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Physique athletes often incorporate aerobic exercise as part of their exercise program to increase caloric expenditure for the purposes of improving their body composition. One method used by some physique competitors is to perform aerobic exercise in the fasted state under the assumption that low glycogen levels after an overnight fast allow for greater mobilization of stored fat to be used for fuel because carbohydrates are not readily available to produce energy. The purpose of this article is to examine the existing literature on the effect of fasted versus fed cardio on improving body composition for physique athletes.
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Fasted Versus Nonfasted
Aerobic Exercise on Body
Considerations for
Physique Athletes
Guillermo Escalante, DSc, ATC, CSCS, CISSN
and Christopher Barakat, MS, ATC, CSCS, CISSN
California State University San Bernardino, San Bernardino, California; and
Competitive Breed, LLC and The Human
Performance Laboratory, University of Tampa, Tampa, Florida
Physique athletes often incorporate
aerobic exercise as part of their exer-
cise program to increase caloric
expenditure for the purposes of
improving their body composition. One
method used by some physique com-
petitors is to perform aerobic exercise
in the fasted state under the assump-
tion that low glycogen levels after an
overnight fast allow for greater mobili-
zation of stored fat to be used for fuel
because carbohydrates are not readily
available to produce energy. The pur-
pose of this article is to examine the
existing literature on the effect of
fasted versus fed cardio on improving
body composition for physique ath-
Physique athletes compete in vari-
ous divisions within the physique
sport inclusive of bodybuilding,
ness, fitness, and bikini. Although the
levels of muscularity and leanness vary
depending on the division in which an
individual competes in, physique ath-
letes typically aim to lose body fat while
maintaining (or gaining) muscle mass
during their contest preparation period.
To achieve low levels of body fat while
maintaining muscle mass, evidence indi-
cates that competitors typically follow
an 8–16+ week diet in which energy
expenditure increases and caloric intake
decreases (4,8,17,24,31,33,42,49,51).
Because physique competitors resis-
tance train year round with the aim
to maximize muscularity, the increased
caloric expenditure during the contest
preparation phase as a means to
enhance an energy deficit primarily
comes from adding aerobic exercise
into their training regimen. Although
there are many ways in which phy-
sique athletes may perform aerobic
exercise (i.e., type, intensity, duration,
frequency, etc.), performing aerobic
exercise, or “cardio,” as the first thing
in the morning after an overnight fast is
a common strategy used by some com-
petitors (17,25,49). The theory behind
performing fasted cardio is that low
glycogen levels after an overnight fast
allow for greater mobilization of stored
fat to be used for fuel because carbohy-
drates are not readily available to pro-
duce energy. Although in theory this
may seem promising, the purpose of
this article is to examine the existing
literature on the effect of fasted versus
fed cardio on improving body compo-
sition for physique athletes.
Many researchers have examined the
acute effects of fasted and fed aerobic
exercise on carbohydrate and fat
metabolism. In a systematic review
and meta-analysis by Vieira et al. (62),
the authors analyzed 27 studies with
a total of 273 participants and con-
cluded that performing low-intensity
(;40–70% heart rate max) aerobic
exercise in a fasted state induces higher
fat oxidation than exercise performed in
the fed state (62). Many factors have
been demonstrated to impact fuel uti-
lization during exercise (2,62). Some of
these factors include, but are not limited
to, training status, nutritional status (i.e.,
fed versus fasted, macronutrient con-
sumption, etc.), body fat percentage,
exercise type, duration, and intensity
Address correspondence to Guillermo Esca-
fasted aerobic exercise; nonfasted aer-
obic exercise; body composition; fat
loss; physique athletes
Copyright ÓNational Strength and Conditioning Association Strength and Conditioning Journal | 1
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
(5,19,47,54,57,58). Comprehending
how exogenous substrate supply, or the
lack thereof (i.e., fasting), impacts the
acute metabolic responses to exercise
may alter what might be optimal for
physique athletes to implement to
improve body composition.
It is well understood that carbohydrate
consumption before exercise leads to
an increase in blood glucose levels,
and this fuel source (glucose) is effi-
ciently used for muscle contraction,
but also inhibits fat oxidation
(3,13,14,26,30). Conversely, training in
a fasted state has been shown to stim-
ulate the rate of lipolysis and fat oxida-
tion (26,48), partly due to the low levels
of insulin and high levels of epineph-
rine (6). At the cellular level, distinct
differences in metabolism are observed
when comparing fed and fasted condi-
tions due to factors such as gene
expression, acute hormonal changes,
skeletal muscle glycogen content, and
hepatic glycogen content.
Studies have demonstrated that carbo-
hydrate intake significantly inhibits the
exercise-induced changes in mRNA
content that are crucial for fat metabo-
lism, such as fatty acid translocase/
CD36 and carnitine palmitoyltransfer-
ase (11,12). On the contrary, exercising
with low initial glycogen levels (due to
dietary carbohydrate restriction and/or
being in a fasted state) has been shown
to increase basal muscle glycogen con-
tent (23,45,65), mitochondrial oxidative
capacity (28,43), and overall fat-
oxidation rates during low-moderate-
intensity exercise (28,65). Furthermore,
it is well established that during an over-
night fast, glucagon/growth hormone
levels increase, blood glucose/insulin
levels decrease, and energy substrates
are pulled from liver glycogen stores,
which heavily depletes this energy
reserve (44,55). The combination of
the aforementioned acute responses to
fasted aerobic exercise are some of the
reasons that physique athletes rational-
ize using fasted cardio over fed cardio.
