Westerterp 1993).
Nutrient balance
The alteration of energy intake and expenditure
is just one part of the energy balance picture.
Changes in the type and amount of nutrients
consumed (i.e. protein, fat, carbohydrate and
alcohol) and the oxidation of these nutrients
within the body must also be considered. Under
normal physiological conditions, carbohydrate,
protein and alcohol are not easily converted
to body fat (Abbott et al. 1988; Swinburn &
Ravussin 1993). Thus, increases in the intake of
non-fat nutrients stimulate their oxidation rates
proportionally. Conversely, an increase in fat
intake does not immediately stimulate fat oxidation, hence increasing the probability that dietary
fat will be stored as adipose tissue (Abbott et al.
1988; Westerterp 1993). Therefore, the type of
food consumed plays a role in the amount of
energy consumed and expended each day
(Acheson et al. 1984; Swinburn & Ravussin 1993).
Successful weight loss requires that an energy
deficit be produced (either through increased
energy expenditure and/or decreased energy
intake) and diet composition and oxidation be
altered (decreased fat intake and/or increased fat
oxidation through exercise) (Hill et al. 1993).
Carbohydrate balance
Carbohydrate balance is proposed to be precisely
regulated (Flatt 1992), with the ingestion of carbohydrate stimulating both glycogen storage
and glucose oxidation, and inhibiting fat oxidation (Fig. 35.1). Glucose not stored as glycogen is
thought to be oxidized directly in almost equal
balance to that consumed (Schutz et al. 1989;
Thomas et al. 1992). Thus, the conversion of
excess dietary carbohydrate to triglycerides does
not appear to occur to any large extent in humans
under normal physiological conditions (Acheson
et al. 1988; Hellerstein et al. 1991).
Protein balance
Like carbohydrate, the body alters protein oxidation rates to match protein intakes (Thomas et al.
1992). Once anabolic needs are met, the carbon
skeletons of excess amino acids can be used for
energy. The adequacy of both energy and carbohydrate intake dramatically affects this process.
Inadequate energy or carbohydrate intakes will
result in negative protein balance, while excess
intake of energy or carbohydrate will spare
protein (Krempf et al. 1993). Any excess dietary
protein or that made available through protein
the overweight athlete
Protein oxidation
(g.day–1)
150
100
50
0
0
50
100
150
100
50
(a)
1000
500
800
400
600
400
200
0
0
(b)
400
600
800
CHO intake (g.day–1)
200
200
100
0
(b)
100
200
300
400
CHO intake (g.day–1)
500
300
Fat oxidation
(g.day–1)
100
50
0
(c)
100
150
Protein intake (g.day–1)
300
1000
150
–50
0
50
0
200
200
Fat oxidation
(g.day–1)
150
0
0
200
Protein intake (g.day–1)
(a)
CHO oxidation
(g.day–1)
200
CHO oxidation
(g.day–1)
Protein oxidation
(g.day–1)
200
471
50
100
Fat intake
150
100
0
0
200
(g.day–1)
200
(c)
100
200
300
Fat intake (g.day–1)
Fig. 35.1 High-carbohydrate diet: the relationship
between intake and oxidation of (a) protein, (b)
carbohydrate (CHO), and (c) fat for all subjects on day
7 of a high carbohydrate feeding period. — , regression
line for all 21 subjects; - - - , regression line for lean
subjects (䊊); · · · ·, regression line for obese subjects (䊉).
(a) Lean subjects: r = 0.79, P < 0.01; obese subjects:
r = 0.59, n.s. (b) Lean subjects: r = 0.74, P < 0.01; obese
subjects: r = 0.79, P < 0.01. (c) Lean subjects: r = 0.06,
n.s.; obese subjects: r = –0.08, n.s. From Thomas et al.
(1992), with permission.
Fig. 35.2 High-fat diet: the relationship between intake
and oxidation of (a) protein, (b) carbohydrate (CHO),
and (c) fat for all subjects on day 7 of a high fat feeding
period. — , regression line for all 21 subjects; - - - ,
regression line for lean subjects (䊊); · · · ·, regression
line for obese subjects (䊉). (a) Lean subjects: r = 0.78,
P < 0.01; obese subjects: r = 0.74, P < 0.02. (b) Lean
subjects: r = 0.32, n.s.; obese subjects: r = 0.14, n.s.
(c) Lean subjects: r = 0.78, P < 0.01; obese subjects:
r = 0.02, n.s. From Thomas et al. (1992), with
permission.
sparing may contribute indirectly to fat storage
by sparing dietary fat.
