Position of the american dietetic association, dietitians of canada, and the american college of sports medicine: nutrition and athletic performance

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J Am Diet Assoc. 2009;109:509-527.
ity, athletic performance, and recovery
from exercise are enhanced by optimal
nutrition. These organizations recom-
mend appropriate selection of food
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tions specific to nutritional ergo- and fluids, timing of intake, and sup-oi: 10.1016/j.jada.2009.01.005
009 by the American Dietetic Association Journal of the AMERICAN DIETETIC ASSOCIATION 509
ough exercise performance can be
ected by body weight and compo-
ion, these physical measures
ould not be a criterion for sports
rformance and daily weigh-ins
e discouraged. Adequate food and
id should be consumed before,
and hyponatremia. Vitamin and
mineral supplements are not needed
if adequate energy to maintain body
weight is consumed from a variety
of foods. However, athletes who re-
strict energy intake, use severe
weight-loss practices, eliminate one
POSITION STATEMENT
It is the position of the American Die-
tetic Association, Dietitians of Can-
ada, and the American College of
Sports Medicine that physical activ-
from th
Position o
Dietitians of Ca
Sports Medicine
STRACT
is the position of the American Die-
ic Association, Dietitians of Canada,
d the American College of Sports
dicine that physical activity, ath-
ic performance, and recovery from
ercise are enhanced by optimal
trition. These organizations rec-
mend appropriate selection of
ds and fluids, timing of intake,
d supplement choices for optimal
alth and exercise performance.
is updated position paper couples
rigorous, systematic, evidence-
sed analysis of nutrition and
rformance-specific literature with
rrent scientific data related to
ergy needs, assessment of body
position, strategies for weight
ange, nutrient and fluid needs,
ecial nutrient needs during train-
and competition, the use of
pplements and ergogenic aids, nu-
tion recommendations for vege-
ian athletes, and the roles and
ponsibilities of sports dietitians.
ergy and macronutrient needs,
ecially carbohydrate and protein,
st be met during times of high
ysical activity to maintain body
ight, replenish glycogen stores,
d provide adequate protein to
ild and repair tissue. Fat intake
ould be sufficient to provide the
ential fatty acids and fat-soluble
e assoc
the American Die
ada, and the Am
Nutrition and Ath
intain blood glucose concentra-
n during exercise, maximize exer-
e performance, and improve re-
ery time. Athletes should be well
drated before exercise and drink
ough fluid during and after exer-
e to balance fluid losses. Sports
verages containing carbohydrates
d electrolytes may be consumed
fore, during, and after exercise to
lp maintain blood glucose concen-
This American Dietetic Association
vidence Analysis Process and inform
ibrary. Similar information is also av
ractice-based Evidence in Nutrition
roach provides important added ben
ajor advantage of the approach is th
eview criteria, which minimizes the
reases the ease with which disparat
etailed description of the methods us
ccess ADA’s Evidence Analysis Proce
Conclusion Statements are assigned
ased on the systematic analysis and e
vidence. Grade I�Good, Grade II�F
xpert Opinion Only, and Grade V�Gr
no evidence to support or refute the
Evidence-based information for this
ww.adaevidencelibrary.com and ww
criptions for non-ADA members are
ww.adaevidencelibrary.com/store.cfm
anada and non-Dietitians of Canada
ased Evidence in Nutrition at http://w
sp.
iation
etic Association,
rican College of
tic Performance
nic aids are poorly enforced, they
ould be used with caution, and
ly after careful product evalua-
n for safety, efficacy, potency, and
ality. A qualified sports dietitian
d in particular in the United
ates, a Board Certified Specialist
Sports Dietetics, should provide
ividualized nutrition direction
d advice subsequent to a compre-
nsive nutrition assessment.
DA) position paper uses ADA’s
on from ADA’s Evidence Analysis
lable from Dietitians of Canada’s
he use of an evidence-based ap-
s to earlier review methods. The
more rigorous standardization of
elihood of reviewer bias and in-
rticles may be compared. For a
in the evidence analysis process,
at http://adaeal.com/eaprocess/.
grade by an expert work group
uation of the supporting research
, Grade III�Limited, Grade IV�
Is Not Assignable (because there
nclusion).
nd other topics can be found at
ieteticsatwork.com/pen and sub-
vailable for purchase at https://
Subscriptions for Dietitians of
mbers are available for Practice-
w.dieteticsatwork.com/pen_order.
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510
ment choices for optimal health
d exercise performance.
he following key points summa-
rize the current energy, nutrient,
and fluid recommendations for
ive adults and competitive ath-
es. These general recommenda-
ns can be adjusted by sports nutri-
n experts to accommodate the
ique concerns of individual ath-
es regarding health, sports, nutri-
t needs, food preferences, and body
ight and body composition goals.
thletes need to consume adequate
nergy during periods of high-in-
ensity and/or long-duration train-
ng to maintain body weight and
ealth and maximize training ef-
ects. Low energy intakes can result
n loss of muscle mass; menstrual
ysfunction; loss of or failure to
ain bone density; an increased risk
f fatigue, injury, and illness; and a
rolonged recovery process.
ody weight and composition should
ot be the sole criterion for participa-
ion in sports; daily weigh-ins are dis-
ouraged. Optimal body fat levels de-
end upon the sex, age, and heredity
f the athlete, and may be sport-spe-
ific. Body fat assessment techniques
ave inherent variability and limita-
ions. Preferably, weight loss (fat
oss) should take place during the off-
eason or begin before the competi-
ive season and involve a qualified
ports dietitian.
arbohydrate recommendations for
thletes range from 6 to 10 g/kg (2.7
o 4.5 g/lb) body weight per day.
arbohydrates maintain blood glu-
ose levels during exercise and re-
lace muscle glycogen. The amount
equired depends upon the athlete’s
otal daily energy expenditure, type
f sport, sex, and environmental
onditions.
rotein recommendations for endur-
nce and strength-trained athletes
ange from 1.2 to 1.7 g/kg (0.5 to 0.8
/lb) body weight per day. These rec-
mmended protein intakes can gen-
rally be met through diet alone,
ithout the use of protein or amino
cid supplements. Energy intake suf-
cient to maintain body weight isecessary for optimal protein use
nd performance.
at intake should range from 20%
o 35% of total energy intake. Con-
uming �20% of energy from fat �
March 2009 Volume 109 Number 3
oes not benefit performance. Fat,
hich is a source of energy, fat-sol-
ble vitamins, and essential fatty
cids, is important in the diets of
thletes. High-fat diets are not rec-
mmended for athletes.
thletes who restrict energy intake
r use severe weight-loss practices,
liminate one or more food groups
rom their diet, or consume high- or
ow-carbohydrate diets of low mi-
ronutrient density are at greatest
isk of micronutrient deficiencies.
thletes should consume diets that
rovide at least the Recommended
ietary Allowance (RDA) for all mi-
ronutrients.
ehydration (water deficit in excess
f 2% to 3% body mass) decreases
xercise performance; thus, ade-
uate fluid intake before, during,
nd after exercise is important for
ealth and optimal performance.
he goal of drinking is to prevent
ehydration from occurring during
xercise and individuals should not
rink in excess of sweating rate. Af-
er exercise, the athlete should
rink adequate fluids to replace
weat losses during exercise, ap-
roximately 16 to 24 oz (450 to 675
L) fluid for every pound (0.5 kg) of
ody weight lost during exercise.
efore exercise, a meal or snack
hould provide sufficient fluid to
aintain hydration, be relatively
ow in fat and fiber to facilitate gas-
ric emptying and minimize gastro-
ntestinal distress, be relatively
igh in carbohydrate to maximize
aintenance of blood glucose, be
oderate in protein, be composed of
amiliar foods, and be well tolerated
y the athlete.
uring exercise, primary goals for
utrient consumption are to replace
uid losses and provide carbohy-
rates (approximately 30 to 60 g per
our) for maintenance of blood glu-
ose levels. These nutrition guide-
ines are especially important for en-
urance events lasting longer than
n hour when an athlete has not con-
umed adequate food or fluid before
xercise, or if an athlete is exercising
n an extreme environment (eg, heat,
old, or high altitude).
fter exercise, dietary goals are to
rovide adequate fluids, electrolytes,
nergy, and carbohydrates to replace
uscle glycogen and ensure rapid re-
overy. A carbohydrate intake of
1.0 to 1.5 g/kg (0.5 to 0.7 g/lb) body gra
eight during the first 30 minutes
nd again every 2 hours for 4 to 6
ours will be adequate to replace gly-
ogen stores. Protein consumed after
xercise will provide amino acids for
uilding and repair of muscle tissue.
n general, no vitamin and mineral
upplements are required if an ath-
ete is consuming adequate energy
rom a variety of foods to maintain
ody weight. Supplementation rec-
mmendations unrelated to exercise,
uch as folic acid for women of child-
earing potential, should be followed.
multivitamin/mineral supplement
ay be appropriate if an athlete is
ieting, habitually eliminating foods
r food groups, is ill or recovering
rom injury, or has a specific micro-
utrient deficiency. Single-nutrient
upplements may be appropriate for
specific medical or nutritional rea-
on (eg, iron supplements to correct
ron deficiency anemia).
thletes should be counseled re-
arding the appropriate use of ergo-
enic aids. Such products should
nly be used after careful evalua-
ion for safety, efficacy, potency,
nd legality.
egetarian athletes may be at risk
or low intakes of energy, protein,
at, and key micronutrients such as
ron, calcium, vitamin D, riboflavin,
inc, and vitamin B-12. Consulta-
ion with a sports dietitian is rec-
mmended to avoid these nutrition
roblems.