Vieira et al. (62) reported that relative
glucose concentrations did not seem to
differ when exercise was performed
fasted versus fed (p50.91). Interest-
ingly, fasted exercise has demonstrated
the ability to increase basal glycogen
content compared to fed exercise. For
example, Van Proeyen et al. (61)
observed a 22% increase in skeletal
muscle basal glycogen content in their
fasted group (p,0.05), whereas no
change occurred in their carbohydrate
fed group (p50.99). Moreover, net
glycogen breakdown during exercise
was similar between the pretest and
posttest for both conditions. Hypothet-
ically, the acute increases in fat oxida-
tion and the effects fasted exercise has
demonstrated regarding the increase in
muscle glycogen are beneficial for
a physique athlete. Because a physique
athlete’s primary concern is body com-
position and aesthetics, these adapta-
tions may translate to a leaner physique
with more muscle fullness over time. In
addition, this increase in basal glycogen
content may improve the physique
athlete’s performance during their
resistance training exercise regimen,
which is crucial for their ability to build
and/or preserve muscle during a caloric
Viera et al. (62) also concluded that the
acute enhancements in fat oxidation
during fasted exercise are derived from
intramyocellular triglycerides (IMCT)
(53,61). Fasted exercise has demon-
strated a reduction in IMCT by
;60% (6,40), whereas fed exercise
was unable to demonstrate any change
in IMCT levels (6). The acute effects on
IMCT that fasted training has demon-
strated seem to be a superior means to
improve insulin sensitivity compared
to exercise in a fed state (60). These
differences may improve carbohydrate
tolerance and may impact how phy-
sique athletes can optimize their nutri-
tional strategies (i.e., carbohydrate
intake) and nutrient timing strategies.
In addition, to the best of the authors’
knowledge, no data exist on how
IMCT levels may impact the visual aes-
thetics of a physique competitor at low
levels of body fat. Perhaps, oxidizing
fatty acids from IMCT and reducing
that storage impacts the muscle’s
appearance (i.e., muscle striations or
separation between muscles (i.e., rectus
femoris, vastus lateralis, medialis, sarto-
rius, etc.). However, it is important to
note that this is purely speculative and
has not been investigated. One impor-
tant confounding variable is the demo-
graphic typically studied (i.e.,
untrained, obese or overweight, or
endurance athletes). Physique athletes
are lean and muscular athletes who are
not generally concerned with their aer-
obic performance capabilities. As pre-
viously mentioned, aerobic exercise is
generally used as one method to
increase their calorie deficit, maximize
fat oxidation, and improve body
In another systematic review and
meta-analysis by Aird et al. (2), the au-
thors analyzed 46 studies to investigate
the effects of fasted versus fed state
exercise on performance and exercise
metabolism. Out of the 46 studies, 45 of
them analyzed postexercise alterations
in various metabolic biomarkers
between the fasted and fed conditions
that are potentially relevant to the ef-
fects of fasted versus fed cardio on
body composition. In regards to the
responses of fasted versus fed cardio
on glucose, free fatty acids, metabolic
hormone signaling, skeletal muscle
metabolism, and adipose tissue metab-
olism, the data are sometimes contra-
dictory. Some variables that seem to
significantly impact these markers are
exercise intensity, duration, subject
demographic (i.e., sedentary, obese/
overweight, aerobic athletic popula-
tion, etc.), meal composition, and tim-
ing in the fed group (2). Aird et al. (2)
noted that metabolic flexibility is a key
variable influencing the body’s ability
to shift from glucose to fat oxidation
during different physiological condi-
tions such as exercising in a fasted or
fed state. Furthermore, it is well under-
stood that the body composition and
lifestyle factors of the subjects signifi-
cantly impact their ability to efficiently
use glucose or oxidize fat (50). Thus,
the findings Aird et al. (2) reported
regarding lack of changes observed in
postexercise blood glucose, insulin, and
free fatty acids in 6 of the 8 studies
Fasted Versus Nonfasted Cardio for Fat Loss
VOLUME 00 | NUMBER 00 | MAY 2020
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
using sedentary and/or overweight/
obese participants may not carry over
to physique athletes.
Collectively, Aird et al. (2) reported
that circulating free fatty acids was
greater during fasted versus fed exer-
cise. These findings suggest that tri-
glyceride mobilization from adipose
tissue is increased during prolonged
fasted aerobic exercise and that these
elevated free fatty acid levels have
potential to be used for fuel (41). Some
evidence has been demonstrated by
Chen et al. (10) regarding the mecha-
nisms that upregulate lipid mobiliza-
tion from adipose tissue in response
to fasted exercise. For example, mRNA
expression of key lipolytic enzymes
such as adipose triglyceride lipase
and hormone-sensitive lipase was up-
regulated only during fasted exercise
(34). Additional evidence regarding
acute hormonal changes have also
favored fasted exercise. For example,
increases in adrenaline, noradrenaline,
and growth hormone were greater in
fasted conditions compared to fed.
Moreover, higher levels of growth hor-
mone have been shown to increase cat-
echolamines (9) which may further
increase fasting-induced lipolysis (16).
When taking all the aforementioned
acute effects of fasted aerobic exercise
into consideration, it is possible that
physique athletes may benefit from this
mode of exercise to improve their body
composition; however, longer training
studies in this population are necessary
to investigate whether significant dif-
ferences are observed between the 2
modes of exercise.