Figure 35.2 shows that as fat intake increases, the
oxidation of fat does not increase proportionately (Thomas et al. 1992). Thus, acute increases
in fat intake have little influence on fat oxidation.
For example, Jebb et al. (1996) overfed three lean
men by 33% of energy requirements for 12 days.
They found that carbohydrate and protein intake
Fat balance
Fat balance is not as precisely regulated as either
protein or carbohydrate balance (Flatt 1992).
472
practical issues
(grams per day) matched their oxidation rates,
while fat oxidation rates did not change significantly even though fat intake increased (fat
intake was 150 g · day–1 while fat oxidation was
only 59 g · day–1). The result was a 2.9-kg weight
gain in 12 days. Thus, excess energy eaten as
dietary fat is stored as triglycerides in adipose
tissue with little loss of energy (Acheson et al.
1984; Swinburn & Ravussin 1993).
Alcohol balance
When athletes ingest alcohol, it becomes a priority fuel, with a rapid rise in alcohol oxidation
occurring until all the alcohol is cleared from the
body. Alcohol also suppresses the oxidation of fat
and, to a lesser degree, that of protein and carbohydrate (Shelmet et al. 1988). Alcohol is not
stored as fat nor can it contribute to the formation
of muscle or liver glycogen. It may, however,
indirectly divert fat to storage by providing an
alternative and preferred energy source for
the body (Sonko et al. 1994). Thus, alcohol, at
29.4 kJ · g–1 (7 kcal · g–1), can contribute significantly to total energy intake. Athletes who
consume alcohol must reduce their intake of
energy from other sources to maintain energy
balance.
Energy balance
Determination of energy balance requires the
measurement or estimation of both energy intake
and energy expenditure. Energy balance is then
estimated by subtracting energy expenditure
from energy intake. This section will briefly
review the various components of energy intake
and expenditure, how these components are
measured, and the many factors that may influence them.
Components of energy expenditure
The components of total daily energy expenditure (TDEE) are generally divided into three
main categories: (i) resting metabolic rate (RMR),
(ii) the thermic effect of food (TEF), and (iii) the
thermic effect of activity (TEA) (Fig. 35.3). RMR is
the energy required to maintain the systems of
the body and to regulate body temperature at
rest. In most sedentary healthy adults, RMR
accounts for approximately 60–80% of TDEE
(Bogardus et al. 1986; Ravussin et al. 1986).
However, in an active individual this percentage
can vary greatly. It is not unusual for some
athletes to expend 4.2–8.4 MJ (1000–2000 kcal)
per day in sport-related activities. For example,
Thompson et al. (1993) determined energy
balance in 24 elite male endurance athletes over a
3–7-day period and found that RMR represented
only 38–47% of TDEE. Similar results are
reported in female runners (Beidleman et al.
1995).
The TEF is the increase in energy expenditure
above RMR that results from the consumption of
food throughout the day. It includes the energy
cost of food digestion, absorption, transport,
metabolism and storage within the body, and
the energy expended due to sympathetic
nervous system activity brought about by seeing,
smelling and eating food. TEF is usually
expressed as a percentage of the energy content
of the foods consumed and accounts for 6–10%
of TDEE, with women usually having a lower
value (approximately 6–7%) (Poehlman 1989).
However, this value will vary depending on the
energy density and size of the meal and types of
foods consumed. In addition, if the absolute
amount of energy intake is decreased, then it
follows that the absolute amount of energy
expended in TEF will decrease.
TEA is the most variable component of energy
expenditure in humans. It includes the energy
cost of daily activities above RMR and TEF, such
as purposeful activities of daily living (making
dinner, dressing, cleaning house) and planned
exercise (running, weight training, cycling). It
also includes the energy cost of involuntary muscular activity such as shivering and fidgeting.
This type of movement is called spontaneous
physical activity. TEA may be only 10–15% of
TDEE in sedentary individuals, but may be as
high as 50% in active individuals. The addition of
RMR, TEF and TEA should account for 100% of
the overweight athlete
100
Determinants
– Intensity
Unrestricted
activity
– Duration
Arousal
– Fat-free device
– Fat mass
– Age
25
SMR
BMR
– Sex
Respiratory chamber
– Amount/composition
of food (hormones/SNS)
Thermic effect
of food
Ventilated hood
% of daily energy expenditure
– Genetics/SNS?
