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Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training

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Is an Energy Surplus Required to Maximize Skeletal Muscle Hypertrophy Associated With Resistance Training

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Resistance training is commonly prescribed to enhance strength/power qualities and is achieved via improved neuromuscular recruitment, fiber type transition, and/ or skeletal muscle hypertrophy. The rate and amount of muscle hypertrophy associated with resistance training is influenced by a wide array of variables including the training program, plus training experience, gender, genetic predisposition, and nutritional status of the individual. Various dietary interventions have been proposed to influence muscle hypertrophy, including manipulation of protein intake, specific supplement prescription, and creation of an energy surplus. While recent research has provided significant insight into optimization of dietary protein intake and application of evidence based supplements, the specific energy surplus required to facilitate muscle hypertrophy is unknown. However, there is clear evidence of an anabolic stimulus possible from an energy surplus, even independent of resistance training. Common textbook recommendations are often based solely on the assumed energy stored within the tissue being assimilated. Unfortunately, such guidance likely fails to account for other energetically expensive processes associated with muscle hypertrophy, the acute metabolic adjustments that occur in response to an energy surplus, or individual nuances like training experience and energy status of the individual. Given the ambiguous nature of these calculations, it is not surprising to see broad ranging guidance on energy needs. These estimates have never been validated in a resistance training population to confirm the “sweet spot” for an energy surplus that facilitates optimal rates of muscle gain relative to fat mass. This review not only addresses the influence of an energy surplus on resistance training outcomes, but also explores other pertinent issues, including “how much should energy intake be increased,” “where should this extra energy come from,” and “when should this extra energy be consumed.” Several gaps in the literature are identified, with the hope this will stimulate further research interest in this area. Having a broader appreciation of these issues will assist practitioners in the establishment of dietary strategies that facilitate resistance training adaptations while also addressing other important nutrition related issues such as optimization of fuelling and recovery goals. Practical issues like the management of satiety when attempting to increase energy intake are also addressed.
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REVIEW
published: 20 August 2019
doi: 10.3389/fnut.2019.00131
Frontiers in Nutrition | www.frontiersin.org 1August 2019 | Volume 6 | Article 131
Edited by:
Andrew Philp,
Garvan Institute of Medical
Research, Australia
Reviewed by:
Nicholas A. Burd,
University of Illinois at
Urbana-Champaign, United States
Scott Forbes,
Brandon University, Canada
*Correspondence:
Gary John Slater
gslater@usc.edu.au
Specialty section:
This article was submitted to
Sport and Exercise Nutrition,
a section of the journal
Frontiers in Nutrition
Received: 08 April 2019
Accepted: 02 August 2019
Published: 20 August 2019
Citation:
Slater GJ, Dieter BP, Marsh DJ,
Helms ER, Shaw G and Iraki J (2019)
Is an Energy Surplus Required to
Maximize Skeletal Muscle Hypertrophy
Associated With Resistance Training.
Front. Nutr. 6:131.
doi: 10.3389/fnut.2019.00131
Is an Energy Surplus Required to
Maximize Skeletal Muscle
Hypertrophy Associated With
Resistance Training
Gary John Slater 1,2
*, Brad P. Dieter 3, Damian James Marsh4, Eric Russell Helms 5,
Gregory Shaw 6and Juma Iraki 7
1School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore, QLD, Australia, 2Australian Institute
of Sport, Canberra, ACT, Australia, 3Department of Pharmaceutical Sciences, Washington State University, WA Spokane,
WA, United States, 4Fiji Rugby Union, Suva, Fiji, 5Auckland University of Technology, Sports Performance Research Institute
New Zealand, Auckland, New Zealand, 6Swimming Australia, Brisbane, QLD, Australia, 7Iraki Nutrition AS, Fjerdingby,
Norway
Resistance training is commonly prescribed to enhance strength/power qualities and
is achieved via improved neuromuscular recruitment, fiber type transition, and/ or
skeletal muscle hypertrophy. The rate and amount of muscle hypertrophy associated
with resistance training is influenced by a wide array of variables including the training
program, plus training experience, gender, genetic predisposition, and nutritional status
of the individual. Various dietary interventions have been proposed to influence muscle
hypertrophy, including manipulation of protein intake, specific supplement prescription,
and creation of an energy surplus. While recent research has provided significant
insight into optimization of dietary protein intake and application of evidence based
supplements, the specific energy surplus required to facilitate muscle hypertrophy
is unknown. However, there is clear evidence of an anabolic stimulus possible
from an energy surplus, even independent of resistance training. Common textbook
recommendations are often based solely on the assumed energy stored within the
tissue being assimilated. Unfortunately, such guidance likely fails to account for other
energetically expensive processes associated with muscle hypertrophy, the acute
metabolic adjustments that occur in response to an energy surplus, or individual nuances
like training experience and energy status of the individual. Given the ambiguous nature
of these calculations, it is not surprising to see broad ranging guidance on energy needs.
These estimates have never been validated in a resistance training population to confirm
the “sweet spot” for an energy surplus that facilitates optimal rates of muscle gain
relative to fat mass. This review not only addresses the influence of an energy surplus
on resistance training outcomes, but also explores other pertinent issues, including “how
much should energy intake be increased,” “where should this extra energy come from,”
and “when should this extra energy be consumed.” Several gaps in the literature are
identified, with the hope this will stimulate further research interest in this area. Having
a broader appreciation of these issues will assist practitioners in the establishment of
Slater et al. Energy Surplus and Resistance Training
dietary strategies that facilitate resistance training adaptations while also addressing
other important nutrition related issues such as optimization of fuelling and recovery
goals. Practical issues like the management of satiety when attempting to increase
energy intake are also addressed.
Keywords: muscle hypertrophy, sports nutrition, resistance exercise, diet, nutrient timing
INTRODUCTION
Resistance training is commonly prescribed to increase
underlying strength and power qualities in an attempt to
improve athletic performance. The enhancement of these
qualities may be derived from a range of potential adaptations
including improved neuromuscular recruitment, fiber type
transition, and/ or skeletal muscle hypertrophy. Promoting
hypertrophy is especially important in strength sports, given the
strong relationship between fat free mass (FFM) and competitive
lifting performance (1,2). Furthermore, in contact sports such
as rugby union, larger players have a clear advantage (3) which
is highlighted in World Cup data where total mass of forwards
is correlated with success (4,5). Amongst elite youth rugby
league players, quadriceps muscle hypertrophy is related to
enhancement of running speed (6). However, this may not be
appropriate for all athletes with skeletal muscle hypertrophy
possibly resulting in adverse adaptations, including a transition
away from fast twitch glycolytic fibers and slower contraction
velocity characteristics (7) if inappropriately prescribed. Thus,
unless the increase in power proportionally exceeds any
associated weight gain, performance is unlikely to be enhanced
by skeletal muscle hypertrophy. Collectively there is support for
the potential of skeletal muscle hypertrophy enhancing athletic
performance, but individual athlete nuances must be considered
by coaching personnel and training prescribed so as to facilitate
adaptations in both muscle hypertrophy and power so that
any associated increase in body mass does not negatively affect
variables like speed (8).
The manipulation of dietary intake is common among
individuals attempting to facilitate resistance training gains in
strength and skeletal muscle hypertrophy. Aside from water
(75%), skeletal muscle is made up of protein (20%), with
the remainder from other materials including fat, glycogen,
inorganic salts, and minerals (9). Given the protein content of
skeletal muscle, it is perhaps not surprising resistance trained
athletes emphasize the importance of dietary protein in their
meal plans (10). This is also reflected in the scientific literature
with significant attention given to protein focused nutritional
interventions to facilitate resistance training induced adaptations
(11), including manipulation of total daily dietary protein intake
(12), protein dosage per meal (1315), protein quality (16),
and protein distribution (17). While a recent meta-analysis
suggested dietary protein supplementation enhances resistance
training induced gains in muscle mass and strength, at least
when dietary protein intake is suboptimal (<1.6 g·kg1daily)
(18), resistance training alone provides a far greater stimulus
than protein supplementation (14). Given this, a number of other
dietary strategies have previously been proposed to augment
the resistance training response, including the creation of a
positive energy balance (19,20). While facilitating a positive
energy balance is not supported by others because of the
potential for increments in fat mass (FM) (21), there is clear
evidence of a whole body anabolic response to overfeeding, even
in the absence of a resistance training stimulus in sedentary
populations (22,23). This raises a question about composition
of the lean mass accretion in this scenario i.e., skeletal muscle
vs. splanchnic protein (24), especially given the lack of change
in mammalian target of rapamycin (mTOR) (25). Furthermore,
additional energy does not appear to further modulate the acute
muscle protein synthesis (MPS) response to dietary protein
ingestion at rest (26), or following resistance exercise (27,28).
Despite this, numerous textbooks used in the training of nutrition
professionals advocate the creation of an energy surplus when
attempting to facilitate skeletal muscle hypertrophy (2932).