DENCE-BASED ANALYSIS
dies used in the development of
s position paper were identified
m the PubMed database main-
ned by the National Library of
dicine and CENTRAL database, as
ll as through research articles and
rature reviews. Five topic-specific
estions were identified for evi-
nce-based analysis (Figure 1) and
orporated into this position, updat-
the prior position on nutrition and
rformance (1). Search terms used
re athlete, performance, power,
ength, endurance, or competition
d macronutrient, meal, carbohy-
te, fat, protein, or energy. For the
rpose of this analysis, inclusion cri-
ia were adults aged 18 to 40 years;
sport settings; and trained ath-
es, athletes in training, or individ-
ls regularly exercising. Since the
ding system used provides allow-
an
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Fig tion
the nad
pos
ces for consideration of study de-
n, the evidence-based analysis was
t limited to randomized controlled
als. Study design preferences were
domized controlled trials or clini-
controlled studies; large nonran-
mized observational studies; and
ort, case-control studies. All sam-
sizes were included and study
p out rate could not exceed 20%.
e publication range for the evi-
nce-based analysis spanned 1995-
06. If an author was included on
re than one review article or pri-
ry research article which were
ilar in content, the most recent
per was accepted and earlier ver-
ns rejected. However, when an au-
r was included on more than one
iew article or primary research ar-
le for which content differed, then
th reviews could be accepted for
alysis.
he following exclusion criteria
re applied to all identified studies:
dults older than age 40 years,
oung adults younger than age 18
ears, infants, children, and adoles-
ents;
ettings not related to sports;
onathletes;
ritical illness and other diseases
nd conditions;
rop out rates �20%;
ublication before 1995;
tudies by same author that were
imilar in content; and
opic Question
Energy balance and
body composition
What is the rela
body compos
athletic perfo
Training What is the evid
energy intake
athletic perfo
Competition What is the evid
energy intake
athletic perfo
hours before
What is the evid
energy intake
athletic perfo
Recovery What is the evid
energy intake
athletic perfo
ure 1. Specific topics and the respective ques
American Dietetic Association, Dietitians of Ca
ition on nutrition and athletic performance.
rticles not in English. tha
onclusion statements were formu-
ed summarizing the strength of evi-
ce with respect to each question
gure 1). The strength of the evidence
s graded using the following ele-
nts: quality, consistency across
dies, quantity, and generalizability.
more detailed description of the
thodology used for this evidence-
sed analysis may be found on the
erican Dietetic AssociationWeb site
www.eatright.org/cps/rde/xchg/ada/
xsl/8099_ENU_HTML.htm.
ERGY METABOLISM
ergy expenditure must equal en-
y intake to achieve energy bal-
ce. The energy systems used during
rcise for muscular work include
phosphagen and glycolytic (both
aerobic) and the oxidative (aerobic)
thways. The phosphagen system is
ed for events lasting no longer than
ew seconds and of high intensity.
enosine triphosphate (ATP) and cre-
ne phosphate provide the readily
ailable energy present within the
scle. The amount of ATP present in
letal muscles (�5 mmol/kg wet
ight) is not sufficient to provide a
tinuous supply of energy, especially
high exercise intensities. Creatine
osphate is an ATP reserve in muscle
t can be readily converted to sustain
ivity for �3 to 5 minutes (2). The
ount of creatine phosphateavailable
skeletal muscle is �4 times greater
ship between energy balance/imbalance,
, and/or weight management and
nce?
e to support a particular meal timing,
d macronutrient intake for optimal
nce during training?
e to support a particular meal timing,
d macronutrient intake for optimal
nce during competition during the 24
petition?
e to support a particular meal timing,
d macronutrient intake for optimal
nce during competition?
e to support a particular meal timing,
d macronutrient intake for optimal
nce during recovery?
s used for the evidence analysis sections of
a, and American College of Sports Medicine
n ATP, and therefore, is the pri- exe
March 2009 ● Journal o
ry fuel used for high intensity, short
ration activities such as the clean
d jerk in weight lifting, or fast break
basketball.
he anaerobic glycolytic pathway
es muscle glycogen and glucose
t are rapidly metabolized anaero-
ally through the glycolytic cascade.
is pathway supports events lasting
to 180 seconds. Approximately
% to 35% of total muscle glycogen
res are used during a single 30-
ond sprint or resistance exercise
ut. Neither the phosphagen nor the
colytic pathway can sustain the
id provision of energy to allow
scles to contract at a very high
e for events lasting greater than
to 3 minutes.
he oxidative pathway fuels events
ting longer than 2 to 3 minutes.
e major substrates include muscle
d liver glycogen, intramuscular,
od, and adipose tissue triglycer-
s, and negligible amounts of amino
ds from muscle, blood, liver, and
gut. Examples of events for which
major fuel pathway is the oxida-
e pathway include a 1,500-meter
n, marathon, half-marathon, and
durance cycling or �500 meter
imming events. As oxygen becomes
re available to the working muscle,
body uses more of the aerobic (ox-
tive) pathways and less of the an-
robic (phosphagen and glycolytic)
thways. Only the aerobic pathway
produce large amounts of ATP
er time via the Kreb’s cycle and
e electron transport system. The
ater dependence upon aerobic
thways does not occur abruptly,
r is one pathway ever relied on
clusively. The intensity, duration,
quency, type of activity, sex, and
ness level of the individual, as
ll as prior nutrient intake and en-
y stores, determine when the
ssover from primarily aerobic to
aerobic pathways occurs (2).
version of Energy Sources Over Time
proximately 50% to 60% of energy
ring 1 to 4 hours of continuous ex-
ise at 70% of maximal oxygen ca-
city is derived from carbohydrates
d the rest from free fatty acid oxi-
tion (3). A greater proportion of en-
y comes from oxidation of free
ty acids, primarily those from mus-
triglycerides as intensity of the
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512
t alter the total amount of energy
ended but rather the proportion of
ergy derived from carbohydrates
d fat (3). As a result of aerobic
ining, the energy derived from fat
reases and from carbohydrates de-
ases. A trained individual uses a
ater percentage of fat than an un-
ined person does at the same work-
d (2). Long-chain fatty aids derived
m stored muscle triglycerides are
preferred fuel for aerobic exercise
individuals involved in mild- to
derate-intensity exercise (4).
ERGY REQUIREMENTS
eting energy needs is a nutrition
ority for athletes. Optimum athletic
formance is promoted by adequate
ergy intake. This section provides in-
mation necessary to determine en-
y balance for an individual. Energy
lance occurs when energy intake (the
of energy from foods, fluids, and
plement products) equals energy
enditure or the sum of energy ex-
ded as basal metabolic rate; the
rmic effect of food; and the thermic
ect of activity, which is the energy
ended in planned physical activity
d nonexercise activity thermogenesis
. Spontaneous physical activity is
o included in the thermic effect of
ivity.
thletes need to consume enough
ergy to maintain appropriate
ight and body composition while
ining for a sport (6). Although
ual energy intakes for many in-
sely training female athletes
ght match those of male athletes
r kilogram body weight, some fe-
le athletes may consume less en-
y than they expend. Low energy
ake (eg, �1,800 to 2,000 kcal/day)
female athletes is a major nutri-
nal concern because a persistent
te of negative energy balance can
d to weight loss and disruption of
docrine function (7-10).
nadequate energy intake relative
energy expenditure compromises
rformance and negates the benefits
training. With limited energy in-
e, fat and lean tissue will be used
fuel by the body. Loss of lean tis-
e mass results in the loss of
ength and endurance, as well as
promised immune, endocrine,
d musculoskeletal function (11). In
dition, chronically low energy in-
e results in poor nutrient intake, est
March 2009 Volume 109 Number 3
rticularly of the micronutrients
d may result in metabolic dysfunc-
ns associated with nutrient defi-
ncies as well as lowered resting
tabolic rate. The newer concept of
ergy availability, defined as dietary
ake minus exercise energy expen-
ure normalized to fat-free mass
M), is the amount of energy avail-
le to the body to perform all other
ctions after exercise training ex-
nditure is subtracted. Many re-
rchers have suggested that 30
l/kg FFM/day might be the lower
eshold of energy availability for
men (12-15).
stimation of energy needs of ath-
es and active individuals can be
ne using a variety of methods. The
etary Guidelines for Americans
05 (16) and the Dietary Reference
akes (15,17) provide energy recom-
ndations for men and women who
slightly to very active that are
sed on predictive equations devel-
ed using the doubly labeled water
hnique, which can also be used to
imate energy needs of athletes
gure 2).
nergy expenditure for different
es of exercise is dependent upon
duration, frequency, and inten-
y of the exercise, the sex of the ath-
e, and prior nutritional status. He-
ity, age, body size, and FFM also
uence energy expenditure. The
re energy used in activity, the
re energy needed to achieve energy
lance.
ypical laboratory facilities are
ually not equipped to determine to-
energy expenditure. Therefore,
dictive equations are often used to
dult man
62�9.53 (age in years)�PAa [15.91 (weight
dult woman
54�6.91 (age in years)�PA [9.36 (weight in
A level
.0-1.39 Sedentary, typical daily living acti
.4-1.59 Low active, typical daily living ac
activity (eg, walking at 5-7 km/h)
.6-1.89 Active, typical daily living activitie
activity.