SPA
Doubly labelled water
– Body weight
75
50
473
– Genetics
– Hormones/SNS
0
Methods
Fig. 35.3 Components of daily energy expenditure in humans. Daily energy expenditure can be divided into three
major components: (i) the basal metabolic rate (BMR) (the sum of the sleeping metabolic rate (SMR) and the energy
cost of arousal), which represents 50–70% of daily energy expenditure; (ii) the thermic effect of food, which
represents approximately 10% of daily energy expenditure; and (iii) the energy cost of physical activity (the sum of
spontaneous physical activity (SPA) and unrestricted/voluntary physical activity), which represents 20–40% of
daily energy expenditure. The major determinants of the different components of daily energy expenditure, as well
as the methods to measure them, are presented. SNS, sympathetic nervous system. From Ravussin and Swinburn
(1993).
TDEE. However, there are a variety of factors
that may increase energy expenditure above
normal, such as cold, fear, stress, and various
medications or drugs. These factors are referred
to as adaptive thermogenesis and represent a temporary increase in thermogenesis that may last
for hours or days, depending on the duration
and magnitude of the stimulus. For example, a
serious injury, the stress associated with competition, going to high altitudes, or the use of certain
drugs may all increase RMR.
Factors that influence RMR
It is well documented that RMR is influenced by
gender, age and body size, including the amount
of FFM and fat mass. These four variables generally explain about 80% of the variability in RMR
(Bogardus et al. 1986). Since FFM has a high
rate of metabolic activity, any change in FFM
would dramatically influence RMR. In general,
males have higher RMRs than females because
they usually weigh more and have more FFM.
However, Ferraro et al. (1992) found that females
have a lower RMR than males (approximately
100 kcal less per day) even after differences in
FFM, fat mass and age are controlled. Age is
another variable known to influence RMR. It is
estimated that the decline in RMR is less than
1–2% per decade from the second to the seventh
decade of life (Keys et al. 1983).
It is now known that RMR also has a genetic
component. This means that within a family
members may have similar RMRs. Two studies
illustrate this phenomenon. Bogardus et al. (1986)
found that family membership could explain
474
practical issues
11% of the variability in RMR (P < 0.0001) in
American Indians from 54 families. Similarly,
Bouchard et al. (1989) found that in twins and
parent–child pairs, heritability explained
approximately 40% of the variability in RMR
after adjusting for age, gender and FFM.
Research now indicates that RMR may fluctuate over the phases of the menstrual cycle, with
RMR values lowest during the follicular phase
and highest during the luteal phase (Solomon
et al. 1982; Bisdee et al. 1989). The difference in
RMR between these two phases is approximately
420–1260 kJ · day–1 (100–300 kcal · day–1). It also
appears that adaptations in energy intake mimic
the changes in RMR. Barr et al. (1995) found that
females consume approximately 1260 kJ · day–1
(300 kcal · day–1) more during the luteal phase of
the menstrual cycle than during the follicular
phase. Thus, the increased energy expenditure,
due to a higher RMR during the luteal phase, is
compensated by an increase in energy intake
during this period. However, if an athlete is
amenorrhoeic, these changes in RMR will not
occur. Data are not available for anovulatory
females who may be menstruating but have
depressed hormonal profiles. Although there
is substantial research to suggest that RMR
changes over the menstrual cycle, not all research
is supportive of these findings. Weststrate (1993)
showed no effect of menstrual cycle on RMR, and
Piers et al. (1995) showed no effect of menstrual
cycle phase on RMR or energy intake.
effect of exercise on rmr
For the athlete participating in an intense training programme, exercise may affect RMR both
directly and indirectly. First, exercise can directly
increase RMR if it increases FFM (Bogardus et al.
1986). Second, intense exercise training can
temporarily increase resting energy expenditure
above the typical RMR long after the exercise
bout has ended. This short-term increase in
energy expenditure is termed excess postexercise
oxygen consumption (EPOC) and is the amount
of energy expended above the typical RMR. The
extent of EPOC after an exercise bout and the
effect it has on TDEE appears to depend on
the exercise intensity and/or the duration (Bahr
1992). For example, Bahr et al. (1987) found that
.
aerobic exercise (70% Vo2max.) lasting 80 min produced a 15% increase in EPOC lasting for 12 h
after exercise. Similarly, 2 min of exercise at 108%
.
Vo2max., repeated three times, produced a significant increase in EPOC for 4 h after exercise (Bahr
et al. 1992). Although most research has examined the effect of aerobic exercise on EPOC,
Melby et al. (1993) found a significant increase in
EPOC after 90 min of weightlifting. Oxygen consumption was elevated by 5–10% over baseline
the following morning.