The exact energy cost of skeletal muscle hypertrophy is not
known. Likewise, it is not clear if this energy cost can be
met purely from endogenous (i.e., internal fat stores) and/or
exogenous sources (i.e., diet). Indeed, there is clear evidence
of marked skeletal muscle hypertrophy in response to a novel
resistance training stimulus in otherwise healthy, overweight
individuals in conjunction with a hypoenergetic, higher protein
meal plan (33,34). While similar concurrent reductions in FM
and gains in FFM have been observed in elite and professional
athletes following return to sport after an off-season break (35)
or injury (36,37), this response is less evident in highly trained
individuals exposed regularly to a resistance training stimulus
(38). This raises the possibility that individual nuances may
need to be considered, including energy status and training
history. Indeed, there is research confirming initial body fat stores
influence metabolic response to starvation (39), while individuals
with higher FFM and cardiorespiratory fitness gain less FM
relative to FFM during isoenergetic, isonitrogenous overfeeding
in a sedentary state (40). Preliminary research indicates younger
athletes experience more pronounced physique and physical
characteristic training adaptations compared to their older peers
(41), a trend also even amongst mature professional athletes
(38). A better appreciation of these individual nuances may
assist with establishing realistic training adaptation aspirations,
plus prescription of training and diet interventions to facilitate
skeletal muscle hypertrophy.
It is not known if any adjustment in dietary intake to
support muscle hypertrophy is required to merely contribute the
building blocks of skeletal muscle while also accounting for the
metabolic cost of generating new skeletal muscle mass (SMM),
or if the physiological response to an energy surplus amplifies
the anabolic signal created by resistance training. Addressing
these fundamental questions is paramount to future prescription
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Slater et al. Energy Surplus and Resistance Training
of energy intake guidance associated with dietary strategies
to optimize skeletal muscle hypertrophy. Given the dearth of
research specifically examining the influence of an energy surplus
on resistance training outcomes, an exploration of overfeeding
studies independent of resistance exercise has also been included
in this review. This needs to be considered, given the impact of
resistance training on sensitivity to nutrition support. Indeed, a
single resistance training session can serve to potentiate MPS in
response to protein feeding (42), an effect which may persist for
upwards of 24–48 h after resistance exercise (43,44).
Overfeeding alone is not sufficient to produce favorable body
composition changes such that proportionally more FFM is
gained than FM. Indeed, while 100 days of energy surplus
(totaling 353 MJ) among young lean males resulted in significant
individual variation in body composition change, 2 kg of FM
were accrued for each 1 kg of lean mass (45). In Leaf and
Antonio’s summary of overfeeding studies, they also note that
predominantly more FM is gained with overfeeding in the
absence of resistance training (46). However, it seems unlikely
that overfeeding alone would produce meaningful increases in
contractile tissue as the initiating event which induces skeletal
muscle hypertrophy after maturation is the production of
sufficient tension (47) and subsequent mechanotransduction at
the muscle fiber level (48). In an exercise or strength and
conditioning setting, this stimulus is supplied via progressive
resistance training. Other related factors such as the resultant
muscle damage, metabolic fatigue, and hormonal response
to resistance training are speculated to either correlate with,
be additive to, or play a permissive role in training-induced
hypertrophy, but are not yet fully understood (49). It is plausible
that nutrition could influence some of these factors.
This review not only addresses the impact of energy balance
on resistance training outcomes, with an emphasis on skeletal
muscle hypertrophy, but also explores other important issues,
including “how big should the energy surplus be,” “where
should the extra energy come from,” and “when should this
extra energy be consumed.” Having a broader understanding of
these issues will help establish nutrition strategies to optimize
resistance training adaptations and at the same time address
nutritional issues such as optimizing recovery and fuelling goals.
A broader understanding of the physiological implications of an
energy surplus not only has clear application to the resistance
trained athlete but may also be applicable to clinical populations
where retention or promotion of SMM may be advantageous.
While it is recognized supplement use is common amongst
resistance trained athletes (50), and there is empirical evidence
to support the use of supplements like creatine monohydrate in
facilitating resistance training adaptations (51), the focus of this
review remains with exploring the impact of energy balance on
resistance training outcomes.
ENERGY BALANCE
The daily energy cost of protein turnover accounts for 20%
of resting energy needs or 18 kJ·kg1body mass (52). Skeletal
muscle hypertrophy requires the further remodeling of muscle,
ensuring it is an energy intensive process. As such, there has been
much discussion around the role of energy balance (i.e., energy
surpluses, energy deficits, and isocaloric states) in modulating
hypertrophy. Currently, there is a paucity of literature that
directly addresses the precise role energy deficits, surpluses, and
net balance states play in muscle hypertrophy.
Only a few studies have directly assessed the role of energy
balance on skeletal muscle hypertrophy in response to resistance
training and these focus specifically on the impact of an energy
deficit. Indeed, an acute, moderate energy deficit (80% of
estimated energy requirements) that promoted 1.0 kg weight
loss over 10 days amongst young healthy volunteers resulted in
a 16% reduction in MPS at rest despite moderate dietary protein
intake (1.5 g·kg1·day1), with corresponding reductions in
signaling pathways involved in the protein translation protein
E4-EBP1 (53). Similar findings were observed following 5
days of energy restriction (energy availability of 30 kcal·kg
FFM1·day1), resulting in 30% reduction in MPS amongst a
group of young resistance trained volunteers, with corresponding
reductions in activation of mTOR and P70S6K, protein kinases
that regulate protein synthesis (54). However, a single resistance
training session was able to restore MPS to levels observed
in energy balance and this was further enhanced by protein
ingestion (15–30 g) post-exercise, resulting in elevation of MPS
30% above those observed at rest when in energy balance.
Taken together, these acute investigations confirm an energy
deficit can impair the molecular machinery involved in protein
synthesis, but the overall impact on MPS will depend on
other relevant factors such as dietary protein intake and
resistance exercise.
The complex interaction between resistance training and
diet in an energy deficit has also been explored chronically.
In one study, 21 obese women were randomized to either
a control arm or a resistance training arm and fed a very
low energy liquid formula diet (3,369 kJ·day1containing
80 g protein, 97 g carbohydrate, 10 g fat) for 90 days. The
control group and weight training group lost 16.2 and
16.8% of their body mass, respectively. Changes in body
mass, FM, and FFM were similar between groups. However,
muscle biopsies revealed an increase in the cross-sectional
area of fast twitch muscle fibers (55). In another study on
31 women (69 ±12 kg, 164 ±6 cm) who engaged in 24
weeks of combined resistance and endurance training found
that the cross-sectional area of thigh muscle, measured by
magnetic resonance imaging, increased 7 cm, despite a 2.2%
loss in body mass throughout the study (56). Similar gains
in lean body mass (LBM) have been observed amongst
resistance training naive overweight males in response to regular
training (6 days per week, including two resistance training
sessions weekly) and a higher protein diet (2.4 g·kg1·day1),
despite a substantial energy deficit (60% of estimated energy
requirements) (34). Thus, skeletal muscle hypertrophy is possible
in an energy deficit, but we propose this response may be
more likely among resistance training naive, overweight, or
obese individuals. The influence of training status on resistance
training response to adjustments in energy balance warrants
further investigation.
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Slater et al. Energy Surplus and Resistance Training
To our knowledge, there are no rigorously controlled
investigations to date that have directly assessed the role of an
energy surplus on resistance training outcomes such as skeletal
muscle hypertrophy and strength/power traits over an extended
period of time. However, there is an array of circumferential
evidence to support the idea that an energy surplus does enhance
gains in FFM, even independent of the resistance training
stimulus. In an early overfeeding study in which 12 pairs of
identical male twins were fed a total energy surplus of 353 MJ
(with 15% of total daily energy intake from protein) over a span
of 100 days (or 4,200 kJ·day1), the volunteers gained an average
of 5.4 kg FM and 2.7 kg FFM (45), despite maintaining a relatively
sedentary lifestyle. There was a high level of intra-pair correlation
among twins, but significant variance between groups of twins,
indicating a significant genetic contribution to the adaptation.
Another overfeeding study explored the effect of a similar energy
surplus (40% above estimated daily needs or 4,000 kJ energy
surplus daily) but with varying levels of protein intake (5, 15,
or 25% of total energy intake) on body composition over an
8-week period. While all groups increased body fat by similar
amounts (3.5 kg) during this tightly controlled metabolic unit
investigation, gains in LBM (3 kg) were only evident with the
two higher protein intakes, suggesting a minimum amount of
dietary protein is necessary to facilitate gains in LBM, even in an
energy surplus (23).
In a preliminary exploration of the combined effects of
an energy surplus and resistance training, it was found that
only those individuals who consumed an energy dense liquid
supplement twice daily on training days observed significant
gains in body mass and FFM, as inferred via hydrodensitometry,
over an 8-week training period (57). Furthermore, there was no
difference in response whether the extra energy was consumed
as carbohydrate or a combination of carbohydrate and protein,
suggesting the energy content of the diet had the biggest
impact on body composition changes when dietary protein
intake is already adequate. This is supported by earlier pilot
work on the influence of an energy surplus on resistance
training adaptations (58). Interestingly, while both investigations
confirmed a favorable influence of an energy surplus on FFM
gains, this was not reflected in strength changes, perhaps
because of the brief duration of training or due to nuances in
the techniques used to assess strength and body composition.
A recently published pilot study on male bodybuilders also
supports the concept of greater body mass and muscle mass
gains with a more aggressive energy intake (282 kJ·kg1·day1),
although further inferences from this study are difficult due to
methodological concerns (59).
While much still needs to be done to understand the
precise role an energy surplus has in facilitating skeletal muscle
hypertrophy, the following discussion explores what is known
about the magnitude of a surplus, macronutrient composition,
and the mechanisms surrounding the role an energy surplus
has on skeletal muscle hypertrophy. Given the lack of research
within this environment, exploration of overfeeding studies,
independent of the resistance training stimulus, are included in
the discussion on this topic. This needs to be considered given
the influence resistance training has on protein metabolism,
highlighting the symbiotic influence of training, and diet on
resistance training adaptations.