.9-2.5 Very active, typical daily activities
activity plus an additional 60 min
moderate activity.
ure 2. The Dietary Reference Intake (DRI) m
lts. Adapted from reference 17. aPA�physica
imate basal metabolic rate or rest- gre
metabolic rate. The two prediction
uations considered to most closely
imate energy expenditure are the
nningham equation (18) and the
rris-Benedict equation (19). Be-
se the Cunningham equation re-
ires that lean body mass be known,
rts dietitians typically use the
rris-Benedict equation.To esti-
te total energy expenditure, basal
tabolic rate or resting metabolic
e is then multiplied by the appro-
ate activity factor of 1.8 to 2.3 (rep-
enting moderate to very heavy
ysical activity levels, respectively).
meric guidelines such as these (8)
ly provide an approximation of the
erage energy needs of an individual
lete. An alternative method for es-
ating exercise energy expenditure
to use metabolic equivalents re-
ded over a 24-hour period (20). Any
these methods can be used to esti-
te energy expenditure for the de-
mination of energy intake require-
nts and provide a sports dietitian
th a basis to guide an athlete or
ive individual in meeting their en-
y needs.
DY COMPOSITION
dy composition and body weight
two of the many factors that con-
bute to optimal exercise perfor-
nce. Taken together, these two fac-
s may affect an athlete’s potential
success for a given sport. Body
ight can influence an athlete’s
ed, endurance, and power,
ereas body composition can affect
athlete’s strength, agility, and ap-
arance. A lean body (ie, one with
ilograms)�539.6 (height in meters)].
grams)�726 (height in meters)]
s (eg, household tasks, walking to bus).
ies plus 30-60 minutes of daily moderate
lus 60 minutes of daily moderate
s at least 60 minutes of daily moderate
of vigorous activity or 120 minutes of
od for estimating energy requirement for
tivity.
wi
act
erg
BO
Bo
are
tri
ma
tor
for
we
spe
wh
an
pe
ater muscle/fat ratio) is often ad-
va
inv
A
cu
bo
tha
sit
ath
an
for
wh
spo
we
los
spe
pa
su
sk
to
lea
we
ap
str
fat
ath
I
ath
we
tag
pe
the
tor
let
com
bo
wh
for
M
for
mu
No
the
ad
kn
wi
an
spe
an
of
ue
Ass
Th
niq
po
ba
tho
de
Th
ind
do
III
ter
sor
ple
niq
an
(B
II
in
U
ere
com
om
bon
bod
tho
etr
inv
ins
Air
(Bo
cor
bod
an
usi
lea
me
ses
un
chi
T
Le
su
me
wr
fol
by
com
sit
bic
sca
Th
tio
vid
an
(22
fol
fat
pro
an
by
po
ity
eq
sit
me
tor
cal
De
sk
rem
is
US
Ki
eff
me
Co
sev
Int
Ki
ing
du
ing
per
B
an
du
bo
su
ma
Wh
of
thr
on
fai
wa
de
cau
mu
fai
sta
tha
ag
of
me
cau
sk
su
low
be
eva
Bod
Per
Bo
de
an
lev
he
wo
fat
let
mi
on
tio
thr
ind
the
for
(26
sh
sel
tea
ven
ntageous in sports where speed is
olved.
thletic performance cannot be ac-
rately predicted based solely on
dy weight and composition given
t many factors affect body compo-
ion (21). Some sports dictate that
letes make changes in body weight
d composition that may not be best
the individual athlete. Athletes
o participate in weight-class
rts—such as wrestling or light-
ight rowing—may be required to
e or gain weight to qualify for a
cific weight category. Athletes who
rticipate in body conscious sports
ch as dance, gymnastics, figure
ating, or diving, may be pressured
lose weight and body fat to have a
n physique, although their current
ight for health and performance is
propriate. With extreme energy re-
ictions, losses of both muscle and
mass may adversely influence an
lete’s performance.
ndividualized assessment of an
lete’s body composition and body
ight or body image may be advan-
eous for improvement of athletic
rformance. Age, sex, genetics, and
requirements of the sport are fac-
s that influence an individual ath-
e’s body composition. An optimal
petitive body weight and relative
dy fatness should be determined
en an athlete is healthy and per-
ming at his or her best.
ethodology and equipment to per-
m body composition assessments
st be accessible and cost effective.
t all of the following methods meet
se criteria for the practitioner. In
dition, athletes and coaches should
ow that there are errors associated
th all body composition techniques
d that it is not appropriate to set a
cific body fat percentage goal for
individual athlete. Rather, a range
target percentages of body fat val-
s should be recommended.
essment Methodology
ree levels of assessment tech-
ues are used to assess body com-
sition (22). Direct assessment
sed on analysis of cadavers, al-
ugh not used in clinical practice, is
signated as a Level 1 technique.
e other two technique levels are
irect assessments (Level II) and
ubly indirect assessments (Level
). Hydrodensitometry, or underwa- Int
weighing, dual-energy x-ray ab-
ptiometry and air displacement
thysmography are Level II tech-
ues, and skinfold measurements
d bioelectrical impedance analysis
IA) are Level III techniques. Level
and Level III techniques are used
practice by sports dietitians.
nderwater weighing, once consid-
d the criterion standard, is no longer
mon. dual-energy x-ray absorpti-
etry, originally developed to assess
e mineral density, can be used for
y composition analysis (21). Al-
ugh dual-energy x-ray absorptiom-
y is fairly accurate, quick, and non-
asive, the cost of and access to the
trument limits its utility in practice.
displacement plethysmography
dPod, Life Measurement, Inc, Con-
d, CA) is also used to determine
y composition by body density (22),
d body fat percentage is calculated
ng the Siri (23) or Brozek and col-
gues (24) equations. Although this
thod provides valid and reliable as-
sment of body composition, it may
derestimate body fat in adults and
ldren by 2% to 3% (25).
wo of the most commonly used
vel III methods are skinfold mea-
rements and BIA. In addition to
asures of body weight, height,
ist and girth circumferences, skin-
d measurements are routinely used
sports dietitians to assess body
position. Usually, seven skinfold
es are used, including abdominal,
eps, front thigh, medial calf, sub-
pular, supraspinale, and triceps.
e standard techniques and defini-
ns of each of these sites are pro-
ed by Heymsfield and colleagues
d Marfell-Jones and colleagues
). Prediction equations using skin-
d measurements to determine body
content are numerous (22). Ap-
ximately 50% to 70% of the vari-
ce in body density is accounted for
this measurement. In addition,
pulation differences limit the abil-
to interchange the prediction
uations, standardization of skinfold
es varies, and skinfold measure-
nt techniques vary from investiga-
to investigator. Even the skinfold
iper is a source of variability (22).
spite the inherent problems of
infold measurement, this technique
ains a method of choice because it
convenient and inexpensive. The
Olympic Committee is using the
ernational Society for Advances in sig
March 2009 ● Journal o
nanthropometry techniques (26) as
orts are underway to standardize
asures worldwide. The US Olympic
mmittee advocates using the sum of
en skinfolds (millimeters) based on
ernational Society for Advances in
nanthropometry landmarks, mark-
skinfold sites on the body, reporting
plicate measures, and communicat-
the results as a range, rather than
centage body fat.
IA is based on the principle that
electrical signal is more easily con-
cted through lean tissue than fat or
ne (22). Fat mass is estimated by
btracting the BIA determined esti-
te of FFM from total body mass.
ole body resistance to the flow
an electrical current conducted
ough the body by electrodes placed
wrists and ankles can provide
rly accurate estimates of total body
ter and FFM (22). BIA is depen-
nt on a number of factors that can
se error in the measurement and
st be taken into account to obtain a
rly accurate estimate. Hydration
tus is the most important factor
t may alter the estimated percent-
e body fat. The prediction accuracy
BIA is similar to skinfold assess-
nts but BIA may be preferable be-
se it does not require the technical
ill associated with skinfold mea-
rements (27). Currently, upper and
er body impedance devices have
en developed but have not been
luated in an athletic population.
y Composition and Sportsformance
dy fat percentage of athletes varies
pending on the sex of the athlete
d the sport. The estimated minimal
el of body fat compatible with
alth is 5% for men and 12% for
men (22); however, optimal body
percentages for an individual ath-
e may be much higher than these
nimums and should be determined
an individual basis. The Interna-
nal Society for Advances in Kinan-
opometry sum of seven skinfolds
icates that the range of values for
athletic population is 30 to 60 mm
men and 40 to 90 mm for women
). Body composition analysis
ould not be used as a criterion for
ection of athletes for athletic
ms. Weight management inter-
tions should be thoughtfully de-
ned to avoid detrimental outcomes
f the AMERICAN DIETETIC ASSOCIATION 513
wi
as
lea
pra
ag
Con
rep
the
tio
hy
det
tw
ing
nifi
ma
Ev
ad
con
MA
EXE
At
tia
S
● oals
ould
ed
you
● on an
● exer ntio
● at m ot f
t.