Finally, it appears that energy flux can also
alter RMR. Energy flux is defined as the amount
of energy expended in exercise compared with
the amount of energy consumed each day. An
athlete who is exercising intensely and eating
adequate energy would be in high energy flux,
while an athlete who is exercising intensely, but
restricting energy intake would be in negative
energy flux. Bullough et al. (1995) examined the
effect of energy flux on RMR in trained male
athletes. They measured RMR after 3 days of
high-intensity exercise (90 min of cycling at 75%
.
Vo2max., while eating adequate energy) and after
3 days of exercise when energy intake was
reduced (energy intake matching that required
on a no-exercise day). They found that RMR
was significantly higher during high energy than
during negative energy flux. Thus, two athletes
may be doing similar workouts, but have dramatically different energy expenditures if one is
restricting energy intake and the other is not.
Factors that influence TEF
A number of factors can influence how athletes’
bodies respond metabolically to the food they
consume. Some of these factors are associated
with the physiological characteristics of an individual such as genetic background, age, level of
physical fitness, sensitivity to insulin, or level of
body fat. Other factors are associated with the
meal, such as meal size, composition, palatability
and timing.
the overweight athlete
effect of food composition,
meal size and exercise
The TEF can last for several hours after a meal
and will depend on the amount of energy consumed and the composition of the meal. In
general, the thermic effect of a mixed meal is estimated to be 6–10% of total daily energy intake;
however, the total TEF will also depend on
the macronutrient composition of the diet. For
example, the thermogenic effect of glucose is
5–10%, fat is 3–5% and protein is 20–30% (Flatt
1992). Carbohydrate and fat have a lower
thermic effect than protein because less energy is
required to process, transport and convert carbohydrate and fat into their respective storage
forms. Conversely, protein synthesis and metabolism are more energy demanding. Thus, diets
higher in fat will have a lower TEF than diets that
contain more carbohydrate or protein. In addition, a diet high in energy will have a higher TEF
than a diet lower in energy because there is more
food to be digested, transported and stored. For
example, the TEF of an individual who consumes
12.6 MJ (3000 kcal) daily would be approximately
756–1260 kJ · day–1 (180–300 kcal · day–1), while an
individual consuming only 6.3 MJ (1500 kcal)
daily would have a TEF of 378–630 kJ · day–1
(90–150 kcal · day–1). The total TEF for a day does
not appear to be influenced by meal size or
number, as long as the same amount of energy is
consumed throughout the day (Belko & Barbieri
1987). Thus, the TEF will depend both on the
amount of energy consumed each day and the
composition of this energy.
Although exercise may influence the TEF,
there are few data available on the effect of exercise before and after a meal in trained athletes.
One study in trained swimmers reported that 45
min of swimming significantly increased the
metabolic response to a meal when the meal
preceded the exercise (104.2 kJ · h–1, 24.8 kcal · h–1)
compared with no exercise (84.8 kJ · h–1, 20.2 kcal ·
h–1) (Nichols et al. 1988). However, this difference
is so small that its long-term significance on
energy regulation is negligible, especially considering the high variability in the termic effect of
475
a meal (TEM) measurement between individuals. Similar results are reported by Bahr (1992),
who exercised physically active males for 80 min
.
at 75% Vo2max. and measured oxygen consumption after exercise. In the treatment condition
subjects were fed a meal 2 h after exercise, while
subjects fasted in the control condition. They
found only a 42-kJ (10-kcal) difference between
the two conditions over a 5-h postexercise
period.
Measurement of energy expenditure
Energy expenditure can be measured in the laboratory or estimated using prediction equations.
Since access to a laboratory for the measurement
of energy expenditure (calorimetry or doubly
labelled water) may be limited, this review will
focus on the prediction methods used to estimate
energy expenditure.
pr edic ting ener g y expenditur e
One of the most commonly used methods for
estimating TDEE is to predict RMR using a prediction equation and then multiply RMR by an
appropriate activity factor (Food and Nutrition
Board 1989; Montoye et al. 1996). A number of
prediction equations have been developed to
estimate RMR, but most have been developed
using sedentary populations. To date, no equation has been developed to predict the RMR of
athletes who may spend hours in training each
week. Some of the commonly used RMR prediction equations and the population from which
these equations were derived are discussed
below. To determine which of these equations
work best for athletes, Thompson and Manore
(1996) compared the measured RMR values from
indirect calorimetry with predicted RMR values
using the following equations. In all these equations, weight (wt) was measured in kilograms,
height (ht) in centimetres and age in years; LBM
stands for lean body mass.