ENERGY SURPLUS… HOW MUCH
Common text book recommendations for the energy surplus
required to gain 1 kg of SMM range from 1,500 to 2,000
kJ·day1in weight stable athletes to an additional 4,000 kJ·day1
in individuals who struggle with lean mass gains or during
heavy training loads (31,32). Guidance on the energy surplus
necessary to facilitate skeletal muscle hypertrophy is often based
solely on the foundation that if 1 kg of skeletal muscle is 75%
water, 20% protein, and 5% fat, glycogen and other minerals
and metabolites, then the energy required to accumulate such
tissue must at a minimum equal the sum of its parts. Given
the assumed composition of skeletal muscle, the energy stored
in 1 kg of muscle is 5,000–5,200 kJ, with 3,400 kJ from
protein, 1,400–1,500 kJ from fat, and 300–450 kJ from muscle
glycogen. Furthermore, energy intake should also be sufficient
to supply substrate to fuel the protein synthetic machinery
stimulated by resistance exercise, a potentially costly process (11,
60). Finally, adequate energy may be needed to account for the
increased metabolic cost of accumulated muscle mass and diet
induced thermogenesis (DIT), all while minimizing additional
energy stored as FM. However, the foundations of these estimates
fail to recognize the complicated and energetically expensive
process of tissue accretion, an energy value which remains to be
systematically quantified. To date, the authors are not aware of
any studies that have clearly demonstrated a consistent energy
cost of tissue accumulation, specifically that which is associated
with skeletal muscle hypertrophy in response to a resistance
training stimulus.
Throughout the twentieth century numerous obesity
researchers investigated the influence an energy surplus has
on body composition. Most studies consistently demonstrate
a strong association between body mass gain and the energy
surplus (61). However, there is large inter-individual variability
in the composition of this mass gain with between 33 and 40%
of body mass accretion accounted for by increases in FFM (61).
In non-exercising populations some have suggested that the
composition of tissue change associated with an energy surplus
is a fixed relationship (62), but in athletic populations where
exercise and adequate protein intake are the main stimuli for
SMM adaptation, this seems unlikely. Of interest from this
obesity research is Forbes and colleagues attempt to estimate
the energy cost of tissue deposition by using theoretical values
of deposition and comparing them to their own findings (22).
They reported that by using the values suggested by Spady et al.
(63), which were 36.2 kJ·g1of protein and 50.2 kJ·g1of fat
deposited, in combination with composition ratios of FM:FFM
observed in their research, that the energy cost of depositing 1 kg
was closely aligned with theoretical values (31,600 and 33,800
kJ·kg1, respectively). As part of this, Forbes surmised that due
to SMM being 20% protein and 75% water, the energy cost
of depositing 1 kg of SMM was 7,440 kJ·kg1. More recently,
Joosen and Westerp (61) have suggested a figure of 29.4 kJ·g1
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Slater et al. Energy Surplus and Resistance Training
of protein deposition, potentially reducing the cost of SMM
deposition to 6,050 kJ·kg1. Both estimates suggest an additional
energy cost to deposit tissue above the energy density of the
substrate (i.e., 16.7 kJ·g1for protein) of between 12.7 and 19.5
kJ·g1protein after overfeeding in non-exercising individuals.
As previously highlighted, research suggests considerable
inter-individual variability in body mass and composition
changes associated with an energy surplus, perhaps as a
consequence of genetics (40,45) or metabolic responses such
as adaptation to DIT or non-exercise activity thermogenesis
(NEAT) (18,64). Numerous mathematical models have been
published to predict changes in body composition associated
with changes in dietary intake and energy expenditure (65,66).
However, these equations often standardize estimates of whole-
body metabolic energy flux due to the non-exercising population
they are focused on (e.g., no change in glycogen state over
time, constant relationships between FM and FFM based on
population norms). In athletic populations, the nature of training
for body composition alterations significantly influences exercise
energy expenditure and confounds the ratios of tissue deposition
these models rely on. Therefore, if practitioners are to provide
guidelines on the energy surplus necessary to synthesize 1 kg
of SMM with minimal FM change, it is necessary that a more
expansive model of energy cost be explored.
A recent review of studies investigating the combination
of a protein focused energy surplus with resistance training
have indicated favorable improvements in LBM accretion (46).
However, to date few studies have focused on a titrated energy
surplus to ascertain the exact energy and nutrient cost of SMM
accretion. It seems to the authors that the energy cost of
SMM accretion would be accounted for by consideration of
several issues. These include the energy stored within muscle
tissue, the energy cost of resistance exercise plus any associated
post-exercise elevation in metabolism, the energy cost of any
subsequent tissue generation, plus it’s subsequent metabolic
function. The metabolic adjustments that occur in response to
an energy surplus also need to be considered. Figure 1 provides
an overview of factors contributing to the energy cost of skeletal
muscle hypertrophy. An appreciation of the magnitude of these
factors would provide greater insight into appropriate energy
intake prescription to facilitate quality weight gain i.e., weight
gain characterized primarily by gains in FFM.
Numerous studies have attempted to estimate the energy
cost of single (67), multiple set (68), and varying speed and
intensity (69) resistance exercise sessions, with the net energy
cost of an 8 exercise (2 sets of 8–10 repetitions per exercise)
hypertrophy program lasting 30 min being 300 and 600 kJ,
for females and males, respectively (70,71). These sex differences
in net energy expenditure are not evident when normalized for
lean mass (72). Given the potential importance of quantifying
energy expenditure, estimates of net resistance training energy
expenditure are available i.e., total energy expenditure (TEE)
minus resting energy expenditure or the specific energy cost of
the resistance training alone. Mookerjee et al. (68) report the
energy cost of undertaking 3 sets of 10 reps at 70% of one
repetition maximum across five upper body exercises (369.4
±174.1 kJ), equating to an energy expenditure of 0.10–0.12
FIGURE 1 | An overview of factors contributing to the energy cost of skeletal
muscle hypertrophy.
kJ·kg1LBM·min1. More recently, a regression equation has
been established to estimate resistance training relative energy
expenditure based on several variables including stature, age, FM,
LBM, and total exercise volume (72), giving practitioners several
options to assist with quantifying the energy cost of resistance
training. While some of these estimates fail to account for any
elevation in energy expenditure post exercise, this effect may only
be evident for upwards of 20 min post exercise (72), and thus
may be considered negligible, at least following shorter duration
resistance training. The metabolic implications of resistance
training warrant further exploration.
Given skeletal MPS is elevated for upwards of 24–48 h after
resistance exercise, the high metabolic cost of protein synthesis
needs to also be accounted for (60,73,74). The process of
translation elongation is likely to account for a large portion
of the synthetic cost with 4 high energy phosphate bonds
per peptide bond formed required or 3.6 kJ·g1of protein
synthesized (75). Although significant, translation is one of
many energy requiring steps in protein synthesis, with processes
such as transcription, folding and movement of proteins within
cells all being energy dependent (52). The high energy cost
of protein synthesis and the duration over which protein
synthetic machinery can be upregulated clearly highlights an
underestimated cost of protein synthesis and thus, muscle mass
accretion. While any associated increase in protein breakdown
has been considered to be negligible, this is unlikely the case
(52). Further research is needed to better quantify the energy cost
of protein synthesis and degradation, plus the time frame over
which this may impact energy needs.
Any increase in LBM will also increase energy expenditure,
both at rest and during exercise due to the addition of
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Slater et al. Energy Surplus and Resistance Training
metabolically active tissue, but the implications of this are likely
substantially less than is often presumed. Indeed, estimates of
the metabolic activity of individual components of FFM suggest
skeletal muscle has an energy cost of just 54 kJ·kg1·day1
(76,77). Given this, the elevation in REE in response to a 1–2 kg
gain in muscle mass is likely very small (i.e., 100 kJ), and within
the precision error of indirect calorimetry techniques available
to quantify REE (78). Less is known about the impact of both
training and an energy surplus on high metabolic activity tissues
like internal organs. However, just 3 weeks of energy restriction
has been shown to significantly decrease liver and kidney mass,
with associated reductions in REE (79), confirming manipulation
of energy balance may impact high metabolic activity tissue size
and thus presumably energy expenditure.
Any adjustment in energy intake away from energy balance
results in an adaptive change in energy expenditure, via
adjustments in NEAT, DIT, and/or adaptive thermogenesis (AT).
Indeed, energy expenditure has been observed to increase after
just 24 h in an energy surplus (40% above estimated needs),
at least when protein intake is concomitantly increased (25).
It has also been proposed that overfeeding induces an increase
in heat production from the food consumed as a protective
mechanism against obesity, a process termed luxuskonsumption
which is claimed to dissipate upwards of 30% of the excess
energy consumed (64). This form of AT has more recently
been challenged by Muller et al. (80) with their assessment
of overfeeding literature suggesting in most studies 60–70%
of excess energy was stored and a further 20–30% accounted
for by metabolic lean mass accretion and increased cost of
movement leaving only about 10% of energy expenditure not
explained and likely accounted for by errors of measurement.