Comprehending the acute effects of
fasted versus fed cardio are important to
help formulate a theoretical construct
that the 2 modes of cardio may have
on body composition; however, acute
changes in exercise metabolism are not
always indicative of improvements in
reducing fat mass. Trabelsi et al. (57)
investigated the effects of body composi-
tion of fed versus fasted state aerobic exer-
cise during Ramadan in physically active
men and concluded that aerobic training
in the fasted state lowered body weight
and body fat percentage; however, fed
aerobic training decreased only body
weight (57). Nineteen males (Fast: n5
10, Fed: n59) performed aerobic training
3 days per week for 40–60 minutes per
session at a heart rate of 60–80% of their
maximum heart rate for 30 days and both
groups lost a significant amount of body
weight (Fast Pre 579.2 63.0kgversus
Fast Po st 77.7 63.0, p,0.01; Fed Pre 5
80.5 kg 64.6 versus Fed Post 578.4 6
4.6, p,0.05), but only the fasted group
lost a significant amount of body fat
percentage (Fast Pre 519.4 61.3%
versus Fast Post 18.6% 61.5%, p,0.05;
Fed P re 519.3% 61.2 versus Fed Post 5
18.8 61.0, p.0.05) (57).
Although these results seem to provide
support for fasted cardio, the results
must be interpreted with caution. First
and foremost, the participant’s diets
were tracked but not controlled; hence,
the absolute daily calorie intake was
significantly higher in the fed group
(3,056 kcal 6183) versus the fasted
group (2,466 kcal 6143) during the
initial 15 days of the study (57). Fur-
thermore, the exercise sessions were
loosely controlled because one partici-
pant was reported to participate in
swimming as part of his exercise ses-
sion, whereas other participants did
one session of rowing, stationary
cycling, and running every week (57).
Moreover, the average length of each
exercise session for the first 15 days of
the intervention to the second 15 days
of the intervention ranged from
46.3 minutes 610.6–46.7 minutes 6
10.7 for the fasted group versus 51.3 mi-
nutes 610.7–49.3 minutes 612.07 for
the fed group (57). Finally, body com-
position was measured using skinfold
calipers (57), which may lead to more
variability in the assessments as
opposed to using Dual X-Ray Absorp-
tiometry or a bioelectrical spectros-
copy device. Collectively, this study
does not provide conclusive evidence
that there is a difference between
fasted and fed cardio with physically
active men when food intake is not
In a systematic review and meta-
analysis on the effect of overnight
fasted exercise on weight loss and
body composition, Hackett and Hag-
strom (21) analyzed 5 studies that
included 96 participants (60 males
and 36 females) aged 21–27 years.
The articles analyzed for this review
included randomized and nonrandom-
ized comparative studies that were
published in English, included healthy
adults, compared exercise after an
overnight fast to exercise in a fed state
using a standardized pre-exercise meal,
and measured body mass and/or body
composition (21). Although the au-
thors stated caution is warranted when
interpreting their findings due to the
limited number of studies available on
the topic, they reported trivial to small
intragroup and intergroup effect sizes
for the effect of fasted versus fed aero-
bic exercise on body mass, % body fat,
and lean mass (21).
Several limitations, some of which were
discussed in the article, should be con-
sidered before generalizing the results
of the review by Hackett and Hagstrom
(21) to physique competitors. First, only
2 (involving females exclusively) of the 5
studies investigated changes in % body
fat and lean mass; thus, it is difficult to
determine the precise effects of fasted
versus fed exercise on fat mass and
fat-free mass, which are critical for
a physique competitor to consider as
opposed to weight loss alone. Second,
because the effect of fasted versus fed
cardio on fat mass and fat-free mass
was only reported in females, their re-
sults cannot be generalized to males.
Furthermore, the dietary interventions
used in the meta-analysis lacked
homogeneity. Only one study in the
meta-analysis, performed by Schoen-
feld et al., provided the participants
with a customized hypocaloric meal
plan that was tracked using a daily on-
line diary and was geared toward
weight loss (52). Hence, out of the 5
studies included in the review article,
only one study’s design would be sim-
ilar and parallel how physique com-
petitors approach their diet when
attempting to lose body fat.
Strength and Conditioning Journal | 3
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Despite the similarities of using a hypo-
caloric diet with aerobic exercise to
lose body fat between physique com-
petitors and the participants in the
Schoenfeld et al. (52) study, many var-
iables remain different. All the partici-
pants in the Schoenfeld et al. study
were females and were prescribed
a daily protein intake of 1.8 g/kg of
body mass along with 60 minutes of
low-moderate steady-state intensity
walking 3 days per week. Moreover,
all aerobic exercise sessions were
supervised and the participants were
instructed not to perform any addi-
tional structured exercise for the dura-
tion of the 4-week study (52). In
addition, the participants in the fasted
and fed exercise groups had baseline
body fat percentages of 26.3 67.9%
and 24.8 68.4%, respectively. In con-
trast to the participants in the Schoen-
feld et al. study (52), physique
competitors are recommended and
have reported to consume more pro-
tein per day (8,17,24,27,42,49), perform
aerobic exercise at various frequencies/
durations/intensities (17,25,42,49), par-
ticipate in a structured resistance train-
ing program (17,25,42,49), and perform
an 8–16+ week intervention to get to
extremely low levels of body fat
(4,8,17,24,31,33,42,49,51). Because
preparation for a competition requires
time, the longer the prep, the more
important “small” changes can com-
pound to yield greater final results.
Furthermore, physique competitors
starting contest preparation generally
begin their fat-loss intervention at rel-
atively low body fat levels; for example,
baseline body fat levels of 10.5–14% for
men and 20.3–22.7% for women have
been reported (27,42,49,56).
Although there are clearly many differ-
ences between physique competitors
and the participants in the study by
Schoenfeld et al. (52), the study was
executed well and is a good compari-
son for the chronic effects of fasted
versus fed cardio that partly represents
a program physique competitors may
follow. Specifically, the results of this
investigation revealed that both the
fasted and fed cardio groups lost
a significant amount of weight and fat
mass over the course of the 4-week
intervention with no statistically signif-
icant between-group differences noted
in body mass, fat mass, or fat-free mass
(52). However, a closer look at the data
because they relate to physique com-
petitors is worth investigating.