S
● rain %
ved ting
rtion atin
● bu gua
incr tak
enti
● an
● eta
● an Ac
ed.
● ld b fore
is c
O
●
●
●
●
Fig
con
514
th specific regard for performance,
well as body composition (ie, loss of
n body mass). See Figure 3 for
ctical guidelines for weight man-
ement of athletes.
clusion Statement. Four studies have
orted inconclusive findings related to
effects of energy and protein restric-
n on athletic performance, but carbo-
drate restriction has been shown to be
rimental. For weight class athletes,
o studies showthatweight loss preced-
athletic competitionmay have no sig-
cant effect on measures of perfor-
nce, depending on refeeding protocol.
idence Grade III�Limited (www.
aevidencelibrary.com/conclusion.cfm?
clusion_statement_id�250448).
CRONUTRIENT REQUIREMENTS FOR
RCISE
hletes do not need a diet substan-
etting and monitoring goals
Set realistic weight and body composition g
� What is the maximum weight that you w
� What was the lowest weight you maintain
� How did you derive your goal weight?
� At what weight and body composition do
Encourage less focus on the scale and more
Monitor progress by measuring changes in
and general overall well-being.
Help athletes to develop lifestyle changes th
friends, for their parents, or to prove a poin
uggestions for food intake
Low energy intake will not sustain athletic t
weight loss without the athlete feeling depri
reducing intake of energy-dense snacks, po
If appropriate, athletes can reduce fat intake
energy balance (reduced energy intake and
total energy intake because some fat is ess
Emphasize increased intake of whole grains
Five or more daily servings of fruits and veg
Dieting athletes should not skimp on protein
and lean meats, fish, and poultry is suggest
A variety of fluids—especially water—shou
as a means of reaching a body-weight goal
ther weight management strategies
Advise athletes against skipping meals (esp
for times when they might get hungry, inclu
Athletes should not deprive themselves of fa
flexible and achievable. Athletes should rem
foods is discouraged.
Help athletes identify their own dietary weak
Remind athletes that they are making lifelon
going on a short-term diet.
ure 3. Weight management strategies for a
sequences? Women’s Health Issues. 1996;6:3
lly different from that recommended 60
March 2009 Volume 109 Number 3
the 2005Dietary Guidelines (16) and
ting Well with Canada’s Food Guide
). Although high-carbohydrate diets
ore than 60% of energy intake) have
n advocated in the past, caution is
ommended in using specific percent-
es as a basis for meal plans for ath-
es. For example, when energy intake
4,000 to 5,000 kcal/day, even a diet
taining 50% of energy from carbo-
drate will provide 500 to 600 g car-
ydrate (or approximately 7 to 8 g/kg
2 to 3.6 g/lb] for a 70-kg [154 lb] ath-
e), an amount sufficient to maintain
scle glycogen stores from day to day
). Similarly, if protein intake for this
n was 10% of energy intake, abso-
e protein intake (100 to 125 g/day)
ld exceed the recommended protein
ake for athletes (1.2 to 1.7 g/kg/day
84 to 119 g in a 70-kg athlete). Con-
sely, when energy intake is less
n 2,000 kcal/day, a diet providing
. Ask the athlete:
find acceptable?
without constant dieting?
perform best?
healthful habits such as stress management
cise performance and energy level, the preve
aintain a healthful weight for themselves—n
ing. Instead, decreases in energy intake of 10
or overly hungry. Strategies such as substitu
awareness, and doing activities other than e
t need to know that a lower-fat diet will not
eased energy expenditure) is achieved. Fat in
al for good health.
d cereals, and legumes.
bles provide nutrients and fiber.
d need to maintain adequate calcium intakes.
e consumed throughout the day, including be
ontraindicated.
lly breakfast) and allowing themselves to bec
g keeping nutritious snacks available for those
ite foods or set unrealistic dietary rules or gu
er that all foods can fit into a healthful lifesty
ses and plan strategies for dealing with them
ietary changes to sustain a healthful weight a
tes. (Adapted from: Manore MM. Chronic d
-341. Copyright 1996, with permission from E
% of energy from carbohydrate may cis
t be sufficient to maintain optimal
bohydrate stores (4 to 5 g/kg or 1.8
2.3 g/lb) in a 60-kg (132 lb) athlete.
tein
otein metabolism during and fol-
ing exercise is affected by sex, age,
ensity, duration, and type of exer-
e, energy intake, and carbohydrate
ailability. More detailed reviews of
se factors and their relationship to
tein metabolism and needs of ac-
e individuals can be found else-
ere (30,31). The current RDA is 0.8
g body weight and the Acceptable
cronutrient Distribution Range for
tein intake for adults older than
e 18 years is 10% to 35% of total
ergy (15). Because there is not a
ong body of evidence documenting
t additional dietary protein is
eded by healthy adults who under-
e endurance or resistance exer-
d making good food choices.
n of injuries, normal menstrual function,
or their sport, for their coach, for their
to 20% of normal intake will lead to
lower-fat foods for whole-fat foods,
g when not hungry can be useful.
rantee weight loss unless a negative
e should not be decreased below 15% of
cordingly, use of low-fat dairy products
, during, and after exercise. Dehydration
overly hungry. They should be prepared
es.
ines. Instead, dietary goals should be
Developing list of “good” and “bad”
optimal nutritional status rather than
g in active women: What are the health
ier.)
in
Ea
(28
(m
bee
rec
ag
let
is
con
hy
boh
[3.
let
mu
(29
pla
lut
cou
int
or
ver
tha
no
car
to
Pro
Pr
low
int
cis
av
the
pro
tiv
wh
g/k
Ma
pro
ag
en
str
tha
ne
tak
ecia ome
din tim
vor idel
emb le.
nes .
g d nd
thle ietin
32 lsev
e, the current Dietary Reference
Int
do
un
div
Ho
tak
tai
com
End
tei
cis
stu
me
rec
ing
su
ne
in
to
me
tho
tha
mo
an
en
con
or
exe
at,
da
su
ula
exp
tab
spa
oxi
ne
con
en
spo
Str
ma
ces
for
tio
pa
cie
(30
ear
the
siz
ne
be
res
pro
me
tra
ma
Pro
Hi
thr
inv
su
am
ha
pro
are
na
tal
tra
con
str
en
ga
cau
me
itiv
(41
pro
va
mi
the
cis
is
nu
ath
pro
ple
Fat
Fa
ma
tia
ass
A,
nu
20
20
Ea
Gu
tha
fat
po
sat
sen
fol
tio
su
su
�7
pe
thi
VIT
Mi
rol
syn
he
an
tiv
sis
rec
pa
req
res
tio
ne
cre
mi
res
en
cre
an
ath
T
mi
ath
mi
ma
da
car
let
nu
en
los
mo
die
low
ath
mu
Us
me
in
all
B V
Pan
Ad
po
pro
pa
com
fun
Th
ine
are
du
lat
du
syn
ma
ne
rib
are
die
tar
ter
L
du
inc
vit
tha
for
akes for protein and amino acids
es not specifically recognize the
ique needs of routinely active in-
iduals and competitive athletes.
wever, recommending proteinin-
es in excess of the RDA to main-
n optimum physical performance is
monly done in practice.
urance Athletes. An increase in pro-
n oxidation during endurance exer-
e, coupled with nitrogen balance
dies, provides the basis for recom-
nding increased protein intakes for
overy from intense endurance train-
(32). Nitrogen balance studies
ggest that dietary protein intake
cessary to support nitrogen balance
endurance athletes ranges from 1.2
1.4 g/kg/day (29-31). These recom-
ndations remain unchanged even
ugh recent studies have shown
t protein turnover may become
re efficient in response to endur-
ce exercise training (29,32). Ultra-
durance athletes who engage in
tinuous activity for several hours
consecutive days of intermittent
rcise should also consume protein
or slightly above 1.2 to 1.4 g/kg/
y (32). Energy balance, or the con-
mption of adequate energy, partic-
rly carbohydrates, to meet those
ended, is important to protein me-
olism so that amino acids are
red for protein synthesis and not
dized to assist in meeting energy
eds (33,34). In addition, discussion
tinues as to whether sex differ-
ces in protein-related metabolic re-
nses to exercise exist (35,36).