One component of TEE that increases based on changes to the
baseline food consumption is DIT. The DIT associated with a
typical western diet accounts for 8–15% of TEE, depending
on the macronutrient breakdown of the diet (81). In a review
of 26 studies investigating DIT, Quatela et al. (82) used a mixed
model meta-regression process to estimate DIT associated with
overfeeding. They suggested for every 100 kJ of additional energy
from a mixed diet, DIT increased by 1.1 kJ·h1. Energy surpluses
associated with higher protein intakes >3.0 g·kg1BM are likely
to increase this figure further and potentially add an additional
energy requirement compared to surpluses with energy coming
from carbohydrate and fat. This could require an additional 500
kJ a day for athletes with protein intakes in the rage of 3.0
g·kg1·day1compared to intakes of 1.0 g·kg1·day1. Another
significant component of TEE that is highly variable in exercising
individuals, and may be influenced by training and eating, is
NEAT (83). Levine et al. (84) observed a significant increase in
NEAT (1,380 ±1,080 kJ·day1) among individuals over feed
4,200 kJ·day1for 56 days. Although there are some arguments
against this response (64), it is likely this component of TEE
may be highly variable among individuals with different physical
activity levels when in an energy surplus.
Finally, the influence dietary energy intake has on the anabolic
hormonal environment is becoming better understood. It is now
well-established that energy restriction can significantly influence
anabolic hormones in exercising individuals, potentially
impairing their ability to gain and maintain LBM (85). Although
early research by Forbes and colleagues suggested that an energy
surplus could improve anabolic hormone levels in women (86),
few other studies have demonstrated significant increases in the
hormonal environment in response to an energy surplus (87,88).
Irrespective, such acute elevations in circulating anabolic
hormones may have little, if any, impact on resistance training
adaptations (89,90). Thus, any benefit of an energy surplus is
likely mediated via mechanisms other than acutely influencing
the anabolic hormonal environment.
What is clear from the existing literature is that there is
yet to be defined a single evidence-based energy estimate for
accretion of 1 kg of SMM. This is most likely because of the
impact of individual presenting nuances (age, genetics, prior
training experience, sex, body composition) as well as adaptation
to the energy surplus. Figure 2 provides a theoretical overview of
the energy cost of generating SMM typically reported amongst
resistance training individuals (91), the results of which are
similar to that estimated previously (22). A better understanding
of these variables and their impact on resistance training
induced skeletal muscle hypertrophy may afford better individual
prescription of the energy surplus. Until then, practitioners
are advised to take a conservative approach to creating an
energy surplus, within the range of 1,500–2,000 kJ·day1, to
minimize FM gains, with regular review of body composition
and functional capacities like strength to further personalize
dietary intake.
ENERGY SURPLUS… MACRONUTRIENT
CONSIDERATIONS
Within the constraints of an athlete’s total daily energy intake,
considering appropriate allocation of protein, carbohydrate, and
fat may also have a measurable impact on skeletal muscle
hypertrophy. Dietary protein has long been identified as a critical
macronutrient to consider in skeletal muscle repair and synthesis.
Indeed, resistance trained athletes have advocated high protein
diets for many years (10). While debate continues on the need
for additional protein amongst athletes, general guidelines now
recommend that athletes undertaking resistance training ingest
approximately twice the current recommendations for protein of
their sedentary counterparts or as much as 1.6–2.2 g·kg1·day1
(92). In a recent meta-regression of 49 studies including 1,863
male and female participants, the protein intake associated with
the greatest gains in muscle mass was 1.6 g·kg1·day1(18).
Exceeding this upper range of protein intake guidelines likely
offers no further benefit and simply promotes increased amino
acid catabolism and protein oxidation (14). Even extremely
high protein intakes, up to double that advocated (18), does
not further facilitate skeletal muscle hypertrophy or strength
gains (9395).
Despite a lack of apparent benefits from a high protein
diet, athletes who are particularly sensitive to gains in FM
may be tempted to source additional energy to facilitate an
energy surplus from protein, given it is suggested to be less
lipogenic, presumably because of increased DIT (96). However,
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Slater et al. Energy Surplus and Resistance Training
FIGURE 2 | A theoretical overview of the energy cost of generating skeletal muscle mass typically reported amongst resistance training individuals.
the impact on DIT is small in absolute terms and thus unlikely
to significantly influence the response to an energy surplus (97).
While it has been claimed protein, and thus energy intake, can
be increased substantially without promoting gains in FM (93
95,98), it is difficult to understand how this is possible, even
after considering the impact on DIT. Indeed, tightly controlled
research exploring the impact of variable protein intakes while
overfeeding in a metabolic hospital ward confirms protein intake
impacts lean mass while the energy surplus alone contributes to
increases in FM, at least amongst sedentary individuals (23).
Despite previous concerns that high protein diets may be
harmful, healthy adults with protein intakes of 1.8 g·kg1·day1
show no adverse effect on renal function (99). Furthermore,
very high protein diets (2.5–3.3 g·kg1·day1) consumed over
a year had no deleterious effects on blood lipids, liver, or
renal function (100). However, the health implications of very
high protein diets over longer periods is yet to be elucidated.
Taken collectively, it is hard to justify the very high protein
intakes consumed by some resistance training athletes, given
the current lack of supporting research in enhancing resistance
training adaptations, nor research confirming such high intakes
are without health implications.
In addition to protein requirements, consideration must also
be given to appropriate allocation of carbohydrate and fat in
a meal plan attempting to facilitate muscle hypertrophy. Short
term overfeeding studies in sedentary populations confirm there
is no significant difference in body composition changes whether
the energy surplus comes predominantly from carbohydrate or
fat (101,102). However, the metabolic implications of exercise
must be considered amongst resistance trained individuals.
Given the primary substrate used during resistance training
is carbohydrate (103), it is logical to explore the provision
of additional carbohydrate to help support training demands.
This may be especially so for athletes other than weightlifters,
powerlifters, and bodybuilders, where resistance training is
typically undertaken as an ancillary form of training to
complement sport specific training. Resistance training can
reduce muscle glycogen stores by 30–40% (104). Therefore, larger
volume, hypertrophy focused resistance training may necessitate
additional carbohydrate to facilitate resistance training work
capacity (105,106) and restore muscle glycogen (107). While
it is difficult to confirm further enhancement in acute training
capacity (108) or chronic body composition adaptations (58),
when contrasting a moderate vs. high carbohydrate intake, a
chronic restrictive carbohydrate intake may impair resistance
training adaptations. Indeed, SMM gains have consistently been
impaired in studies of resistance trained individuals following
high fat, “ketogenic” diets when compared to moderate intakes
(109111). Given this, it seems reasonable to continue to support
carbohydrate intakes within the range of 4–7 g·kg1·day1for
strength trained athletes (112), with upper ranges advocated for
those undertaking resistance exercise as an ancillary form of
training to complement sport specific training.
The American College of Sports Medicine advises athletes
to keep fat intakes in line with general health guidelines (113),
which constitutes 20–35% of energy intake. Athletes should be
discouraged from fat intakes below 15–20% of energy intake since
such restrictions likely moderate the energy density of a meal
plan, making it challenging to facilitate an energy surplus while
also reducing intake and absorption of fat-soluble vitamins (114,
115). Furthermore, reducing dietary fat from 33.3 to 13.9% of
total energy intake resulted in modest but significant reductions
in resting testosterone concentrations (116), a result which has
been replicated elsewhere (117,118). However, the relevance of
these small changes in circulating androgens is unknown in the
context of chronic resistance training adaptation.
Given the energy density of fat is effectively double that of
carbohydrate and protein, it is logical to consider increasing
fat intake when attempting to increase the energy density of
a meal plan. Indeed, within hypermetabolic clinical conditions
such as cystic fibrosis requiring a high energy intake, increasing
fat intake is advocated (119). Fat source may also determine the
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fate of excess energy, with polyunsaturated fat more likely to
promote gains in lean mass compared to saturated fat, which
is more likely to result in ectopic and general fat accumulation
in normal weight volunteers (120). Evolving evidence suggests
omega-3 polyunsaturated fatty acid ingestion enhances the
anabolic response to nutritional stimuli and increases muscle
mass and function in young and middle-aged males (121), plus
older adults (122), respectively, independent of the resistance
training stimuli. There are also health benefits to consider
in the type of fat consumed. Postprandial fat oxidation is
higher after monounsaturated (olive oil) compared to saturated
(cream) fat meals (123). Simply substituting saturated fat for
unsaturated fat, predominantly as monounsaturated fat, was
enough to induce favorable improvements in lipid profile and
reductions in fat mass in a small sample of overweight and
obese males (124). Whilst interesting, further research is required
to determine whether the potential benefits in the type of fat
ingested are maintained in an athletic population undergoing
resistance training in an energy surplus and whether this
influences the quality of weight gain. Until then, international
recommendations indicate that active individuals may consume
up to 35% of their daily energy intake from dietary fat,
with saturated fatty acids not exceeding 10% of total energy
intake (114).
The type of foods from which macronutrients are sourced
may also have implications on lean mass gains. Protein type is
important as high biological value protein sources rich in leucine
are recommended to maximize protein synthetic rates (125).
Consumption of protein in its natural whole-food matrix may
also differentially stimulate muscle anabolic properties compared
to isolated proteins particularly post resistance training (126).
This has been observed with whole milk compared to skim
milk (127), and whole eggs compared to egg whites (126). Thus,
additional nutrients found in whole foods may offer advantages
beyond their amino acid profile to maximize protein synthesis
(128), although more research is required to ascertain how this
occurs and if benefits remain when total dietary protein and
energy is matched.
In conclusion, insufficient data exists to promote an energy
surplus that comes primarily from any specific macronutrient.
Thus, without further research we can only emphasize that
the minimum intakes of macronutrients advised in this
section be achieved while ensuring an appropriate energy
surplus. Preliminary evidence suggests extra protein may be
less lipogenic, perhaps because of an increase in energy
expenditure associated with DIT, although this needs to be
confirmed with better controlled studies on resistance training
populations and may need to merely be corrected by further
increasing energy intake if the same energy surplus is desired.