The fasted group went from 26.3 6
7.9% body fat to 25.0 67.7% body fat
and from 16.5 65.5 kg to 15.4 65.5 kg
of fat mass, whereas the fed group went
from 24.8 68.4% body fat to 24.1 6
8.5% body fat and from 15.7 66.3kgto
15.0 66.1 kg of fat mass (52). Although
the differences between the 2 groups
did not reach statistical significance, fail-
ing to reach statistical significance does
not always mean it is not practically
relevant. Specifically in the world of
physique competition, the difference
between winning and losing might be
found in small effect sizes that do not
reach statistical significance in research.
In addition, because the individual re-
sults of the participants were not re-
ported in this study, it is not possible
to determine the individual variability
of fat mass and fat-free mass over the
course of the intervention. Furthermore,
this is compounded by limitations of
longitudinal training studies that require
significant time and effort commitments
from the participants. Thus, smaller
sample sizes and shorter intervention
periods are common limitations in
many training studies. Finally, the hor-
monal and metabolic changes that a lean
physique competitor will encounter to
get to extremely low levels of body fat
will be more drastic as they get closer to
competition compared to an individual
who starts a fat loss program at higher
levels of body fat and is only looking to
get to “healthy” levels of body fat (59).
Hence, any minor benefit that may be
derived from fasted cardio should be
considered and further investigated
with physique competitors undergoing
conditions that more closely represent
how they may perform fasted and fed
cardio before definitive conclusions can
be drawn about the effectiveness of the
2 modes of cardio to improve body
Because physique athletes strive for
efficient fat loss and preservation (or
increase) in fat-free mass when prepar-
ing for a competition, the effect of
fasted versus fed cardio exercise on
fat mass and fat-free mass is more
important than weight loss alone. In
one study, investigators reported an
increased nitrogen loss equivalent to
approximately 14 grams of amino
acids per hour during 60 minutes of
fasted cardio (39). Moreover, studies
have shown that consuming food
before exercise increases the thermic
effect of the exercise session, which
leads to greater postexercise energy
expenditure compared to fasted exer-
cise (15,20,35). Evidence suggests that
dietary protein consumed before or
during exercise provides an anticata-
bolic stimulus, which provides a sensi-
ble rationale for exercising individuals
concerned with minimizing protein
breakdown during endurance exercise
(29). Moreover, preliminary research
suggests that consuming a high-
protein meal immediately before exer-
cise may have positive effects on post-
exercise energy expenditure compared
to preexercise carbohydrate intake
(22,64) or fasted conditions (47).
Finally, consuming a high-protein meal
in the morning has demonstrated to
improve feelings of satiety during the
day, decrease continuous snacking,
enhance body composition, and
improve weight loss in conjunction
with a hypocaloric diet (36–38,63).
In a study by Gieke et al. (18), inves-
tigators looked at the effects of various
types of protein feeding before
moderate-intensity exercise in
a fasted-state in 11 college-aged males.
In this randomized, counterbalanced,
crossover investigation, each partici-
pant underwent 4 testing sessions and
was assigned to ingest 1 of the 4 sup-
plementation conditions: 25 g of whey
protein isolate, 25 g casein protein, 25 g
maltodextrin, or a noncaloric control
(18). Using indirect calorimetry, sub-
strate oxidation and resting energy
expenditure were measured at baseline,
Fasted Versus Nonfasted Cardio for Fat Loss
VOLUME 00 | NUMBER 00 | MAY 2020
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
30 minutes later during aerobic exer-
cise performed for 30 minutes at 55–
60% heart rate reserve, and 15 minutes
after exercise (18). The authors re-
ported that postexercise energy expen-
diture was higher with the
consumption of protein compared to
the ingestion of maltodextrin and
tended to be greater than the noncalo-
ric control (18). Furthermore, the
ingestion of protein improved postex-
ercise fat oxidation, whereas no change
was noted in the other groups (18).
Finally, fat oxidation during exercise
increased for all groups but the inges-
tion of casein oxidized significantly
more fat than whey protein
during minutes 10–15 and 25–30 of
the exercise session (18). In closing,
the authors concluded that rates of
energy expenditure and fat oxidation
can be altered after casein consump-
tion before moderate-intensity aerobic
exercise and that fasting did not lead to
increased fat oxidation during or after
exercise (18). Thus, it seems that per-
forming “protein-enhanced cardio”
may offer some benefits to physique
athletes as opposed to performing
fasted cardio or fed cardio that includes
the intake of other nutrients.
The effectiveness of any fat loss inter-
vention is ultimately dictated by creat-
ing a consistent caloric deficit over
time; however, it is important to com-
prehend the complexity of the calories
in versus calories out equation that
seems to be simple at the surface. Dur-
ing periods of prolonged energy
restriction that accompany fat loss,
the body undergoes several metabolic
adaptations aimed at decreasing
energy expenditure, improving meta-
bolic efficiency, and increasing signals
for energy intake that become even
more impactful as a person gets leaner
(60). Simply stated, altering one side of
the energy equation eventually triggers
an inverse response on the other side of
the equation. Hence, despite lowering
energy intake and increasing exercise
time and/or intensity, the body’s abil-
ity to lose more body fat becomes
exponentially more challenging.
Because physique competitors must
reach unusually low levels of body fat
to succeed in their sport, fat loss pla-
teaus are often encountered that are
difficult to overcome. Some of these
plateaus may not be significant for
the average person attempting to lose
a few pounds of body fat; however,
physique competitors with a desire to
win must overcome these obstacles if
they are to succeed at maximizing their
improvements in body composition.