ength Athletes. Resistance exercise
y necessitate protein intake in ex-
s of the RDA, as well as that needed
endurance exercise, because addi-
nal protein, essential amino acids in
rticular, is needed along with suffi-
nt energy to support muscle growth
,31). This is particularly true in the
ly phase of strength training when
most significant gains in muscle
e occurs. The amount of protein
eded to maintain muscle mass may
lower for individuals who routinely
istance train due to more efficient
tein utilization (30,31). Recom-
nded protein intakes for strength-
ined athletes range from approxi-
tely 1.2 to 1.7 g/kg/day (30,32).
tein and Amino Acid Supplements.
gh-protein diets have been popular
oughout history. Although earlier
estigations in this area involved erc
pplementation with individual
ino acids (37,38) more recent work
s shown that intact, high-quality
teins such as whey, casein, or soy
effectively used for the mainte-
nce, repair, and synthesis of skele-
muscle proteins in response to
ining (39). Protein or amino acids
sumed in close proximity to
ength and endurance exercise can
hance maintenance of, and net
ins in, skeletal muscle (39,40). Be-
se protein or amino acid supple-
ntation has not been shown to pos-
ely influence athletic performance
,42), recommendations regarding
tein supplementation are conser-
tive and directed primarily at opti-
zing the training response to and
recovery period following exer-
e. From a practical perspective, it
important to conduct a thorough
trition assessment specific to an
lete’s goals before recommending
tein powders and amino acid sup-
ments to athletes.
t is a necessary component of a nor-
l diet, providing energy and essen-
l elements of cell membranes and
ociated nutrients such as vitamins
D, and E. The Acceptable Macro-
trient Distribution Range for fat is
% to 35% of energy intake (17). The
05 Dietary Guidelines (16) and
ting Well with Canada’s Food
ide (28) make recommendations
t the proportion of energy from
ty acids be 10% saturated, 10%
lyunsaturated, and 10% monoun-
urated and include sources of es-
tial fatty acids. Athletes should
low these general recommenda-
ns. Careful evaluation of studies
ggesting a positive effect of con-
ming diets for which fat provides
0% of energy intake on athletic
rformance (43,44) does not support
s concept (45).
AMINS AND MINERALS
cronutrients play an important
e in energy production, hemoglobin
thesis, maintenance of bone
alth, adequate immune function,
d protection of body against oxida-
e damage. They assist with synthe-
and repair of muscle tissue during
overy from exercise and injury. Ex-
ise stresses many of the metabolic the
March 2009 ● Journal o
thways where micronutrients are
uired, and exercise training may
ult in muscle biochemical adapta-
ns that increase micronutrient
eds. Routine exercise may also in-
ase the turnover and loss of these
cronutrients from the body. As a
ult, greater intakes of micronutri-
ts may be required to cover in-
ased needs for building, repair,
d maintenance of lean body mass in
letes (46).
he most common vitamins and
nerals found to be of concern in
letes’ diets are calcium and vita-
n D, the B vitamins, iron, zinc,
gnesium, as well as some antioxi-
nts such as vitamins C and E, beta
otene, and selenium (46-50). Ath-
es at greatest risk for poor micro-
trient status are those who restrict
ergy intake or have severe weight
s practices, who eliminate one or
re of the food groups from their
t, or who consume unbalanced and
micronutrient-dense diets. These
letes may benefit from a daily
ltivitamin/mineral supplement.
e of vitamin and mineral supple-
nts does not improve performance
individuals consuming nutrition-
y adequate diets (46-48,50).
itamins: Thiamin, Riboflavin, Niacin, B-6,
tothenic Acid, Biotin, Folate, and B-12
equate intake of B vitamins is im-
rtant to ensure optimum energy
duction and the building and re-
ir of muscle tissue (48,51). The B-
plex vitamins have two major
ctions directly related to exercise.
iamin, riboflavin, niacin, pyridox-
(B-6), pantothenic acid, and biotin
involved in energy production
ring exercise (46,51), whereas fo-
e and B-12 are required for the pro-
ction of red blood cells, for protein
thesis, and in tissue repair and
intenance including the central
rvous system. Of the B vitamins,
oflavin, pyridoxine, folate and B-12
frequently low in female athletes’
ts, especially those who are vege-
ian or have disordered eating pat-
ns (47,48).
imited research has been con-
cted to examine whether exercise
reases the need for the B-complex
amins (46,48). Some data suggest
t exercise may increase the need
these vitamins as much as twice
current recommended amount
f the AMERICAN DIETETIC ASSOCIATION 515
(48
can
erg
ma
ha
for
fol
an
(46
tha
am
su
for
Vit
Vit
cal
ru
an
mi
an
tem
let
wh
ou
fig
tam
no
mi
wo
wi
en
for
A
cat
ad
An
Car
Th
an
pla
me
Be
con
bee
cis
str
(49
me
ma
by
bee
an
per
tra
ope
tha
erc
da
Th
da
per
gre
tak
res
die
an
T
of
da
he
an
ery
un
ge
reg
no
an
ne
mi
sh
du
an
str
som
att
da
cer
mo
let
th
for
do
po
V
pe
die
thi
pro
inc
ica
wi
fic
ha
cis
vit
Min
Ma
Th
of
are
siu
era
tio
(55
Cal
tan
pa
blo
mu
qu
inc
de
ath
bo
tak
oth
qu
me
(47
S
vit
nu
me
de
for
ele
of
Iro
tio
mo
zym
(50
ess
we
vou
tem
sto
nu
ath
de
can
wo
qu
pec
cre
At
blo
tak
(ie
me
T
am
ina
tor
veg
av
tra
iro
str
foo
na
esp
ne
sho
ses
B
an
is
ter
mi
516
); however, these increased needs
generally be met with higher en-
y intakes. Although short-term
rginal deficiencies of B vitamins
ve not been observed to affect per-
mance, severe deficiency of B-12,
ate, or both may result in anemia
d reduced endurance performance
,47,52). Therefore, it is important
t athletes consume adequate
ounts of these micronutrients to
pport their efforts for optimal per-
mance and health.
amin D
amin D is required for adequate
cium absorption, regulation of se-
m calcium and phosphorus levels,
d promotion of bone health. Vita-
n D also regulates the development
d homeostasis of the nervous sys-
and skeletal muscle (53-55). Ath-
es who live at northern latitudes or
o train primarily indoors through-
t the year, such as gymnasts and
ure skaters, are at risk for poor vi-
in D status, especially if they do
t consume foods fortified with vita-
n D (50,56,57). These athletes
uld benefit from supplementation
th vitamin D at the Dietary Refer-
ce Intake level (5 �g/day or 200 IU
ages 19 to 49years) (54,56,58-61).
growing number of experts advo-
e that the RDA for vitamin D is not
equate (53,62,63).
tioxidants: Vitamins C and E, Beta
otene, and Selenium
e antioxidant nutrients, vitamins C
d E, beta carotene, and selenium,
y important roles in protecting cell
mbranes from oxidative damage.
cause exercise can increase oxygen
sumption by 10- to 15-fold, it has
n hypothesized that chronic exer-
e produces a constant “oxidative
ess” on the muscles and other cells
) leading to lipid peroxidation of
mbranes. Although acute exercise
y increase levels of lipid peroxide
products (64), habitual exercise has
n shown to result in an augmented
tioxidant system and reduced lipid
oxidation (50,65). Thus, a well-
ined athlete may have a more devel-
d endogenous antioxidant system
n a sedentary person. Whether ex-
ise increases the need for antioxi-
nt nutrients remains controversial.
ere is little evidence that antioxi- an
March 2009 Volume 109 Number 3
nt supplements enhance physical
formance (49,50,64,66). Athletes at
atest risk for poor antioxidant in-
es are those following a low-fat diet,
tricting energy intakes, or limiting
tary intakes of fruits, vegetables,
d whole grains (29,66).
he evidence that a combination
antioxidants or single antioxi-
nts such as vitamin E may be
lpful in reducing inflammation
d muscle soreness during recov-
from intense exercise remains
clear (42,67). Although the ergo-
nic potential of vitamin E with
ard to physical performance has
t been clearly documented, endur-
ce athletes may have a higher
ed for this vitamin. Indeed, vita-
n E supplementation has been
own to reduce lipid peroxidation
ring aerobic/endurance exercise
d have a limited effect with
ength training (66). There is
e evidence that vitamin E may
enuate exercise-induced DNA
mage and enhance recovery in
tain active individuals; however,
re research is needed (66). Ath-
es should be advised not to exceed
e Tolerable Upper Intake Levels
antioxidants because higher
ses could be pro-oxidative with
tential negative effects (46,64,68).
itamin C supplements do not ap-
ar to have an ergogenic effect if the
t provides adequate amounts of
s nutrient. Because strenuous and
longed exercise has been shown to
rease the need for vitamin C, phys-
l performance can be compromised
th marginal vitamin C status or de-
iency. Athletes who participate in
bitual prolonged, strenuous exer-
e should consume 100 to 1,000 mg
amin C daily (47,69,70).