• Harris and Benedict (1919); based on 239
subjects, 136 men (mean age, 27 ± 9 years; mean
weight, 64 ± 10 kg) and 103 women (mean age,
476
practical issues
33 ± 14 years; mean weight, 56.5 ± 11.5 kg), including trained male athletes. Harris and Benedict
derived different equations for both men and
women:
Males: RMR = 66.47 + 13.75 (wt) – 5 (ht)
– 6.76 (age)
Females: RMR = 655.1 9.56 (wt) + 1.85 (ht)
– 4.68 (age)
• Owen et al. (1986); based on 44 lean and obese
women, eight of whom were trained athletes
(age range, 18–65 years; weight range, 48–
143 kg), none of whom were menstruating
during the study, and all of whom were weight
stable for at least 1 month:
Active females: RMR = 50.4 + 21.1 (wt)
Inactive females: RMR = 795 + 7.18 (wt)
• Owen et al. (1987); based on 60 lean and obese
men (age range, 18–82 years; weight range,
60–171 kg), none of whom were athletes, and all
of whom were weight stable for at least 1 month:
Males: RMR = 290 + 22.3 (LBM)
Males: RMR = 879 + 10.2 (wt)
• Mifflin et al. (1990); based on 498 healthy lean
and obese subjects, 247 females and 251 males
(age range, 18–78 years; weight range, 46–120 kg
for women and 58–143 kg for men); no mention
was made of physical activity level:
RMR = 9.99 (wt) + 6.25 (ht) – 4.92 (age)
+ 166 (sex; male = 1, female = 0) – 161
• Cunningham (1980); based on 223 subjects, 120
males and 103 females, from the Harris and
Benedict data base. Cunningham eliminated 16
males who were identified as trained athletes. In
this study, LBM accounted for 70% of the variability of RMR. LBM was not calculated in the
Harris–Benedict equation, so Cunningham estimated LBM based on body mass and age:
RMR = 500 + 22 (LBM)
Thompson and Manore (1996) found that for
both male and female athletes the Cunning-
ham equation best predicted RMR, with the
Harris–Benedict equation being the next best
predictor. Because the Cunningham equation requires the measurement of FFM, the
Harris–Benedict equation will be easier to use in
settings where FFM cannot be measured.
Once RMR has been estimated, TDEE can then
be estimated by a variety of different factorial
methods. These methods vary in how labour
intensive they are to use and the level of respondent burden. A detailed description of these
methods is given elsewhere (Food and Nutrition
Board 1989; Schutz & Jequier 1994; Montoye et al.
1996). The easiest method multiplies RMR by an
appropriate activity factor, with the resulting
value representing TDEE (Food and Nutrition
Board 1989). Another method estimates a general
activity factor (GAF) and a specific activity factor
(SAF). The GAF represents the energy expended
in doing everyday activities such as walking,
standing, driving, and watching television. The
SAF is the amount of activity expended in
specific exercises (e.g. running, swimming or
weight training) for a designated intensity and
amount of time. The SAF is calculated by multiplying the amount of time spent in an activity by
its energy requirement (Berning & Steen 1991;
Montoye et al. 1996). The GAF and SAF are
then added together to get the total amount of
energy expended per day in activity. This value is
added to the estimated RMR value, then an additional 6–10% is added to represent the TEF. The
final number then represents the TDEE. This
method is relatively easy to use with athletes
who have specific training or exercise programmes and who already keep training logs.
TDEE can also be estimated by recording all
activities over a 24-h period and then calculating
the energy expended in each of these activities
(kJ · kg–1 · min–1). The amount of energy expended
in each activity is then added and represents
TDEE. Many computer programs calculate
energy expenditure in this way. Regardless of the
method used, keep in mind that all values are
estimates. The accuracy of these values will
depend on a number of factors: the accuracy of
the activity records, the accuracy of the data base
the overweight athlete
used, and the accuracy with which the calculations are done.
Energy intake
Since energy intake is one part of the energy
balance equation, knowing total energy intake
will give some indication of TDEE if body weight
is stable. The assessment of dietary records is one
of the most frequently used procedures for monitoring the energy and nutrient intakes of athletes.