Although no conclusive evidence ex-
ists on the superiority of fasted versus
fed cardio to improve body composi-
tion, research on physique competitors
has not been performed, to the best of
the authors’ knowledge. Because criti-
cal differences such as starting body fat
levels, protein intake, resistance train-
ing programming, and cardio exercise
prescription exist between physique
competitors and other populations,
the effects of fasted versus fed cardio
on other populations may not carry
over to physique competitors. Further-
more, subtle changes in body compo-
sition that may be irrelevant to those in
other populations may be the differ-
ence between winning and losing
a physique competition. Moreover,
physique competitors commonly use
thermogenic supplements (i.e., caf-
feine, yohimbine, etc.) before cardio
that have been shown to increase the
acute fat oxidation effects (1,7,32,46),
with some data demonstrating these
acute changes resulted in significant
reductions in fat mass and body fat
percentage over a 21-day period (46).
Although further discussion of this
topic is beyond the scope of this article,
it is something that should be consid-
ered because ingesting these supple-
ments may alter how the body
responds to fasted versus fed cardio.
Until longer-lasting investigations on
the effects of fasted versus fed versus
protein-enhanced cardio on body
composition are performed on phy-
sique competitors, it is not possible to
determine which mode of cardio (if
any) is more beneficial than the other
for this population. As stated previ-
ously, in a meta-analysis on the acute
effects of fasted and fed aerobic exer-
cise on carbohydrate and fat metabo-
lism, the authors concluded that
performing aerobic exercise in a fasted
state induces more fat oxidation than
exercise performed in the fed state
(11). Chronic fasted-state cardio train-
ing has also been shown to improve
glucose tolerance and insulin sensitivity
during an energy restricted high-fat
diet compared to the same training
conducted after feeding (61). More-
over, performing fasted cardio has been
shown to upregulate maximal rates of
oxidative enzyme activity, impede in-
traexercise glycogen breakdown, and
increase rates of peripheral and intra-
myocellular fat oxidation. However,
because fasted cardio may promote
protein degradation in prolonged
exhaustive sessions, ingesting protein
before cardio may offer a benefit to
physique competitors whose goal is
to lose body fat and maintain (or gain)
fat-free mass in the process even if their
cardio sessions are typically of lower
intensity and duration. Preliminary
data also suggest that protein-
enhanced cardio increases postexercise
energy expenditure and improves post-
exercise fat oxidation.
Based on the current available evi-
dence, the following practical applica-
tions may be advisable for physique
competitors and coaches:
Physique athletes may use fasted,
fed, or protein-enhanced cardio as
their primary aerobic exercise mode
to increase their caloric expenditure,
increase their overall deficit, and
improve their body composition.
Protein-enhanced cardio may mini-
mize losses of fat-free mass by pro-
viding an anticatabolic stimulus.
Furthermore, protein-enhanced
cardio may increase postexercise
energy expenditure and improve
postexercise fat oxidation as
opposed to fed or fasted cardio.
Fasted exercise can be performed at
various intensities. However, it is not
suggested to perform fasted exercise
for more than 60 minutes due to
potential losses of fat-free mass from
Strength and Conditioning Journal | 5
Copyright © National Strength and Conditioning Association. Unauthorized reproduction of this article is prohibited.
lack of carbohydrates with pro-
longed activity. Furthermore,
because high-intensity exercise relies
primarily on carbohydrates as
a source of ATP production, lower-
intensity exercise may be more
favorable for caloric expenditure so
as to prevent the breakdown of pro-
teins to make glucose through
Because improving aerobic perfor-
mance is not a primary goal for phy-
sique athletes, the cardio intensity
and modality used should ideally
improve recovery from resistance
training, minimize systemic fatigue
accumulation, and maximize adher-
ence. Thus, it is important that phy-
sique athletes perform cardio at an
appropriate frequency, intensity,
duration, and mode (i.e., cycling,
stairmaster, walking, etc.) that best
complements the rest of their train-
ing demands and lifestyle
Conflicts of Interest and Source of Funding:
The authors report no conflicts of interest
and no source of funding.
Escalante is an
associate professor
of Kinesiology at
California State
University San
Barakat is owner
and coach at the
Competitive Breed,
LLC, and Adjunct
Instructor of
Human Perfor-
mance at the Uni-
versity of Tampa.
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Fasted Versus Nonfasted Cardio for Fat Loss
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... In terms of aesthetics, current research shows that fasting can be used when performing low-intensity endurance training to improve body composition. However, it is not recommended to perform fasted exercise for bouts lasting more than 60 minutes or when performing high-intensity exercise (Guillermo & Barakat, 2020). This is because being in a fasted state while performing long duration or high-intensity exercise can result in a catabolic state where the body is forced to break down muscle tissue in order to produce and provide available energy. ...
... This made it difficult to report detailed training routine information. Additionally, Escalante and Barakat [31] reviewed fasted versus nonfasted aerobic exercise on body composition for physique athletes, and stated the difficult to discuss the real effects of fasted versus nonfasted aerobic exercise due to methodological aspects (i.e., controlled studies). In this sense, the hypothesis of low glycogen levels after an overnight fast allowing greater stored fat mobilization to be used for fuel remains inconclusive. ...