Furthermore, the health implications of sustained protein
intakes above 2.5 g·kg1·day1remain to be validated. As
such, other factors such as individual preference, allocation
of extra energy over the day relative to resistance training,
existing energy density of the meal plan and potential for
increasing the volume of existing food/ fluid intake may be a
higher priority when considering the source of any prescribed
energy surplus.
ENERGY SURPLUS… NUTRIENT TIMING
Nutrient timing has received significant attention in recent years
(129), with interventions aiming to optimize work capacity
during exercise and/or facilitate training adaptations. Specifically,
primary attention has been given to the timing of protein
and carbohydrate intake to support acute fuelling and recovery
goals (130), plus facilitate chronic skeletal muscle hypertrophy
adaptations (18). However, whenever daily macronutrient
distribution is adjusted, so too potentially is energy intake. Thus,
the influence of daily energy distribution, including the number
of eating occasions, also warrants consideration.
Athletes are encouraged to pay attention to dietary intake pre,
during and post exercise, under the assumption that nutritional
strategies can influence both acute resistance exercise capacity
and/ or training induced adaptations. Indeed, evidence is present
for a beneficial role of acute carbohydrate ingestion before
and/ or during strength training (105,131). However, not all
investigations show a benefit of acute carbohydrate ingestion
(132134), suggesting the ergogenic potential for carbohydrate
ingestion is most likely to be observed when athletes are
undertaking longer-duration, high-volume resistance training
in isolation, or when resistance training is incorporated into a
higher volume total training load that also includes sports specific
training. Currently, specific recommendations for an optimum
rate or timing of carbohydrate ingestion for resistance trained
athletes before and during a resistance training session cannot
be made within broader guidance of 4–7 g·kg1body mass daily
(112). However, this warrants investigation given the potential
for enhanced substrate availability, plus better alignment of
energy intake to expenditure.
The consumption of high biological value protein containing
meals/snacks in close proximity to training is widely applied
as a strategy to augment the skeletal muscle adaptive response
to resistance exercise (135). Less is known about the impact of
protein distribution in the meal plan outside of the acute period
before and/or after exercise (<3 h). There is some evidence
to suggest that skeletal MPS may be enhanced with a wider
distribution of daily protein intake compared with an acute
bolus of protein (17). Indeed, spacing protein-containing meals
(0.3 g·kg1of high biological value protein) every 3–5 h
throughout the waking period of the day has been advocated
when attempting to maximizes MPS (92), although this remains
to be validated amongst resistance trained individuals when
ingesting protein as part of mixed macronutrient meals while in
energy balance or surplus. Indeed, increasing daily distribution
of high biological value protein from four to six meals per day
had no influence of pre-season gains in lean body mass amongst
a group of rugby athletes (91), suggesting a threshold of daily
protein containing meals, above which there is likely no further
enhancement in skeletal muscle hypertrophy when in energy
balance/surplus, perhaps due to the hypothesized refractory
period that follows acute protein ingestion (136).
While skeletal MPS is unlikely to be further enhanced by
more frequent eating occasions, smaller more frequent eating
occasions (5–6+) are advocated when attempting to increase
muscle mass, presumably because gastrointestinal tract tolerance
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is higher with more frequent eating occasions compared to
merely increasing the size of existing eating occasions (31).
Indeed, smaller, more frequent meals are advocated clinically in
the management of early satiety, anorexia and gastrointestinal
symptoms (137). Emerging evidence supports this notion, with
significantly stronger hunger and desire to eat when following a
smaller, more frequent eating pattern (138). This is corroborated
by preliminary data in elite athletes, with a moderate association
between meal frequency and total energy intake (139). Given
that snacks accounted for approximately one-quarter of total
energy intake in this athletic population, it seems pertinent
to advocate the inclusion of snacks in the meal pattern of
athletes attempting to increase overall energy intake. Current
evidence suggests athletes ingest food daily typically over 5
eating occasions, including the three main meals, plus snacks
(139,140). The impact of eating occasion frequency on overall
nutrient intake and subsequent resistance training outcomes
warrants investigation in athletic populations. Until then, athletes
are encouraged to consume a minimum of 3 main meals, with the
use of strategic snacks to support fuelling and recovery goals, plus
facilitate skeletal MPS.
Similar to the general population (141), athletes allocate
more of their daily energy intake to the later part of the
day (140,142). The impact of better alignment of daily
energy intake to expenditure, or within day energy balance,
is an emerging area of research interest focused on the
physiological implications of real-time changes in energy intake
and expenditure. Preliminary research suggests unfavorable
metabolic and endocrine perturbations with large acute or
extended energy deficits amongst athletes focused on leanness
(143145). The implications of manipulating within day energy
balance amongst resistance training athletes attempting to
promote quality weight gain has not been investigated but
warrants consideration.
There is some preliminary evidence to suggest better
alignment of energy intake to expenditure may have application
in facilitating resistance training outcomes. Ingestion of
a creatine monohydrate containing carbohydrate-protein
supplement immediately before and after resistance training
results in more favorable resistance training adaptations than
when the same supplement is ingested away from training (146),
although this is not always evident, at least when a lower energy,
protein only supplement is ingested according to a similar
time frame (147). While it is impossible to ascribe this effect
to the timing of macronutrient or energy intake, this approach
toward optimizing nutrition support before and after a resistance
training session also supports general fuelling and recovery goals.
It also better aligns acute energy intake to expenditure, given
daily energy expenditure is likely highest during exercise.
For athletes focused on facilitating quality weight gain,
consideration of temporal energy patterns may also be warranted
given preliminary research suggesting an association between
eating more of the day’s total energy intake at night and obesity
(148,149). This may be due to the metabolic dysfunction induced
by delayed eating, even amongst normal weight individuals
(150), or it may merely reflect behavioral mechanisms that
influence appetite control (151). Indeed, intake in the late
night also appears to lack satiating value, resulting in greater
overall daily intake (152). While tempting to advocate athletes to
“front end” more of the daily energy intake, especially amongst
individuals aiming to minimize fat mass gains, moderating
energy intake as the day progresses may be inappropriate for
those with high energy needs and/ or those with significant
training commitments in the evening. Indeed, there is evidence
of enhanced strength and muscle mass gains from resistance
training undertaken in the evening when two protein containing
meals are ingested prior to bed compared to one (153). As
such, manipulation of daily energy distribution should merely
be a variable practitioners consider when providing advice to
athletes, adjusting according to the individual athlete and their
unique circumstances, including specific energy needs, timing
of training, and nutrition goals. The influence of daily energy
distribution warrants investigation amongst resistance trained
athletes attempting to facilitate quality weight gain.
While it is logical to encourage energy intake to vary over
a training week to reflect exercise energy expenditure, athletes
do not always adjust intake to reflect expenditure (154), perhaps
in part because of the variable impact exercise has on appetite
(155). If the creation of a positive energy balance is desired to
facilitate resistance training adaptations, one variable to consider
is whether that energy surplus should be applied throughout the
week or just on resistance training days. Supplemental energy
has typically only been provided on resistance training days
in the limited research in which a positive energy balance has
been achieved in conjunction with resistance training (57). While
this better mirrors energy intake to expenditure, it could be
argued given that skeletal MPS is elevated for upwards of 48 h
following a single resistance training session (43), that a positive
energy balance is also warranted for upwards of 24–48 h post
training. Presumably the creation of a positive energy balance
on both resistance training and non-training days may help to
optimize the potential for enhanced skeletal muscle hypertrophy.
This issue warrants further investigation in resistance trained
populations, especially amongst those individuals aiming to
facilitate quality weight gain. The concept of intermittent energy
restriction shows preliminary potential for facilitating more
effective quality weight loss by moderating any associated
metabolic adjustments (156). It would be interesting to explore
if the reverse was also true with the intermittent application
of a positive energy balance for facilitating quality weight gain.
Indeed, there is preliminary evidence to suggest an acute energy
surplus (facilitated via an increase in all macronutrients) results
in preferential gains in fat free mass (157).
MANAGING SATIETY
Attempts to increase total energy intake by merely increasing
the total volume of food ingested may result in early satiety,
limiting the potential for creation of an energy surplus. Thus,
consideration may need to be given to increasing the energy
density of the meal plan. While increasing dietary fat intake is
a logical option, other novel strategies to better manage early
satiety include changing the food form. For example, regardless
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of the predominant energy source, drinks have lower satiety than
solid foods and thus, provide greater potential for facilitating
a positive energy balance (158,159). Furthermore, nutritious
drinks can be particularly practical following exercise when the
appetite may be suppressed, while also supporting nutritional
recovery goals. A high intake of low energy density vegetables
may also moderate total energy intake at a meal (160). However,
given the health benefits of individuals achieving public health
guidance on vegetable intake (161), practitioners are advised to
balance the pursuit of enhancing energy density with overall
health benefits of the meal plan. Advocating the ingestion of only
moderate servings of protein rich foods at meals may also be
appropriate, given the satiating effect of protein (162), although
the implications of higher protein meals on satiety when in a
positive energy balance remain to be confirmed. However, given
moderate protein servings will also help optimize the skeletal
muscle protein synthetic response (92), guidance on moderated
protein servings appears logical.
FUTURE DIRECTIONS
Further research into this area is clearly warranted, but
challenged by individual responsiveness, including the potential
for rapid metabolic adjustment to the energy surplus and the
need to consider not only the energy surplus, but potentially
where that energy comes from and how it is allocated in the
meal plan over the day relative to the resistance training stimulus.