The goal of assessing dietary intake is to achieve
the most accurate description of the athlete’s
typical food intake. This information is then used
to assess mean energy intake and composition of
the diet, make recommendations for improving
food habits and adjusting energy intake, and
determine the need for micronutrient supplements while dieting.
methods for collecting energy
and nutrient intake data
For the athlete with limited time and skills for
recording food intake, retrospective methods,
such as 24-h diet recalls, food frequency questionnaires or diet histories, can be used. If
more specific energy or nutrient intake data are
needed, food records or weighed food records
should be used. Deciding which method to use
will depend on the capabilities and dedication
of the athlete, and the detail and specificity of
the data required by the sports medicine team
(Dwyer 1999).
The diet record is probably the most frequently
used method for assessing the energy and nutrient intake of athletes. A diet record is a list of all
food consumed over a specified time, such as 3–7
days. To more accurately predict energy and
nutrient intakes, it is best if foods consumed can
be weighed or measured, labels of convenience
foods saved, and all supplements recorded from
the label. This method also allows for the gathering of more in-depth information such as the
time, place, feelings, and behaviours associated
with eating. The dietitian working with the
athlete can review the diet record to ensure its
477
accuracy. A primary drawback of this method is
the tendency for individuals to change their
‘typical eating habits’ on days they record food
intake. This method is also more time consuming
than a 24-h recall; thus, the accuracy of the diet
record depends on the individual’s cooperation
and skill in recording foods properly.
How many days must be recorded to give an
accurate picture of an athlete’s diet? Diet records
lasting from 3 to 14 days will provide good estimates of energy and nutrient intakes (Schlundt
1988). Within this range, reliability and accuracy
appear to increase with each additional day up to
7 days. Thus, a 7-day diet record can give accurate data for energy and most nutrients. One
advantage of the 7-day diet record is that it
encompasses all the days of the week, including
the dietary changes that frequently occur on
weekends and the athlete’s weekly training
routine. The disadvantage of this method is that
as the number of days increases, so does the
respondent burden. If only 3–4-day diet records
are used, care should be taken in choosing which
days will be recorded.
Practical guidelines for achieving a
competitive body weight
For the overweight athlete, any weight loss
attempt should be aimed at achieving a competitive body weight and composition that is optimal
for performance and health. What is an optimal
body weight for performance? How is this
number determined? Who determines this goal?
These are difficult questions that need to be
addressed by the athlete in consultation with the
sports medicine team before a weight loss programme can begin. If the athlete is young and
still growing, these questions are even harder.
Table 35.1 gives ranges of relative body fat levels
for elite athletes in various sports; Berning and
.
Steen (1998) also give body fat and Vo2max. data
for athletes of varying ages. These ranges,
however, do not take into account individual
variability regarding body fat and performance.
In addition, some athletes will perform at their
best outside of these ranges. Remember that a
478
practical issues
certain amount of body fat is essential for good
health. Finally, the inherent error of body composition assessment, 1–3% under ideal conditions,
must be considered (Wilmore 1992a).
Weight loss goals
The following outline offers some criteria and
questions that may be helpful in determining an
athlete’s optimal body weight.
1 Put emphasis on personal health and well
being, and fitness and performance goals — not
only weight.
• Set realistic weight goals. (What is your
current weight goal? Is body weight reduction
necessary? Is there any indication that weight
loss will improve performance? Have you ever
maintained your goal weight without dieting?
When was the last time you were at your goal
weight? At what weight or body-fat level do
you perform well, do you feel good and are
you injury free? What was the last weight you
could maintain without constantly dieting?)
• Place less focus on the scale and more on
changes in body composition and lifestyle,
such as stress management and making good
food choices.
• Pick the appropriate weight loss technique
that works with your training schedule.
Weight loss should be gradual, at approximately 0.5–1.0 kg · week-1.
• Mark progress by measuring changes in
fitness level and performance levels (personal
record times, level of fatigue at the end of a
workout, level of energy at the end of the day,
strength and power changes), and general
overall well-being.
2 Make changes in diet and eating behaviour.
• Do not starve yourself or restrict energy too
severely. Do not go below 5–6.4 MJ (1200–
1500 kcal) daily for women and 6.4–7.6 MJ
(1500–1800 kcal) daily for men.
• Do not constantly deprive yourself of
favourite foods or set unrealistic dietary rules.
• Make basic dietary changes that moderately
reduce energy intake, that fit into your
lifestyle, and that you know you can achieve.
• Reduce fat intake but remember, a lower fat
diet will not guarantee weight loss if a negative energy balance is not achieved.
• Eat more whole grains, cereals, fruits, and
vegetables, and get adequate fibre (> 25 g ·
day-1).