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Bodybuilding is a sport that requires adequate training strategies in order to maximize skeletal muscle hypertrophy. The purpose of the present review was to perform a narrative assessment of the training routines designed for muscle hypertrophy used by bodybuilders. A search was carried out in the databases Pubmed/MEDLINE, Scielo, EBSCO, LILACS, SportDiscus, Web of Science, and CINAHL with the words "Resistance training" and "hypertrophy" in bodybuilders and their variations that involve the respective outcomes. Fourteen studies were identified that investigated the long-term training routines of bodybuilders. These studies demonstrate a pattern in the training organization, whereby there is a separation of training into four distinct periods: off-season, pre-contest, peak week, and post-contest. Each period has a specific spectrum of intensity load, total training volume, and exercise type (multi-or single-joint). We conclude that bodybuilding competitors employed a higher intensity load, lower number of repetitions, and longer rest intervals in the off-season than pre-contest.
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Nutrition and exercise metabolism are vibrant physiological fields, yet at times it feels as if greater progress could be made by better integrating these disciplines. Exercise is advocated for improving metabolic health, in part by increasing peripheral insulin sensitivity and glycaemic control. However, when a modest-to-high carbohydrate load is consumed before and/or during each exercise bout within a training programme, increases in oral glucose insulin sensitivity can be blunted in both men of a healthy weight and those with overweight/obesity. Exercise training-induced adaptation in the energy sensing AMP-activated protein kinase (AMPK) and the insulin-sensitive glucose transporter GLUT4 protein levels are sensitive to pre-exercise feeding status in both healthy individuals and individuals classified as overweight or obese. Increased lipid oxidation may, in part, explain the enhanced adaptive responses to exercise training performed before (i.e. fasted-state exercise) versus after nutrient ingestion. Evidence in individuals with type 2 diabetes currently shows no effect of altering nutrient-exercise timing for measured markers of metabolic health, or greater reductions in glycated haemoglobin (HbA1c) concentrations with exercise performed after versus before nutrient provision. Since the metabolic inflexibility associated with type 2 diabetes diminishes differences in lipid oxidation between the fasted and fed states, it is plausible that pre-exercise feeding status does not alter adaptations to exercise when metabolic flexibility is already compromised. Current evidence suggests restricting carbohydrate intake before and during exercise can enhance some health benefits of exercise, but in order to establish clinical guidelines, further research is needed with hard outcomes and different populations.
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Background Augmenting fat oxidation is a primary goal of fitness enthusiasts and individuals desiring to improve their body composition. Performing aerobic exercise while fasted continues to be a popular strategy to achieve this outcome, yet little research has examined how nutritional manipulations influence energy expenditure and/or fat oxidation during and after exercise. Initial research has indicated that pre-exercise protein feeding may facilitate fat oxidation while minimizing protein degradation during exercise, but more research is needed to determine if the source of protein further influences such outcomes. Methods Eleven healthy, college-aged males (23.5 ± 2.1 years, 86.0 ± 15.6 kg, 184 ± 10.3 cm, 19.7 ± 4.4%fat) completed four testing sessions in a randomized, counter-balanced, crossover fashion after observing an 8–10 h fast. During each visit, baseline substrate oxidation and resting energy expenditure (REE) were assessed via indirect calorimetry. Participants ingested isovolumetric, solutions containing 25 g of whey protein isolate (WPI), 25 g of casein protein (CAS), 25 g of maltodextrin (MAL), or non-caloric control (CON). After 30 min, participants performed 30 min of treadmill exercise at 55–60% heart rate reserve. Substrate oxidation and energy expenditure were re-assessed during exercise and 15 min after exercise. Results Delta scores comparing the change in REE were normalized to body mass and a significant group x time interaction (p = 0.002) was found. Post-hoc comparisons indicated the within-group changes in REE following consumption of WPI (3.41 ± 1.63 kcal/kg) and CAS (3.39 ± 0.82 kcal/kg) were significantly greater (p < 0.05) than following consumption of MAL (1.57 ± 0.99 kcal/kg) and tended to be greater than the non-caloric control group (2.00 ± 1.91 kcal/kg, p = 0.055 vs. WPI and p = 0.061 vs. CAS). Respiratory exchange ratio following consumption of WPI and CAS significantly decreased during the post exercise period while no change was observed for the other groups. Fat oxidation during exercise was calculated and increased in all groups throughout exercise. CAS was found to oxidize significantly more fat (p < 0.05) than WPI during minutes 10–15 (CAS: 2.28 ± 0.38 g; WPI: 1.7 ± 0.60 g) and 25–30 (CAS: 3.03 ± 0.55 g; WPI: 2.24 ± 0.50 g) of the exercise bout. Conclusions Protein consumption before fasted moderate-intensity treadmill exercise significantly increased post-exercise energy expenditure compared to maltodextrin ingestion and tended to be greater than control. Post-exercise fat oxidation was improved following protein ingestion. Throughout exercise, fasting (control) did not yield more fat oxidation versus carbohydrate or protein, while casein protein allowed for more fat oxidation than whey. These results indicate rates of energy expenditure and fat oxidation can be modulated after CAS protein consumption prior to moderate-intensity cardiovascular exercise and that fasting did not lead to more fat oxidation during or after exercise.