Methodological issues associated with the quantification of key
outcome measures such as energy intake, energy expenditure
and body composition are also very relevant when attempting
to interpret the literature. For example, an increase in dietary
carbohydrate intake to facilitate a positive energy balance will
acutely increase muscle metabolites and associated water content,
significantly influencing estimates of body composition via dual
energy x-ray absorptiometry (163), and other commonly used
techniques, including air displacement plethysmography and
bioimpedance analysis (164), while acute resistance exercise
induced water retention can influence magnetic resonance
imaging estimates of muscle cross-sectional area for at least
52 h (165). Given such physique assessment nuances, concurrent
review of associated functional capacity adaptations would
appear pertinent for future investigations.
Several gaps in the literature have been identified in this
review, which warrant further exploration. Some of these are
expanded upon here in the hope of facilitating research interest
in this area. A broader understanding of these issues has the
potential to not only impact on dietary guidance for athletic
populations, but also clinical populations where retention or
promotion of SMM is advocated.
Should the Prescribed Energy Surplus Be
Adjusted Based on the Anticipated Muscle
Hypertrophy Potential of the Athlete?
Younger, less experienced athletes have a greater potential for
skeletal muscle hypertrophy in response to resistance training
than their more experienced counterparts (38). It could be argued
that if the energy surplus is merely required to contribute the
building blocks of newly generated tissue, then the prescribed
energy surplus should be adjusted based on muscle hypertrophy
potential. Preliminary research in a small group of elite
Norwegian athletes supports this hypothesis (166). However,
if the energy surplus facilitates a physiological response that
amplifies the anabolic signal created by resistance training, then
perhaps the energy surplus should be maintained in experienced
athletes, at least in these where muscle hypertrophy and strength
gains are prioritized over short term FM increments.
What Factors Influence Whether
Endogenous and/or Exogenous Energy
Sources Can Support the Energy Cost of
Muscle Hypertrophy?
The presence of muscle hypertrophy in response to resistance
training while in an energy deficit clearly confirms the energy cost
of hypertrophy can be obtained endogenously (34,55,56), but is
more likely evident amongst resistance training naïve, overweight
individuals. Thus, individual nuances such as presenting energy
status and training history may need to be considered when
prescribing energy intake.
Does Better Temporal Alignment of Daily
Energy Intake to Expenditure (Within Day
and Between Day) Result in More
Favorable Gains in FFM Relative to FM
When in an Energy Surplus?
While preliminary research suggests unfavorable metabolic and
endocrine perturbations with large acute, within day energy
deficits amongst athletes (144,145), less is known about the
potential benefit of better aligning daily energy intake to
expenditure when in an energy surplus. Encouraging preliminary
research indicates a more favorable response to resistance
training when more of the daily energy intake is allocated
immediately before and after exercise (146). The influence of
better aligning daily energy intake to expenditure across a
training week also warrants investigation, the results of which
would help to identify if any energy surplus should be applied
on raining days only or throughout the training week.
CONCLUSIONS
The creation of an energy surplus is commonly advocated
by sports nutrition practitioners when attempting to optimize
resistance training induced skeletal muscle hypertrophy. Such
guidance is often based solely on the assumed energy stored
within the tissue being assimilated. Unfortunately, this fails to
account for other energetically expensive processes, including
the energy cost of tissue generation, plus the metabolic
adjustments that occur in response to an energy surplus.
An appreciation of the magnitude of these factors would
provide greater insight into appropriate energy prescription to
facilitate optimal rates of muscle hypertrophy while minimizing
fat mass gain. Until that time, practitioners are advised to
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Slater et al. Energy Surplus and Resistance Training
start conservatively with an energy surplus within the range
of 1,500–2,000 kJ·day1and closely monitor response to
the intervention, using changes in body composition and
functional capacity to further personalize dietary interventions.
So long as minimum guidelines for macronutrients advocated
for resistance training individuals are achieved, there does
not appear to be any metabolic or functional benefit to
the source of the energy surplus, affording the practitioner
an opportunity to adjust intake based on other variables
such as existing energy density of the meal plan, eating
occasions and distribution of energy, and macronutrient intake
relative to training, plus potential for further increasing
food intake.
AUTHOR CONTRIBUTIONS
BD, DM, EH, GS, GJS, and JI drafted, critically reviewed,
and revised the manuscript for important intellectual content,
contributed to manuscript revision, read, and approved the
submitted version.
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Conflict of Interest Statement: The authors declare that the research was
conducted in the absence of any commercial or financial relationships that could
be construed as a potential conflict of interest.
Copyright © 2019 Slater, Dieter, Marsh, Helms, Shaw and Iraki. This is an open-
access article distributed under the terms of the Creative Commons Attribution
License (CC BY). The use, distribution or reproduction in other forums is permitted,
provided the original author(s) and the copyright owner(s) are credited and that the
original publication in this journal is cited, in accordance with accepted academic
practice. No use, distribution or reproduction is permitted which does not comply
with these terms.
Frontiers in Nutrition | www.frontiersin.org 15 August 2019 | Volume 6 | Article 131
... An important consideration for PL is that official weigh-in time for most drug-tested federations occur ≤2 h prior to competition (Ferland & Comtois, 2019), compared with 24 h to 36 h in combat sports (Artioli et al., 2016;Reale et al., 2017). With such discrepancies of weigh-in timing and their relationship to muscle recovery, nutrition and physiological adaptations, fluid and carbohydrate stores may be compromised in PL athletes (Nolan et al., 2020), particularly when considering hypohydration and low muscle glycogen can negatively impact strength outcomes (Leveritt & Abernethy, 1999;Schoffstall, Branch, Leutholtz & Swain, 2001;Slater et al., 2019). With this is mind, the aim of the study was to assess the frequency with which certain RWL methods are adopted by male and female PL athletes in the United Kingdom (UK) during competition preparation. ...
... Interestingly, additional strategies (registered response as 'sometimes' in competition preparation) adopted by UK-based PL athletes include dietary manipulations such as skipping meals and fasting (27% and 43%, respectively; Table A.1). A wellestablished relationship exists with respect to muscle mass, lifting performance and energy intakes within resistance trained individuals (Slater et al., 2019;Vargas & Winter, 2021), however it could be hypothesized that the adopted techniques of skipping meals and/or fasting may be counter-productive to a PL athlete's objectives. It has been proposed that acute adoption of a low carbohydrate diet may not be detrimental to resistance exercise performance, or associated cellsignaling activities responsible for muscular adaptation (Escobar, VanDusseldorp & Kerksick, 2016), with evidence suggesting that signaling of protein synthesis remains unaffected by carbohydrate restriction or low muscle glycogen concentrations (Cholewa, Newmire & Zanchi, 2019;Escobar et al., 2016), however carbohydrate hypercaloric dietary intake appears optimal for enhancing muscle hypertrophy (Cholewa et al., 2019). ...
... It could be hypothesized that any resulting implications of RWL (e.g. dehydration, muscle glycogen depletion etc.) may hinder PL athletes' performance during a competition period, a statement that may be particularly pertinent given the relationship between muscle mass, lifting performance and energy surplus in resistance trained individuals (Slater et al., 2019;Vargas & Winter, 2021). Secondly, despite attempts to recruit within the Masters One category, no responses were received as part of the present study. ...
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Previous research in Powerlifting (PL) has qualitatively investigated rapid weight-loss (RWL) in PL athletes and body image, however limited research exists in quantifying such methods adopted in PL. This study aimed to assess the frequency of RWL methods are adopted by male and female PL athletes in the United Kingdom (UK) during competition preparation. A total of n = 37 (n = 19 female, n = 18 male) competitive powerlifters completed an anonymous online questionnaire assessing RWL methods. A Chi-square cross tabulation was utilised to identify any significant differences between independent and dependent variables. Multiple regression analyses were then conducted to assess the contribution of biological sex and PL category on RWL methods. Commonly reported methods of weight loss were gradual dieting (49%), fluid restriction (46%), and water loading (51%). Differences between PL category (Junior, Open, Masters One) and adopting RWL were observed (X 2 =4.220, p <0.05). PL category was a predictor of undertaking RWL (R 2 adj = 0.160, F (2, 34) = 4.429, p ≤ 0.05), whilst biological sex was a predictor of timeframe of undertaking RWL (R 2 adj = 0.123, F (2, 34) = 3.534, p ≤ 0.05). RWL strategies are adopted by PL athletes in order to make weight for competition. Despite known effects of RWL on strength performance, limited research currently exists on these strategies specifically within PL, therefore this may be a consideration for future research. Practitioners working with PL athletes may wish to consider appropriate nutrition and weight loss strategies in preparation for PL competitions.
... Adherence to prescribed protein intake levels was monitored by study staff throughout the study for both groups. Additionally, both groups were prescribed a caloric surplus of 200-300 kcal based on the Harris-Benedict equation using the moderate activity factor in order to potentiate skeletal muscle hypertrophy [45]. Participants were also instructed to consume 3-5 g of carbohydrates per day based on recommendations from Slater and Phillips [46]. ...
... While it is possible that energy intake was underreported in the present study, it remains plausible that a lack of sufficient energy intake contributed to a lack of significant gain in overall lean/soft tissue mass. Given the high bioenergetic cost of de novo MPS over and above simple regulatory muscle protein turnover [45], participants were likely poorly bioenergetically positioned to accrue lean/soft tissue mass. It is additionally possible that participants experienced hypertrophy only in those areas most heavily recruited by study protocols, namely, the lower extremity. ...