erals: Calcium, Iron, Zinc, and
gnesium
e primary minerals low in the diets
athletes, especially female athletes,
calcium, iron, zinc, and magne-
m (47). Low intakes of these min-
ls are often due to energy restric-
n or avoidance of animal products
).
cium. Calcium is especially impor-
t for growth, maintenance, and re-
ir of bone tissue; maintenance of
od calcium levels, regulation of
scle contraction, nerve conduction,
d normal blood clotting. Inade- ple
ate dietary calcium and vitamin D
rease the risk of low bone-mineral
nsity and stress fractures. Female
letes are at greatest risk for low
ne-mineral density if energy in-
es are low, dairy products and
er calcium-rich foods are inade-
ate or eliminated from the diet, and
nstrual dysfunction is present
,52,55,71-73).
upplementation with calcium and
amin D should be determined after
trition assessment. Current recom-
ndations for athletes with disor-
red eating, amenorrhea, and risk
early osteoporosis are 1,500 mg
mental calcium and 400 to 800 IU
vitamin D per day (50,72,73).
n. Iron is required for the forma-
n of oxygen-carrying proteins, he-
globin and myoglobin, and for en-
es involved in energy production
,74). Oxygen carrying capacity is
ential for endurance exercise as
ll as normal function of the ner-
s, behavioral, and immune sys-
s (64,74). Iron depletion (low iron
res) is one of the most prevalent
trient deficiencies observed among
letes, especially women (75). Iron
ficiency, with or without anemia,
impair muscle function and limit
rk capacity (47,58,75,76). Iron re-
irements for endurance athletes, es-
ially distance runners, are in-
ased by approximately 70% (58,74).
hletes who are vegetarian or regular
od donors should aim for an iron in-
e greater than their respective RDA
,�18 mg and�8 mg, for women and
n, respectively) (58,75).
he high incidence of iron depletion
ong athletes is usually attributed to
dequate energy intake. Other fac-
s that can affect iron status include
etarian diets that have poor iron
ailability, periods of rapid growth,
ining at high altitudes, increased
n losses in sweat, feces, urine, men-
ual blood, intravascular hemolysis,
t-strike hemolysis, regular blood do-
tion, or injury (50,75,77). Athletes,
ecially women, long-distance run-
rs, adolescents, and vegetarians
uld be screened periodically to as-
s andmonitor iron status (75,77,78).
ecause reversing iron deficiency
emia can require 3 to 6 months, it
advantageous to begin nutrition in-
vention before iron deficiency ane-
a develops (47,75). Although de-
ted iron stores (low serum ferritin)
are
let
an
of
(50
wi
fro
ne
me
pro
mo
S
tra
an
tra
qu
um
an
tri
ap
to
tiv
I
iro
pro
an
wo
cre
he
con
Th
wh
an
me
pro
pro
mu
me
fer
pro
an
du
red
im
Zin
bu
en
tus
in
tic
zin
be
ho
an
ne
pe
cat
Am
rec
let
ris
of
dif
ses
tab
tio
bo
car
str
no
To
is
tio
ple
thi
su
hig
an
ing
su
mo
tat
no
Ma
of
col
an
ne
mu
Ma
an
req
exe
bod
tlin
nis
ad
sho
sou
low
tio
Sod
So
ula
los
let
To
diu
g/d
diu
(0.
dra
esp
ho
P
ele
sio
Du
siu
les
in
nu
ad
tas
HY
Be
con
pe
inc
thr
str
hy
exe
bo
exe
ho
cog
T
Me
an
a
sea
ma
ing
the
ici
spe
dit
the
the
Flu
Bef
exe
ab
3 m
Th
tim
tio
pe
the
(eg
gre
voi
vid
ma
Th
(83
Du
pro
rad
by
en
for
los
wi
atu
he
bol
an
fro
more prevalent in female ath-
es, the incidence of iron deficiency
emia in athletes is similar to that
the nonathlete female population
,75,77). Chronic iron deficiency,
th or without anemia, that results
m consistently poor iron intake can
gatively affect health, physical and
ntal performance, and warrants
mpt medical intervention and
nitoring (76,78).
ome athletes may experience a
nsient decrease in serum ferritin
d hemoglobin at the initiation of
ining due to hemodilution subse-
ent to an increase in plasma vol-
e known as “dilutional” or “sports
emia” and may not respond to nu-
tion intervention. These changes
pear to be a beneficial adaptation
aerobic training that do not nega-
ely affect performance (50).
n athletes who are iron deficient,
n supplementation not only im-
ves blood biochemical measures
d iron status but also increases
rk capacity as evidenced by in-
asing oxygen uptake, reducing
art rate, and decreasing lactate
centration during exercise (47).
ere is some evidence that athletes
o are iron deficient but do not have
emia may benefit from iron supple-
ntation (50,75). Recent findings
vide additional support for im-
ved performance (eg, less skeletal
scle fatigue) when iron supple-
ntation was prescribed as 100 mg
rous sulfate for 4-6 weeks (76). Im-
ving work capacity and endur-
ce, increasing oxygen uptake, re-
ced lactate concentrations, and
uced muscle fatigue are benefits of
proved iron status (50).
c. Zinc plays a role in growth,
ilding and repair of muscle tissue,
ergy production, and immune sta-
. Diets low in animal protein, high
fiber, and vegetarian diets, in par-
ular, are associated with decreased
c intake (50,52). Zinc status has
en shown to directly affect thyroid
rmone levels, basal metabolic rate,
d protein use, which in turn can
gatively affect health and physical
rformance (50). Survey data indi-
e that a large number of North
ericans have zinc intakes below
ommended levels(74,75,79). Ath-
es, particularly women, are also at
k for zinc deficiency (79). The affect
low zinc intakes on zinc status is an
ficult to measure because clear as-
sment criteria have not been es-
lished and plasma zinc concentra-
ns may not reflect changes in whole
dy zinc status (47,79). Decreases in
diorespiratory function, muscle
ength, and endurance have been
ted with poor zinc status (47). The
lerable Upper Intake Level for zinc
40 mg (74). Athletes should be cau-
ned against single dose zinc sup-
ments because they often exceed
s amount and unnecessary zinc
pplementation may lead to low
h-density lipoprotein cholesterol
d nutrient imbalances by interfer-
with absorption of other nutrients
ch as iron and copper (47). Further-
re, the benefits of zinc supplemen-
ion to physical performance have
t been established.
gnesium. Magnesium plays a variety
roles in cellular metabolism (eg, gly-
ysis, fat, and protein metabolism),
d regulates membrane stability and
uromuscular, cardiovascular, im-
ne, and hormonal functions (47,55).
gnesium deficiency impairs endur-
ce performance by increasing oxygen
uirements to complete submaximal
rcise. Athletes in weight-class and
y conscious sports such as wres-
g, ballet, gymnastics, as well as ten-
, have been reported to consume in-
equate dietary magnesium. Athletes
uld be educated about good food
rces of magnesium. In athletes with
magnesium status, supplementa-
n might be beneficial (47).
ium, Chloride, and Potassium
dium is a critical electrolyte, partic-
rly for athletes with high sweat
ses (80-83). Many endurance ath-
es will require much more than the
lerable Upper Intake Level for so-
m (2.3 g/day) and chloride (3.6
ay). Sports drinks containing so-
m (0.5 to 0.7 g/L) and potassium
8 to 2.0 g/L), as well as carbohy-
te, are recommended for athletes
ecially in endurance events (�2
urs) (50,80,82,83).
otassium is important for fluid and
ctrolyte balance, nerve transmis-
n, and active transport mechanisms.
ring intense exercise, plasma potas-
m concentrations tend to decline to a
ser degree than sodium. A diet rich
a variety of fresh vegetables, fruits,
ts and seeds, dairy foods, leanmeats,
d whole grains is usually considered lite
March 2009 ● Journal o
equate for maintaining normal po-
sium status among athletes (32,83).