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Background Competitive bodybuilders employ a combination of resistance training, cardiovascular exercise, calorie reduction, supplementation regimes and peaking strategies in order to lose fat mass and maintain fat free mass. Although recommendations exist for contest preparation, applied research is limited and data on the contest preparation regimes of bodybuilders are restricted to case studies or small cohorts. Moreover, the influence of different nutritional strategies on competitive outcome is unknown. Methods Fifty-one competitors (35 male and 16 female) volunteered to take part in this project. The British Natural Bodybuilding Federation (BNBF) runs an annual national competition for high level bodybuilders; competitors must qualify by winning at a qualifying events or may be invited at the judge’s discretion. Competitors are subject to stringent drug testing and have to undergo a polygraph test. Study of this cohort provides an opportunity to examine the dietary practices of high level natural bodybuilders. We report the results of a cross-sectional study of bodybuilders competing at the BNBF finals. Volunteers completed a 34-item questionnaire assessing diet at three time points. At each time point participants recorded food intake over a 24-h period in grams and/or portions. Competitors were categorised according to contest placing. A “placed” competitor finished in the top 5, and a “Non-placed” (DNP) competitor finished outside the top 5. Nutrient analysis was performed using Nutritics software. Repeated measures ANOVA and effect sizes (Cohen’s d) were used to test if nutrient intake changed over time and if placing was associated with intake. ResultsMean preparation time for a competitor was 22 ± 9 weeks. Nutrient intake of bodybuilders reflected a high-protein, high-carbohydrate, low-fat diet. Total carbohydrate, protein and fat intakes decreased over time in both male and female cohorts (P < 0.05). Placed male competitors had a greater carbohydrate intake at the start of contest preparation (5.1 vs 3.7 g/kg BW) than DNP competitors (d = 1.02, 95% CI [0.22, 1.80]). Conclusions Greater carbohydrate intake in the placed competitors could theoretically have contributed towards greater maintenance of muscle mass during competition preparation compared to DNP competitors. These findings require corroboration, but will likely be of interest to bodybuilders and coaches.
Full-text available
The effects of carbohydrate or water ingestion on metabolism were investigated in seven male subjects during two running and two cycling trials lasting 60 min at individual lactate threshold using indirect calorimetry, U- ¹⁴ C-labeled tracer-derived measures of the rates of oxidation of plasma glucose, and direct determination of mixed muscle glycogen content from the vastus lateralis before and after exercise. Subjects ingested 8 ml/kg body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or water 10 min before exercise and an additional 2 ml/kg body mass of the same fluid after 20 and 40 min of exercise. Plasma glucose oxidation was greater with CHO than with water during both running (65 ± 20 vs. 42 ± 16 g/h; P < 0.01) and cycling (57 ± 16 vs. 35 ± 12 g/h; P < 0.01). Accordingly, the contribution from plasma glucose oxidation to total carbohydrate oxidation was greater during both running (33 ± 4 vs. 23 ± 3%; P < 0.01) and cycling (36 ± 5 vs. 22 ± 3%; P < 0.01) with CHO ingestion. However, muscle glycogen utilization was not reduced by the ingestion of CHO compared with water during either running (112 ± 32 vs. 141 ± 34 mmol/kg dry mass) or cycling (227 ± 36 vs. 216 ± 39 mmol/kg dry mass). We conclude that, compared with water, 1) the ingestion of carbohydrate during running and cycling enhanced the contribution of plasma glucose oxidation to total carbohydrate oxidation but 2) did not attenuate mixed muscle glycogen utilization during 1 h of continuous submaximal exercise at individual lactate threshold.
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This study determined if the suppression of lipolysis after preexercise carbohydrate ingestion reduces fat oxidation during exercise. Six healthy, active men cycled 60 min at 44 ± 2% peak oxygen consumption, exactly 1 h after ingesting 0.8 g/kg of glucose (Glc) or fructose (Fru) or after an overnight fast (Fast). The mean plasma insulin concentration during the 50 min before exercise was different among Fast, Fru, and Glc (8 ± 1, 17 ± 1, and 38 ± 5 μU/ml, respectively; P< 0.05). After 25 min of exercise, whole body lipolysis was 6.9 ± 0.2, 4.3 ± 0.3, and 3.2 ± 0.5 μmol ⋅ kg-1⋅ min-1and fat oxidation was 6.1 ± 0.2, 4.2 ± 0.5, and 3.1 ± 0.3 μmol ⋅ kg-1⋅ min-1during Fast, Fru, and Glc, respectively (all P < 0.05). During Fast, fat oxidation was less than lipolysis ( P < 0.05), whereas fat oxidation approximately equaled lipolysis during Fru and Glc. In an additional trial, the same subjects ingested glucose (0.8 g/kg) 1 h before exercise and lipolysis was simultaneously increased by infusing Intralipid and heparin throughout the resting and exercise periods (Glc+Lipid). This elevation of lipolysis during Glc+Lipid increased fat oxidation 30% above Glc (4.0 ± 0.4 vs. 3.1 ± 0.3 μmol ⋅ kg-1⋅ min-1; P < 0.05), confirming that lipolysis limited fat oxidation. In summary, small elevations in plasma insulin before exercise suppressed lipolysis during exercise to the point at which it equaled and appeared to limit fat oxidation.
Full-text available
It remains unclear whether training in fasted compared to fed states leads to greater weight loss and whether this practice results in beneficial or detrimental changes in body composition. We conducted a systematic review to examine the effect of overnight-fasted versus fed exercise on weight loss and body composition. Seven electronic databases were searched using terms related to fasting and exercise. Inclusion criteria were: randomised and non-randomised comparative studies; published in English; included healthy adults; compared exercise following an overnight fast to exercise in a fed state; used a standardized pre-exercise meal for the fed condition; and measured body mass and/or body composition. A total of five studies were included involving 96 participants. Intra-group analysis for the effect of fasted and fed aerobic exercise revealed trivial to small effect sizes on body mass. The inter-group effect for the interventions on body mass was trivial. Intra-group effects were small for % body fat and trivial for lean mass in females, with trivial effects also found for the inter-groups analyses. Whilst this is the first systematic review and meta-analysis to investigate this topic, caution is warranted when interpreting the findings due to the limited number of studies and hence insufficient data.