• Do not skip meals and do not let yourself get
too hungry. Eat something for breakfast. This
will prevent you from being too hungry and
overeating later in the day.
• Reduce or eliminate late night eating.
• Plan ahead and be prepared for when you
might get hungry. Carry healthy snacks with
you. Always eat high carbohydrate foods immediately after strenuous exercise.
• Identify your dietary weaknesses; plan a
strategy for dealing with these difficult times.
Are you eating when you are bored,
depressed, upset? Do you overeat when you
are around food or eat out?
• Do not go into a training session or competition without eating adequately. Be sure you are
well fed both before and after you exercise.
3 Make changes in exercise behaviour.
• If you do not already do aerobic exercise and
strength training, start and maintain an exercise programme that includes both of these
components. This is an absolute requirement
for burning fat and the maintenance of a
healthy competitive body weight. Strength
training will help maintain FFM while you are
working to lose body fat.
• Plan regular exercise into your day (outside
your training sessions) and add additional
exercise by walking instead of driving, or
using the stairs instead of the elevator.
(Adapted from Burke 1995; Manore 1996.)
Optimal body weight should be a weight that
promotes both good health and performance,
and is ‘reasonable’ to achieve and maintain. If an
athlete has never been able to achieve or maintain his or her goal weight, then this may be an
unrealistic weight that places them under unnecessary psychological stress. Determination of an
athlete’s optimal weight must also consider the
genetic background, age, gender, sport, health
and past weight history. For the female athlete,
the overweight athlete
knowing menstrual history will also be important in setting weight loss and dietary goals
(Dueck et al. 1996).
Body composition should be measured and
weight loss goals centred on the loss of body fat
instead of just weight. This way the goal is
shifted to changes in body composition instead
of weight (Table 35.1). Knowing body composition also helps prevent the athlete from losing too
much weight or setting an unachievable goal.
This information can then be used to determine
an optimal body weight and to set fat loss goals.
For the athlete who is already lean, yet wants to
diet, this process can help convince him or her
Table 35.1 Ranges of relative body fat for men and
women athletes in various sports. From Wilmore
(1992b), with permission.
Sport
Men
Women
Baseball, softball
Basketball
Body building
Canoeing and kayaking
Cycling
Fencing
Football
Golf
Gymnastics
Horse racing
Ice and field hockey
Orienteering
Pentathlon
Racketball
Rowing
Rugby
Skating
Ski jumping
Skiing
Soccer
Swimming
Synchronized swimming
Tennis
Track and field
Field events
Running events
Triathlon
Volleyball
Weightlifting
Wrestling
8–14
6–12
5–8
6–12
5–11
8–12
6–18
10–16
5–12
6–12
8–16
5–12
—
6–14
6–14
6–16
5–12
7–15
7–15
6–14
6–12
—
6–14
12–18
10–16
6–12
10–16
8–15
10–16
—
12–20
8–16
10–16
12–18
8–16
8–15
10–18
8–16
—
8–16
10–18
10–18
10–18
10–18
10–18
10–20
8–18
5–12
5–12
7–15
5–12
5–16
12–20
8–15
8–15
10–18
10–18
—
479
that weight loss is not necessary. Weight loss in a
lean athlete is not possible without seriously
compromising performance because of the
inevitable loss of FFM. These athletes will benefit
more from establishing good dietary practices
than from weight loss. These guidelines can also
be used with the young athlete who does not
want to gain weight even though growth and
weight gain should be occurring.
Role of diet
If the athlete does need to lose weight (body fat),
a weight loss plan needs to be developed early
in the athlete’s training programme to avoid
potentially harmful dieting practices and weight
cycling. Weight loss is not recommended during
periods of intense endurance training; athletes
cannot be expected to train intensely and
improve performance on low energy intakes.
Thus, weight loss goals should be set at approximately 0.5–1 kg · week–1, depending on body size
and gender, and focus on decreases in body fat,
while maintaining or increasing FFM (Wilmore
1992b; Fogelholm 1994). The degree of energy
restriction will depend on body size, typical
energy intake and expenditure, and the period
allotted for weight loss. In general, reducing
energy intake by 10–25% (approximately
1680–3360 kJ or 400–800 kcal daily) may be all
that is necessary. If the weight loss is occurring in
the off season, then both the restriction of energy
intake and increased energy expenditure need to
occur.