DRATION
ing well hydrated is an important
sideration for optimal exercise
rformance. Because dehydration
reases the risk of potentially life-
eatening heat injury such as heat
oke, athletes should strive for eu-
dration before, during, and after
rcise. Dehydration (loss of �2%
dy weight) can compromise aerobic
rcise performance, particularly in
t weather, and may impair mental/
nitive performance (83).
he American College of Sports
dicine’s Position Stand on Exercise
d Fluid Replacement (83) provides
comprehensive review of the re-
rch and recommendations for
intaining hydration before, dur-
, and after exercise. In addition,
American College of Sports Med-
ne has published position stands
cific to special environmental con-
ions (84,85). The major points from
se position stands are the basis for
following recommendations.
id and Electrolyte Recommendations
ore Exercise. At least 4 hours before
rcise, individuals should drink
out 5 to 7 mL/kg body weight (�2 to
L/lb) of water or a sport beverage.
is would allow enough time to op-
ize hydration status and for excre-
n of any excess fluid as urine. Hy-
rhydration with fluids that expand
extra- and intracellular spaces
, water and glycerol solutions) will
atly increase the risk of having to
d during competition (83) and pro-
es no clear physiologic or perfor-
nce advantage over euhydration.
is practice should be discouraged
).
ring Exercise. Athletes dissipate heat
duced during physical activity by
iation, conduction, convection, and
vaporization of water. In hot, dry
vironments, evaporation accounts
more than 80% of metabolic heat
s. Sweat rates for any given activity
ll vary according to ambient temper-
re, humidity, body weight, genetics,
at acclimatization state, and meta-
ic efficiency. Depending on the sport
d condition, sweat rates can range
m as little as 0.3 to as much as 2.4
rs per hour (83). In addition to wa-
f the AMERICAN DIETETIC ASSOCIATION 517
ter
va
ag
ap
tho
Th
siu
suc
sw
T
cis
ces
am
is
let
an
ers
leg
for
to
wo
ize
(83
an
ass
sw
pla
ath
C
ing
can
ba
for
an
me
for
tai
rep
wh
flu
pro
6%
me
lon
F
alw
sw
em
ab
flu
erc
be
sor
ma
in
wi
hy
D
lyt
inc
an
du
flu
Alt
erc
an
som
com
cau
ses
dra
pre
is m
a s
tio
pe
wr
an
ath
be
hy
tio
ur
an
ma
pa
da
(84
H
cen
L])
sw
diu
po
in
lea
su
aft
S
ate
de
he
pla
dra
ula
tic
pa
cyc
soc
su
cle
cu
cro
pla
com
pe
(83
Aft
do
exe
com
dra
qu
an
lyt
com
hy
dri
67
kg
cis
ag
wi
los
Spe
Hot
for
cre
en
tem
tur
dia
dis
sw
the
a v
tem
hig
de
tak
ath
ple
for
Col
hy
we
de
clu
as
lat
exe
be
If
flu
ma
mu
ma
som
the
tak
Alt
soc
ma
(8,
diu
los
pe
be
in
wo
hig
da
tio
518
, sweat also contains substantial but
riable amounts of sodium. The aver-
e concentration of sodium in sweat
proximates 1 g/L (50 mmol/L) (al-
ugh concentrations vary widely).
ere are modest amounts of potas-
m and small amounts of minerals
h as magnesium and chloride lost in
eat.
he intent of drinking during exer-
e is to avert a water deficit in ex-
s of 2% of body weight. The
ount and rate of fluid replacement
dependent on an individual ath-
e’s sweat rate, exercise duration,
d opportunities to drink (83). Read-
are referred to the American Col-
e of Sports Medicine position stand
specific recommendations related
body size, sweat rates, types of
rk, and encouraged to individual-
hydration protocols when possible
). Routine measurement of pre-
d postexercise body weights will
ist practitioners in determining
eat rates and customizing fluid re-
cement programs for individual
letes (83).
onsumption of beverages contain-
electrolytes and carbohydrates
help sustain fluid and electrolyte
lance and endurance exercise per-
mance (83). The type, intensity,
d duration of exercise and environ-
ntal conditions will alter the need
fluids and electrolytes. Fluids con-
ning sodium and potassium help
lace sweat electrolyte losses,
ereas sodium stimulates thirst and
id retention, and carbohydrates
vide energy. Beverages containing
to 8% carbohydrate are recom-
nded for exercise events lasting
ger than 1 hour (83).
luid balance during exercise is not
ays possible because maximal
eat rates exceed maximal gastric
ptying rates that in turn limit fluid
sorption and most often rates of
id ingestion by athletes during ex-
ise fall short of amounts that can
emptied from the stomach and ab-
bed by the gut. Gastric emptying is
ximized when the amount of fluid
the stomach is high and reduced
th hypertonic fluids or when carbo-
drate concentration is �8%.
isturbances of fluid and electro-
e balance that can occur in athletes
lude dehydration, hypohydration,
d hyponatremia (83). Exercise-in-
ced dehydration develops because
id losses that exceed fluid intake. sta
March 2009 Volume 109 Number 3
hough some individuals begin ex-
ise euhydrated and dehydrate over
extended duration, athletes in
e sports might start training or
petition in a dehydrated state be-
se the interval between exercise
sions is inadequate for full rehy-
tion (82). Another factor that may
dispose an athlete to dehydration
aking weight as a prerequisite for
pecific sport or event. Hypohydra-
n, a practice of some athletes com-
ting in weight class sports (eg,
estling, boxing, lightweight crew,
d martial arts), can occur when
letes dehydrate themselves before
ginning a competitive event. Hypo-
dration candevelop by fluid restric-
n, certain exercise practices, di-
etic use, or sauna exposure before
event. In addition, fluid deficits
y span workouts for athletes who
rticipate in multiple or prolonged
ily sessions of exercise in the heat
).
yponatremia (serum sodium con-
tration �130 mEq/L [�130 mmol/
can result from prolonged, heavy
eating with failure to replace so-
m, or excessive water intake. Hy-
natremia is more likely to develop
novice marathoners who are not
n, run slowly, sweat less or con-
me excess water before, during, or
er an event (83).
keletal muscle cramps are associ-
d with dehydration, electrolyte
ficits, and muscle fatigue. Non–
at acclimatized American football
yers commonly experience dehy-
tion and muscle cramping partic-
rly during formal preseason prac-
e sessions in late summer. Athletes
rticipating in tennis matches, long
ling races, late-season triathlons,
cer, and beach volleyball are also
sceptible to dehydration and mus-
cramping. Muscle cramps also oc-
r in winter-sport athletes such as
ss-country skiers and ice-hockey
yers. Muscle cramps are more
mon in profuse sweaters who ex-
rience large sweat sodium losses
).
er Exercise. Because many athletes
not consume enough fluids during
rcise to balance fluid losses, they
plete their exercise session dehy-
ted to some extent. Given ade-
ate time, intake of normal meals
d beverages will restore hydration
tus by replacing fluids and electro- �1
es lost during exercise. Rapid and
plete recovery from excessive de-
dration can be accomplished by
nking at least 16 to 24 oz (450 to
5 mL) of fluid for every pound (0.5
) of body weight lost during exer-
e. Consuming rehydration bever-
es and salty foods at meals/snacks
ll help replace fluid and electrolyte
ses (83).
cial Environmental Conditions
and Humid Environments. The risk
dehydration and heat injury in-
ases dramatically in hot, humid
vironments (84). When the ambient
perature exceeds body tempera-
e, heat cannot be dissipated by ra-
tion. Moreover, the potential to
sipate heat by evaporation of
eat is substantially reduced when
relative humidity is high. There is
ery high risk of heat illness when
perature and humidity are both
h. If competitive events occur un-
r these conditions, it is necessary to
e every precaution to assure that
letes are well hydrated, have am-
access to fluids, and are monitored
heat-related illness.
d Environments. It is possible for de-
dration to occur in cool or cold
ather (85). Factors contributing to
hydration in cold environments in-
de respiratory fluid losses, as well
sweat losses that occur when insu-
ed clothing is worn during intense
rcise. Dehydration can also occur
cause of low rates of fluid ingestion.
an athlete is chilled and available
ids are cold, the incentive to drink
y be reduced. Finally, removal of
ltiple layers of clothing to urinate
y be inconvenient and difficult for
e athletes, especially women, and
y may voluntarily limit fluid in-
e (86).
itude. Fluid losses beyond those as-
iated with any exercise performed
y occur at altitudes �2,500 m
200 ft) consequent to mandatory
resis and high respiratory water
ses, accompanied by decreased ap-
tite. Respiratory water losses may
as high as 1,900 mL (1.9 L) per day
men and 850 mL (0.85 L) per day in
men (87,88). Total fluid intake at
h altitude approaches 3 to 4 L per
y to promote optimal kidney func-
n and maintain urine output of
.4 L in adults (87).
THE
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an
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me
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TRAINING DIET
e fundamental differences between
athlete’s diet and that of the gen-
l population are that athletes re-
ire additional fluid to cover sweat
ses and additional energy to fuel
ysical activity. As discussed ear-
r, it is appropriate for much of the
ditional energy to be supplied as
bohydrate. The proportional in-
ase in energy requirements ap-
ars to exceed the proportional in-
ase in needs for most other
trients. Accordingly, as energy re-
irements increase, athletes should
st aim to consume the maximum
mber of servings appropriate for
ir needs from carbohydrate-based
d groups (ie, bread, cereals and
ins, legumes, milk/alternatives,
etables, and fruits). Energy needs
many athletes will exceed the
ount of energy (kilocalories per
y) in the upper range of servings for
se food groups. Conversely, ath-
es who are small and/or have lower
ergy needs will need to pay greater
ention to making nutrient-dense
d choices to obtain adequate carbo-
drate, protein, essential fats, and
cronutrients.
ith regard to the timing of meals
d snacks, common sense dictates
t food and fluid intake around
rkouts be determined on an indi-
ual basis with consideration for an
lete’s gastrointestinal characteris-
s as well as the duration and inten-
y of the workout. For example, an
lete might tolerate a snack con-
ting of milk and a sandwich 1 hour
fore a low-intensity workout, but
uld be uncomfortable if the same
al was consumed before a very
rd effort. Athletes in heavy train-
or doing multiple daily workouts
y need to eat more than three
als and three snacks per day and
ould consider every possible eating
asion. These athletes should con-
er eating in close proximity to the
d of a workout, having more than
e afternoon snack, or eating a sub-
ntial snack before bed.
clusion Statement. Twenty-three stud-
investigating consumption of a range
acronutrient composition during the
ining period on athletic performance
re evaluated. Nine studies have re-
ted that the consumption of a high
bohydrate diet (�60% of energy) dur-
the training period and the week be- 98
e competition results in improved
scle glycogen concentrations and/or
nificant improvements in athletic per-
mance. Two studies reported no addi-
nal performance benefits when con-
ing levels above 6 g carbohydrate/kg
y weight. Two studies report sex dif-
ences; womenmay have less ability to
rease muscle glycogen concentrations
ough increased carbohydrate con-
ption, especially when energy intake
insufficient. One study based on the
sumption of a high-fat diet (�65% of
rgy) for 10 days followed by a high-
bohydrate diet (�65% of energy) for 3
ys reported a significant improvement
athletic performance. Nine studies re-
t no significant effects of macronutri-
composition on athletic performance
ring the training period and week
or to competition. Evidence Grade
Fair (www.adaevidencelibrary.com/
clusion.cfm?conclusion_statement_
250447).