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Position statement The International Society of Sports Nutrition (ISSN) provides an objective and critical review related to the intake of protein for healthy, exercising individuals. Based on the current available literature, the position of the Society is as follows: 1) An acute exercise stimulus, particularly resistance exercise, and protein ingestion both stimulate muscle protein synthesis (MPS) and are synergistic when protein consumption occurs before or after resistance exercise. 2) For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day (g/kg/d) is sufficient for most exercising individuals, a value that falls in line within the Acceptable Macronutrient Distribution Range published by the Institute of Medicine for protein. 3) There is novel evidence that suggests higher protein intakes (>3.0 g/kg/d) may have positive effects on body composition in resistance-trained individuals (i.e., promote loss of fat mass). 4) Recommendations regarding the optimal protein intake per serving for athletes to maximize MPS are mixed and are dependent upon age and recent resistance exercise stimuli. General recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g. 5) Acute protein doses should strive to contain 700–3000 mg of leucine and/or a higher relative leucine content, in addition to a balanced array of the essential amino acids (EAAs). 6) These protein doses should ideally be evenly distributed, every 3–4 h, across the day. 7) The optimal time period during which to ingest protein is likely a matter of individual tolerance, since benefits are derived from pre- or post-workout ingestion; however, the anabolic effect of exercise is long-lasting (at least 24 h), but likely diminishes with increasing time post-exercise. 8) While it is possible for physically active individuals to obtain their daily protein requirements through the consumption of whole foods, supplementation is a practical way of ensuring intake of adequate protein quality and quantity, while minimizing caloric intake, particularly for athletes who typically complete high volumes of training. 9) Rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating MPS. 10) Different types and quality of protein can affect amino acid bioavailability following protein supplementation. 11) Athletes should consider focusing on whole food sources of protein that contain all of the EAAs (i.e., it is the EAAs that are required to stimulate MPS). 12) Endurance athletes should focus on achieving adequate carbohydrate intake to promote optimal performance; the addition of protein may help to offset muscle damage and promote recovery. 13) Pre-sleep casein protein intake (30–40 g) provides increases in overnight MPS and metabolic rate without influencing lipolysis.
Tinsley, GM, Trexler, ET, Smith-Ryan, AE, Paoli, A, Graybeal, AJ, Campbell, BI, and Schoenfeld, BJ. Changes in body composition and neuromuscular performance through preparation, two competitions, and a recovery period in an experienced female physique athlete. J Strength Cond Res XX(X): 000-000, 2018-This prospective case study evaluated an experienced female figure competitor during contest preparation, 2 competitions, and a recovery period. Twelve laboratory sessions were conducted over 8 months. At each visit, body composition was assessed by 4-compartment model, resting metabolic rate (RMR) by indirect calorimetry, and neuromuscular performance by peak force and rate of force development (RFD) on a mechanized squat device. Caloric intake ranged from 965 to 1,610 kcal·d (16.1-24.8 kcal·kg·BM; 18.2-31.1 kcal·kg·FFM), with varying macronutrient intakes (CHO: 0.3-4.8 g·kg; PRO: 1.7-3.0 g·kg; and FAT: 0.2-0.5 g·kg). Body fat was reduced from 20.3 to 12.2% before the first competition and declined to 11.6% before the second competition. Fat-free mass increased by 2.1% before the first competition and peaked at 4.6% above baseline in the recovery period. Resting metabolic rate decreased from 1,345 kcal·d at baseline to a low value of 1,119 kcal·d between competitions. By the end of recovery, RMR increased to 1,435 kcal·d. Concentric and eccentric peak forces declined by up to 19% before the first competition, experienced perturbations in the inter-competition and recovery periods, and remained 5-8% below baseline at study termination. Similarly, RFD decreased by up to 57% before the first competition, was partially recovered, but remained 39% lower than baseline at study termination. Despite favorable body composition changes, neuromuscular performance was impaired during and after the competitive season in an experienced female physique competitor.
This study aimed to describe the body composition and physiological changes which take place during the in-season and recovery periods of a group of natural bodybuilders. Natural male bodybuilders (n = 9) were assessed 16 (PRE16), 8 (PRE8), and 1 (PRE1) week(s) before, and 4 (POST4) weeks after a bodybuilding competition. Assessments included body composition, resting metabolic rate (RMR), serum hormones, and 7-day weighed food and training diaries. Change in parameters was assessed using repeated-measures analysis of variance. Dietary protein intake remained high throughout the study period (2.8–3.1 g kg⁻¹ d⁻¹). Fat mass (FM) was significantly reduced from PRE16 to PRE1 (8.8 ± 3.1 vs. 5.3 ± 2.4 kg, P < .01). There was a small decrease in lean mass (LM) from PRE8 to PRE1 (71.8 ± 9.1 vs. 70.9 ± 9.1 kg, P < .05). No changes in RMR were observed (P > .05). Large reductions in total and free testosterone (16.4 ± 4.4 vs. 10.1 ± 3.6 nmol L⁻¹, P < .05; 229.3 ± 72.4 vs. 116.8 ± 76.9 pmol L⁻¹, P < .05), and insulin-like growth factor-1 (IGF-1) (27.0 ± 7.7 vs. 19.9 ± 7.6 nmol L⁻¹, P < .05) occurred between PRE16 and PRE1. LM and IGF-1 increased from PRE1 to POST4 (70.9 ± 9.1 vs. 72.5 ± 8.5 kg, P < .05; 19.9 ± 7.6 vs. 25.4 ± 9.3 nmol L⁻¹, P < .05). Despite substantial reductions in FM, participants maintained almost all of their LM. The reduction in anabolic hormone concentration is likely attributable to the prolonged negative energy balance, despite a high dietary protein intake.