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Many studies have evaluated the effects of resistance training (RT) and protein intake to attenuate the age-related loss of skeletal muscle. However, the effects of graded protein intake with conjunctive RT in older adults are unclear. Older adults (n = 18) performed 10 weeks of whole-body RT with progressions to intensity and volume while consuming either a constant protein (CP) diet (0.8–1.0 g/kg/d) with no protein supplement or a graded protein (GP) diet progressing from 0.8 g/kg/d at week 1 to 2.2 g/kg/d at week 10 with a whey protein supplement. Data were collected prior to commencement of the RT protocol (PRE), after week 5 (MID), and after week 10 (POST). Dual Energy X-ray Absorptiometry derived lean/soft tissue mass, ultrasonography derived muscle thickness, and a proxy of muscle quality were taken at PRE and POST, while isokinetic dynamometry derived peak torque were taken at PRE, MID, and POST. This study demonstrated the feasibility of the RT protocol (attendance = 96%), and protein intake protocol (CP in range all weeks; GP deviation from prescribed = 7%). Peak torque, muscle quality scores, and appendicular lean/soft tissue mass demonstrated the main effects of time (p < 0.05) while no other main effects of time or group * time interactions were seen for any measure. In conclusion, RT improved appendicular lean/soft tissue mass, peak torque, and muscle quality, with no differential effects of graded or constant protein intake.
... Rather, a major limiting factor for muscle growth appears to be the temporary desensitization of skeletal muscle to the anabolic effects of food. Considering this refractory period, Norton and needed to achieve a hypercaloric state, the most optimal energy balance for muscle growth 80 . Apart from food, many athletes incorporate supplements for performance-enhancing benefits. ...
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A complex network of biochemical pathways carries out the process of muscle regeneration/growth following resistance exercise. The initial inflammatory response following muscle damage is primarily mediated by the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB), cyclooxygenase enzymes, and prostaglandins. Muscle damage also stimulates the activation, proliferation, differentiation, migration, and fusion of satellite cells onto damaged myofibers, resulting in myofibrillar hypertrophy. The progression of the myogenic lineage is predominantly coordinated by the wingless/integrated family of glycoproteins which engages in crosstalk with NF-κB and the mitogen-activated protein kinase (MAPK)/extracellular signaling-regulated kinase network. The MAPK cascade is essential for mechanotransduction, the process of converting mechanical stimuli into biochemical responses such as accelerated protein synthesis and satellite cell activation. Muscle protein synthesis is primarily governed by the insulin-like growth factor 1/phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin pathway. Several calcium-dependent pathways are also integrated into the process of myogenesis and influence skeletal muscle plasticity. These dynamic interactions are part of the anabolic priming by resistance exercise effect, which defines resistance exercise as an acute catabolic event that potentiates multiple downstream anabolic pathways. Plateaus in muscle growth are attributed to deteriorating inflammatory signaling with repeated bouts of muscle damage as well as increasing thresholds for continuous adaptations, which ultimately become unreachable beyond a certain point. The physiological ceiling of skeletal muscle mass is also credited to myostatin. However, recent discoveries suggest the role of myostatin is not limited to preventing excessive skeletal muscle hypertrophy.
... may have decreased their ability to add de novo muscle tissue to their body. However, the role of total energy availability for skeletal muscle growth in response to resistance exercise is not very well understood and a benefit for increased energy intake has yet to be supported by direct evidence 64 . Taken together, the collective reports in the literature and the data from this current study suggest that to maintain muscle mass with aging and for muscle to adapt to exercise stimuli, perpetual mTORC1 activity is undesirable. ...
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The molecular responses to acute resistance exercise are well characterized. However, how cellular signals change over time to modulate chronic adaptations to more prolonged exercise training is less well understood. We investigated anabolic signaling and muscle protein synthesis rates at several time points after acute and chronic eccentric loading. Adult rat tibialis anterior muscle was stimulated for six sets of ten repetitions, and the muscle was collected at 0 h, 6 h, 18 h and 48 h. In the last group of animals, 48 h after the first exercise bout a second bout was conducted, and the muscle was collected 6 h later (54 h total). In a second experiment, rats were exposed to four exercise sessions over the course of 2 weeks. Anabolic signaling increased robustly 6 h after the first bout returning to baseline between 18 and 48 h. Interestingly, 6 h after the second bout mTORC1 activity was significantly lower than following the first bout. In the chronically exercised rats, we found baseline anabolic signaling was decreased, whereas myofibrillar protein synthesis (MPS) was substantially increased, 48 h after the last bout of exercise. The increase in MPS occurred in the absence of changes to muscle fiber size or mass. In conclusion, we find that anabolic signaling is already diminished after the second bout of acute resistance type exercise. Further, chronic exposure to resistance type exercise training results in decreased basal anabolic signaling but increased overall MPS rates.
... However, because the distribution of the gained tissue, that is, adipose versus lean tissue, is unknown, it is not possible to firmly establish the predictive quality of these numbers. 18 Typically, active individuals engaged in resistance training are advised to initially implement a conservative energy surplus of 360 to 478 kcal/d to induce hypertrophy, 19 which incidentally, approximately reflects the average unadjusted surplus that resulted from the ad libitum approach in this study. ...
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This is a detailed study of nutritional and lifestyle data on a single individual who adhered to the Paleolithic diet (PD) for a full year. The dietary intake was compared with evidence-based guidelines and various PD iterations from the research literature and popular diet books. Although the subject's diet aligned with PD book recommendations, several nutrients differed markedly from estimations in the scientific literature, highlighting the importance of relying on evidence-based dietary advice. These findings provide insight into a contemporary PD in practice, the feasibility of nutrition tracking, and how self-tracked dietary data can inform health behavior.
... 33 Changes in LM were not included in the calculation to avoid autocorrelation issues, considering that LM changes are a primary outcome, as well as the difficulty of quantifying the energy cost of building LM. 34 Further, the impact of LM changes was deemed minor based on both the lack of change in the average energy deficit (<1 kcal day −1 ) and the high correlation between the energy deficit calculated from fat mass changes and the energy deficit calculated from both fat mass and LM (r > 0.95) as well as the similarity between the regression outcomes with and without including changes in LM with an energy value of ~1800 kcal kg −1 . 35 We first regressed our outcome variables on the estimated energy deficit. ...
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Short‐term energy deficits impair anabolic hormones and muscle protein synthesis. However, the effects of prolonged energy deficits on resistance training (RT) outcomes remain unexplored. Thus, we conducted a systematic review of PubMed and SportDiscus for randomized controlled trials performing RT in an energy deficit (RT+ED) for ≥3 weeks. We first divided the literature into studies with a parallel control group without an energy deficit (RT+CON; Analysis A) and studies without RT+CON (Analysis B). Analysis A consisted of a meta‐analysis comparing gains in lean mass (LM) and strength between RT+ED and RT+CON. Studies in Analysis B were matched with separate RT+CON studies for participant and intervention characteristics, and we qualitatively compared the gains in LM and strength between RT+ED and RT+CON. Finally, Analyses A and B were pooled into a meta‐regression examining the relationship between the magnitude of the energy deficit and LM. Analysis A showed LM gains were impaired in RT+ED vs RT+CON (effect size (ES) = ‐0.57, p = .02), but strength gains were comparable between conditions (ES = ‐0.31, p = .28). Analysis B supports the impairment of LM in RT+ED (ES: ‐0.11, p = .03) vs RT+CON (ES: 0.20, p < .001) but not strength (RT+ED ES: 0.84; RT+CON ES: 0.81). Finally, our meta‐regression demonstrated that an energy deficit of ~500 kcal · day‐1 prevented gains in LM. Individuals performing RT to build LM should avoid prolonged energy deficiency, and individuals performing RT to preserve LM during weight loss should avoid energy deficits >500 kcal · day‐1.
... Resistance exercise and protein supplementation are known strategies to induce lean mass hypertrophy [104,105]. However, while in an energy deficit state, anabolic suppression (i.e., a blunted training response) during resistance training has been previously demonstrated even in the presence of protein supplementation and adequate daily protein intake of 1.2 g·kg −1 body weight and may explain the lack of lean mass hypertrophy reported in combined fasting and exercise interventions [106,107]. In the same way, fasting and exercise interventions may be able to reduce fat mass independent of weight loss by manipulating energy intake during fed hours, the same concept may apply to achieving an increase in lean mass. ...
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Nutrition and exercise interventions are strongly recommended for most cancer patients; however, much debate exists about the best prescription. Combining fasting with exercise is relatively untouched within the oncology setting. Separately, fasting has demonstrated reductions in chemotherapy-related side effects and improved treatment tolerability and effectiveness. Emerging evidence suggests fasting may have a protective effect on healthy cells allowing chemotherapy to exclusively target cancer cells. Exercise is commonly recommended and attenuates treatment- and cancer-related adverse changes to body composition, quality of life, and physical function. Given their independent benefits, in combination, fasting and exercise may induce synergistic effects and further improve cancer-related outcomes. In this narrative review, we provide a critical appraisal of the current evidence of fasting and exercise as independent interventions in the cancer population and discuss the potential benefits and mechanisms of combined fasting and exercise on cardiometabolic, body composition, patient-reported outcomes, and cancer-related outcomes. Our findings suggest that within the non-cancer population combined fasting and exercise is a viable strategy to improve health-related outcomes, however, its safety and efficacy in the oncology setting remain unknown. Therefore, we also provide a discussion on potential safety issues and considerations for future research in the growing cancer population.