-Exercise Meal
ting before exercise, as opposed to
rcising in the fasting state, has been
wn to improve performance (89,90).
e meal or snack consumed before
petition or an intense workout
uld prepare athletes for the upcom-
activity, and leave the individual
ither hungry nor with undigested
d in the stomach. Accordingly, the
lowing general guidelines for meals
d snacks should be used: sufficient
id should be ingested to maintain
dration, foods should be relatively
in fat and fiber to facilitate gastric
ptying and minimize gastrointesti-
l distress, high in carbohydrate to
intain blood glucose and maximizecogen stores, moderate in protein,
d familiar to the athlete.
he size and timing of the pre-ex-
ise meal are interrelated. Because
st athletes do not like to compete
a full stomach, smaller meals
ould be consumed in closer proxim-
to the event to allow for gastric
ptying, whereas larger meals can
consumed when more time is avail-
le before exercise or competition.
ounts of carbohydrate shown to
hance performance have ranged
m approximately 200 to 300 g car-
hydrate for meals consumed 3 to 4
urs before exercise. Studies report
her no effect or beneficial effects of
-event feeding on performance (91-
). Data are equivocal concerning Co
March 2009 ● Journal o
ether the glycemic index of carbo-
drate in the pre-exercise meal af-
ts performance (92,99-102).
lthough the above guidelines are
nd and effective, the athlete’s in-
idual needs must be emphasized.
me athletes consume and enjoy a
bstantial meal (eg, pancakes, juice,
d scrambled eggs) 2 to 4 hours be-
e exercise or competition; however,
ers may suffer severe gastrointes-
al distress following such a meal
d need to rely on liquid meals. Ath-
es should always ensure that they
ow what works best for themselves
experimenting with new foods and
verages during practice sessions
d planning ahead to ensure they
ll have access to these foods at the
propriate time.
clusion Statement. Nineteen studies
estigating the consumption of a range
acronutrient composition during the
hours before competition on athletic
formance were evaluated. Of eight
dies, six reported no significant effect
meal consumption 90 minutes to 4
rs before trials on athletic perfor-
nce. Six studies that focused on the
sumption of food or beverage within
hour before competition reported no
nificant effects on athletic perfor-
nce, despite hyperglycemia, hyper-
ulinemia, increased carbohydrate
dation, and reduced free fatty acid
ilability.Variations in researchmeth-
logy on glycemic index of meals con-
ed prior to competition have led to
onclusive findings. Evidence Grade
Fair (www.adaevidencelibrary.com/
clusion.cfm?conclusion_statement_
250452).
ring Exercise
rrent research supports the ben-
t of carbohydrate consumption in
ounts typically provided in sport
inks (6% to 8%) to endurance per-
mance in events lasting 1 hour or
s (103-105), especially in athletes
o exercise in the morning after an
ernight fast when liver glycogen
els are decreased. Providing exog-
ous carbohydrate during exercise
lps maintain blood glucose levels
d improve performance (106).
or longer events, consuming 0.7 g
bohydrate/kg body weight per hour
proximately 30 to 60 g per hour) has
n shown unequivocally to extend
durance performance (107,108).
nsuming carbohydrates during ex-
f the AMERICAN DIETETIC ASSOCIATION 519
erc
ati
hy
exe
int
int
on
am
aft
eff
am
thr
(10
sh
tos
cau
glu
su
fec
of
the
see
pre
oth
bo
con
wh
flu
tai
Con
inv
of
com
we
car
cis
con
ma
car
cis
rep
an
pro
ide
dit
exe
stu
exe
dra
ges
Ev
ad
con
Rec
Th
po
or
int
wh
an
wi
wi
gly
de
low
cau
tho
rac
the
po
the
let
in
wo
ma
ses
su
me
T
dra
sis
su
mi
car
up
res
exe
lay
sar
da
sio
wi
me
dr
ho
bou
me
en
ath
an
T
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520
ise is even more important in situ-
ons when athletes have not carbo-
drate-loaded, not consumed pre-
rcise meals, or restricted energy
ake for weight loss. Carbohydrate
ake should begin shortly after the
set of activity; consuming a given
ount of carbohydrate as a bolus
er 2 hours of exercise is not as
ective as consuming the same
ount at 15 to 20 minute intervals
oughout the 2 hours of activity
9). The carbohydrate consumed
ould yield primarily glucose; fruc-
e alone is not as effective and may
se diarrhea, although mixtures of
cose and fructose, other simple
gars and maltodextrins, appear ef-
tive (107). If the same total amount
carbohydrate and fluid is ingested,
form of carbohydrate does not
m to matter. Some athletes may
fer to use a sport drink whereas
ers may prefer to consume a car-
hydrate snack or sports gel and
sume water. As described else-
ere in this document, adequate
id intake is also essential for main-
ning endurance performance.
clusion Statement. Thirty-six studies
estigating the consumption of a range
macronutrient composition during
petition on athletic performance
re evaluated. Seven studies based on
bohydrate consumption during exer-
e lasting less than 60 minutes show
flicting results on athletic perfor-
nce. However, of 17 studies based on
bohydrate consumption during exer-
e lasting greater than 60minutes, five
orted improved metabolic response,
d seven of 12 studies reported im-
vements in athletic performance. Ev-
nce is inconclusive regarding the ad-
ion of protein to carbohydrate during
rcise on athletic performance. Seven
dies based on consumption of pre-
rcise meals in addition to carbohy-
te consumption during exercise sug-
t enhanced athletic performance.
idence Grade II�Fair (www.
aevidencelibrary.com/conclusion.cfm?
clusion_statement_id�250453).
overy
e timing and composition of the
st competition or postexercise meal
snack depend on the length and
ensity of the exercise session (eg,
ether glycogen depletion occurred),
d when the next intense workout
ll occur. For example, most athletes ne
March 2009 Volume 109 Number 3
ll finish a marathon with depleted
cogen stores, whereas glycogen
pletion would be less marked fol-
ing a 90-minute training run. Be-
se athletes competing in a mara-
n are not likely to perform another
e or hard workout the same day,
timing and composition of the
stexercise meal is less critical for
se athletes. Conversely, a triath-
e participating in a 90-minute run
the morning and a 3-hour cycling
rkout in the afternoon needs to
ximize recovery between training
sions. The post workout meal as-
mes considerable importance in
eting this goal.
iming of post-exercise carbohy-
te intake affects glycogen synthe-
over the short term (110). Con-
mption of carbohydrates within 30
nutes after exercise (1.0 to 1.5 g
bohydrate/kg at 2-hour intervals
to 6 hours is often recommended)
ults in higher glycogen levels post
rcise than when ingestion is de-
ed for 2 hours (111). It is unneces-
y for athletes who rest one or more
ys between intense training ses-
ns to practice nutrient timing
th regard to glycogen replenish-
nt provided sufficient carbohy-
ates are consumed during the 24-
ur period subsequent to the exercise
t (112). Nevertheless, consuming a
al or snack in close proximity to the
d of exercise may be important for
letes to meet daily carbohydrate
d energy goals.
he type of carbohydrate consumed
o affects post-exercise glycogen syn-
sis. When comparing simple sugars,
cose and sucrose appear equally ef-
tive when consumed at a rate of 1.0
1.5 g/kg body weight for 2 hours;
ctose alone is less effective (113).
th regard to whole foods, consump-
n of carbohydrate with a high glyce-
c index results in higher muscle gly-
en levels 24 hours after glycogen-
leting exercise as compared with
same amount of carbohydrates pro-
ed as foods with a low glycemic in-
(114). Application of these findings
st be considered in conjunction with
athlete’s overall diet. When isoca-
ic amounts of carbohydrates or car-
ydrates plus protein and fat are
vided following endurance (115) or
istance exercise (116), glycogen syn-
sis rates are similar. Including pro-
n in a postexercise