Severe energy restriction or fasting should not
be used with athletes. This approach to weight
loss only decreases carbohydrate and protein
intake and, thus, the ability to replace muscle
glycogen (Bogardus et al. 1981) and repair and
build muscle tissue after exercise. These types of
diets also increase the risk of injury and the feelings of fatigue after routine workouts, which in
turn can dramatically undermine self-confidence
and performance. Finally, these diets increase
FFM losses and decrease RMR (Donnelly et al.
1994; Thompson et al. 1996). These factors,
combined with the feelings of deprivation that
480
practical issues
accompany severe dieting, usually result in diet
failure or relapse.
If energy intake decreases below 7.6–8 MJ ·
day–1 (1800–1900 kcal · day–1), nutrient intakes
can be severely compromised (Beals & Manore
1994, 1998; Manore 1996). This level of energy
intake is not adequate to replace muscle glycogen and fuel the athlete during intense training
periods. Athletes have higher protein and carbohydrate requirements than their sedentary
counterparts (Coyle 1995; Lemon 1995). When
dieting, carbohydrate intake should remain as
high as possible (60–70% of energy) and protein
intake at 1.2–1.8 g · kg–1 body weight (Lemon
1995), while fat intake is reduced to 15–25% of
energy. Prolonged energy restriction also places
that athlete at risk for low dietary intakes of
calcium, iron, magnesium, zinc and B complex
vitamins (Manore 1996; Beals & Manore, 1998).
Thus, it may be necessary for athletes to use
vitamin and mineral supplements during long
periods of energy restriction (> 3–4 weeks). This
may be especially true if the athlete makes poor
food choices, eats primarily processed or convenience foods, or eliminates various food groups
from the diet.
Any weight loss plan for an athlete should
moderately reduce energy intake while teaching
good food choices. It is much easier to teach athletes how to eliminate or reduce high fat and
energy dense foods from their diet than to count
kilocalories. They also need to become aware of
the situations and emotions that trigger overeating or binge eating. Athletes need to learn the
nutrient composition of the foods they eat and
why they eat them. This knowledge is useful in
developing a diet plan around better food
choices, training schedules, budgets and periods
when overeating is most likely to occur.
Role of exercise
Exercise is necessary for both weight loss and
weight maintenance. Unlike the general population, most athletes participate in hard physical
activity. However, which activities are best for fat
loss? It is well documented that aerobic activity
oxidizes fat; however, recent evidence indicates
that high-intensity anaerobic activity added to
an aerobic exercise programme may be better at
reducing body fat than aerobic-only exercise
(Trembly et al. 1994). Weight training can also
help preserve FFM and strength while dieting
if energy restriction is not too severe (Donnelly
et al. 1994). Thus, the type of exercise added to
a weight-loss programme will depend on the
current training practices of the athlete.
Behaviour modification and
weight maintenance
In order for weight loss to be maintained,
changes in diet and exercise habits need to
become part of the athlete’s lifestyle. Foreyt and
Goodrick (1993) and Klem et al. (1996) found that
individuals who are successful at losing and
maintaining weight loss have the following
characteristics in common: they modify diet,
especially energy intake from fat; they exercise
regularly and monitor their weight; and they
have high levels of social support from family
and friends. These changes can be achieved by
first identifying the eating or exercise behaviour
that needs to be changed, then setting specific
and realistic goals for changing this behaviour.
Changes in behaviour should be made slowly
and modified as necessary. Finally, successful
behaviour is rewarded. This approach to weight
loss and maintenance will take time and may
require continuous social and professional
support (Foreyt & Goodrick 1991).
Conclusion
Successfully guiding the overweight athlete
through the weight loss process is a challenge for
both the athlete and the sports medicine team.
Identifying the appropriate weight loss goal and
method is imperative for a successful outcome.
These basic considerations need to be remembered before beginning any weight loss
programme:
• Both energy intake and expenditure are important. If energy intake is less than energy expendi-
the overweight athlete
ture, weight will be lost. Increases in energy
expenditure and moderate decreases in energy
intake may help preserve FFM and muscle
strength while dieting.
• Rate of weight loss is important. Do not use
severe energy restriction or fasting as a means of
weight loss. For most athletes, a weight loss of
0.5–1 kg · week–1 is the maximum recommended.
• Composition of the diet is important, especially for weight maintenance. Carbohydrate,
protein and alcohol oxidation appear to match
their energy intake, while fat oxidation does not.
• The protein/energy intake ratio is important. When energy intake is low, a higher
protein/energy ratio is required. In addition,
athletes have higher protein requirement than
sedentary individuals.
• Micronutrients are important. If dieting is
longer than 3–4 weeks, micronutrient supplementation may be required to meet the recommended intakes.
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