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Sport scholars have argued that to protect athlete health, competitive sport cultures must begin to de-emphasize the importance of leanness for athletic performance. However, there is a notable lack of analyses of the pressures towards leanness experienced by athletes in sports that are not considered most ‘at-risk’ for the development of disordered bodily practices, such as Olympic Weightlifting. Based on interviews with sixteen competitive American Olympic Weightlifters, this study uses Foucauldian insights about the inseparability of culture, language, and the body to examine how weightlifters come to understand—and rationalize—their weight classes, body compositions, and avoidance of body fat. We find that while weightlifters characterized a wide range of body compositions as being functional for the sport, their own weight class choices were informed by a sport-specific narrative that condemned body fat. We critically interrogate this preference for leanness-focused bodily practices in a ‘non-lean’ sport, looking to the ‘Sport Ethic’ and other dominant bodily discourses as possible sources of influence.
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Purpose of Review Sports nutrition guidelines typically state that athletes desiring weight gain follow a regimen that includes increasing energy intake by ~ 300–500 kcal/day with an emphasis on adequate protein and carbohydrate and judicious inclusion of energy-dense foods, in combination with rigorous resistance training. This regimen is thought to promote weekly gains of ~ 0.45 kg (1 lb), mostly as lean body mass (LBM). This review summarizes the evidence supporting these intentional weight gain regimens in athletes. Recent Findings Although some research has been conducted in the past 5 years, research on intentional weight gain is lacking. Summary Currently, available data suggests that weekly weight gain of 0.45 kg (1 lb), primarily as LBM, may be difficult for some athletes to achieve. Available evidence, however, suggests that commonly recommended strategies to promote calorie surplus, including consuming larger portions, incorporating energy-dense foods, and prioritizing liquid over solid foods, may prove helpful.
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Purpose: Resistance training combined with appropriate dietary intake can promote a concomitant increase in skeletal muscle mass (SMM) and reduction in fat mass, a condition termed body recomposition. This study's primary purpose was to explore the effects of protein ingestion on body recomposition following 24 weeks of resistance training (RT) in older women. Methods: Data from 130 untrained older women (68.7 ± 5.6 years, 66.5 ± 11.5 kg, 155.5 ± 6.0 cm, and 27.4 ± 4.0 kg.m-2) across six studies were retrospectively analyzed. The participants were divided into tertiles according to their customary protein intake (g/kg/d): lower (LP, n = 45), moderate (MP, n = 42), and higher (HP, n = 43) protein intake. Participants performed a whole-body RT program carried out over 24 weeks (eight exercises, three sets, 8-15 repetitions, three sessions a week). SMM and fat mass were determined by dual-energy X-ray absorptiometry. Results: All groups increased SMM from baseline (P < 0.05), with the HP and MP groups showing greater increases than the LP group (LP = 2.3%, MP = 5.4%, and HP = 5.1%; P < 0.05). Reductions in fat mass were similar for all three groups (LP = 1.7%, MP = 3.7%, and HP = 3.1%; P > 0.05). The composite Z-score of the percentage changes from pre- to post-training indicated greater positive body recomposition values for HP and MP compared to LP (P < 0.05). Conclusions: Results suggest that protein intake is a moderating variable for body recomposition in older women undergoing RT, with a low protein intake having a less favorable effect on body recomposition.
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The energy expenditure of resistance exercise (RE) is an important consideration for exercise prescription and weight management, yet prediction models are lacking. Purpose: This study aimed to develop regression equations to predict energy expenditure (kcal) for RE involving each major muscle group using commonly measured demographic and exercise variables as predictors. Methods: Fifty-two healthy, active subjects (27 men, 25 women, age 20-58 yr, height 174.1 ± 10.5 cm, weight 188.7 ± 42.6 kg, V˙O2max 36.8 ± 9.2 mL·kg⋅min) were strength tested to estimate their one-repetition maximum 1 wk before their experimental RE bout. The experimental RE bout consisted of a warm-up set followed by 2-3 sets (2-min turnover) of 8-12 reps at 60%-70% of predicted one-repetition maximum for leg press, chest press, leg curl, lat pull, leg extension, triceps push down, and biceps curl. Kilocalories were estimated from V˙O2 measured continuously throughout the RE bout via an automated metabolic cart. Total exercise volume (TV) was calculated as sets × reps × weight lifted. Multiple linear regression (stepwise removal) was used to determine the best model (highest adjusted R) to predict the kilocalorie consumption of the total workout and of the individual RE lifts. Results: The derived regression equation for the net kilocalorie consumption of an RE bout was as follows: total net kilocalorie = 0.874 (height, cm) - 0.596 (age, yr) - 1.016 (fat mass, kg) + 1.638 (lean mass, kg) + 2.461 (TV × 10) - 110.742 (R = 0.773, SEE = 28.5 kcal). Significant equations were also derived for individual lifts (R = 0.62 to 0.83). Conclusions: Net energy expenditure for a total RE bout and for individual RE can be reasonably estimated in adult men and women using commonly measured demographic and RE variables.
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The purpose of this study was to determine the effects of different amounts of energy intake in combination with progressive resistance training on muscle mass and body fat in bodybuilders. Eleven male bodybuilders (26.8 ± 2.3 years, 90.1 ± 9.7 kg, and 176.9 ± 7.1 cm) were randomly assigned into one of two groups: a group that ingested higher amounts of energy (G1, 67.5 ± 1.7 kcal/kg/d, n = 6), and a group that ingested moderate amounts of energy (G2, 50.1 ± 0.51 kcal/kg/d, n = 5). Both groups performed resistance training 6 days per week over a 4-week study period. Measures of body composition were assessed before and after the intervention period. For body fat, only the G1 presented significant changes from pre- to post-training (G1 = +7.4% vs. G2 = +0.8%). For muscle mass, both groups showed significant increases after the intervention period, with G1 presenting a greater increase compared to G2 (G1 = +2.7% vs. G2 = +1.1%). Results suggest that greater energy intake in combination with resistance training induces greater increases in both muscle mass and body fat in competitive male bodybuilders.
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Protein recommendations are provided on a daily basis as defined by the recommended dietary allowance (RDA) at 0.80 g protein/kg/day. However, meal-based, as opposed to daily, dietary protein recommendations are likely more informative given the role of the daily protein distribution pattern in modulating the post-exercise muscle protein synthetic response. Current protein meal recommendations to plateau post-exercise muscle protein synthesis rates are based on the ingestion of isolated protein sources, and not protein-rich whole foods. It is generally more common to eat whole food sources of dietary protein within a normal eating pattern to meet dietary protein requirements. Yet, there is a need to define how dietary protein action on muscle protein synthesis rates can be modulated by other nutrients within a food matrix to achieve protein requirements for optimal muscle adaptations. Recent developments suggest that the identification of an “optimal” protein source should likely consider the characteristics of the protein and the food matrix in which it is consumed. This review aims to discuss recent concepts related to protein quality, and the potential interactive effects of the food matrix, to achieve optimal protein requirements and elicit a robust postprandial muscle protein synthetic response with an emphasis on the post-exercise recovery window.
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Athletes utilise numerous strategies to reduce body weight or body fat prior to competition. The traditional approach requires continuous energy restriction (CER) for the entire weight loss phase (typically days to weeks). However, there is some suggestion that intermittent energy restriction (IER), which involves alternating periods of energy restriction with periods of greater energy intake (referred to as ‘refeeds’ or ‘diet breaks’) may result in superior weight loss outcomes than CER. This may be due to refeed periods causing transitory restoration of energy balance. Some studies indicate that intermittent periods of energy balance during energy restriction attenuate some of the adaptive responses that resist the continuation of weight and fat loss. While IER—like CER—is known to effectively reduce body fat in non-athletes, evidence for effectiveness of IER in athletic populations is lacking. This review provides theoretical considerations for successful body composition adjustment using IER, with discussion of how the limited existing evidence can be cautiously applied in athlete practice.
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Greene, DA, Varley, BJ, Hartwig, TB, Chapman, P, and Rigney, M. A low-carbohydrate ketogenic diet reduces body weight without compromising performance in powerlifting and Olympic weightlifting athletes. J Strength Cond Res XX(X): 000-000, 2018-Weight class athletes use weight-making strategies to compete in specific weight categories with an optimum power-to-weight ratio. There is evidence that low carbohydrate diets might offer specific advantages for weight reduction without the negative impact on strength and power previously hypothesized to accompany carbohydrate restriction. Therefore, the purpose of this study was to determine whether a low-carbohydrate ketogenic diet (LCKD) could be used as a weight reduction strategy for athletes competing in the weight class sports of powerlifting and Olympic weightlifting. Fourteen intermediate to elite competitive lifting athletes (age 34 ± 10.5, n = 5 female) consumed an ad libitum usual diet (UD) (>250 g daily intake of carbohydrates) and an ad libitum LCKD (≤50 g or ≤10% daily intake of carbohydrates) in random order, each for 3 months in a crossover design. Lifting performance, body composition, resting metabolic rate, blood glucose, and blood electrolytes were measured at baseline, 3 months, and 6 months. The LCKD phase resulted in significantly lower body mass (-3.26 kg, p = 0.038) and lean mass (-2.26 kg, p = 0.016) compared with the UD phase. Lean mass losses were not reflected in lifting performances that were not different between dietary phases. No other differences in primary or secondary outcome measures were found between dietary phases. Weight class athletes consuming an ad libitum LCKD decreased body weight and achieved lifting performances that were comparable with their UD. Coaches and athletes should consider using an LCKD to achieve targeted weight reduction goals for weight class sports.