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Abstract

Purpose: Athletes risk performance and muscle loss when dieting. Strategies to prevent losses are unclear. This study examined the effects of two diets on anthropometrics, strength, and stress in athletes. Methods: This double-blind crossover pilot study began with 14 resistance-trained males (20-43 yr) and incurred one dropout. Participants followed carbohydrate-matched, high-protein low-fat (HPLF) or moderate-protein moderate-fat (MPMF) diets of 60% habitual calories for 2 weeks. Protein intakes were 2.8g/kg and 1.6g/kg and mean fat intakes were 15.4% and 36.5% of calories, respectively. Isometric midthigh pull (IMTP) and anthropometrics were measured at baseline and completion. The Daily Analysis of Life Demands of Athletes (DALDA) and Profile of Mood States (POMS) were completed daily. Outcomes were presented statistically as probability of clinical benefit, triviality, or harm with effect sizes (ES) and qualitative assessments. Results: Differences of effect between diets on IMTP and anthropometrics were likely or almost certainly trivial, respectively. Worse than normal scores on DALDA part A, part B and the part A "diet" item were likely more harmful (ES 0.32, 0.4 and 0.65, respectively) during MPMF than HPLF. The POMS fatigue score was likely more harmful (ES 0.37) and the POMS total mood disturbance score (TMDS) was possibly more harmful (ES 0.29) during MPMF than HPLF. Conclusions: For the 2 weeks observed, strength and anthropometric differences were minimal while stress, fatigue, and diet-dissatisfaction were higher during MPMF. A HPLF diet during short-term weight loss may be more effective at mitigating mood disturbance, fatigue, diet dissatisfaction, and stress than a MPMF diet.
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Note: This article will be published in a forthcoming issue of
the International Journal of Sport Nutrition and Exercise
Metabolism. This article appears here in its accepted, peer-
reviewed form; it has not been copyedited, proofed, or
formatted by the publisher.
Section: Original Research
Article Title: High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue
Than Moderate-Protein Moderate-Fat Diet During Weight Loss in Male Weightlifters, A
Pilot Study
Authors: Eric R. Helmsa, Caryn Zinnb, David S. Rowlandsc, Ruth Naidooa, and John
Cronina,d
Affiliations: aSport Performance Research in New Zealand (SPRINZ) at AUT Millennium
Institute, AUT University, Auckland, New Zealand. bHuman Potential Centre at AUT
Millennium Institute, AUT University, Auckland, New Zealand. cSchool of Sport and
Exercise, Massey University, Wellington, New Zealand. dSchool of Exercise, Biomedical and
Health Sciences, Edith Cowan University, Perth, Australia.
Journal: International Journal of Sport Nutrition and Exercise
Acceptance Date: June 5, 2014
©2014 Human Kinetics, Inc.
DOI: http://dx.doi.org/10.1123/ijsnem.2014-0056
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
High-protein low-fat short-term diet results in less stress and fatigue than moderate-
protein moderate-fat diet during weight loss in male weightlifters, a pilot study
Eric R. Helmsa, Caryn Zinnb, David S. Rowlandsc, Ruth Naidooa, John Cronin a,d
aSport Performance Research in New Zealand (SPRINZ) at AUT Millennium Institute, AUT
University, Auckland, New Zealand
bHuman Potential Centre at AUT Millennium Institute, AUT University, Auckland, New
Zealand
cSchool of Sport and Exercise, Massey University, Wellington, New Zealand
dSchool of Exercise, Biomedical and Health Sciences, Edith Cowan University, Perth,
Australia
Eric Helms
Sports Performance Research in New Zealand at AUT Millennium Institute
17 Antares Place, Mairangi Bay, Auckland 0632, New Zealand
Tel: (64) 021638466
E-mail: eric.helms@aut.ac.nz
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Abstract
Purpose: Athletes risk performance and muscle loss when dieting. Strategies to prevent
losses are unclear. This study examined the effects of two diets on anthropometrics, strength
and stress in athletes. Methods: This double-blind crossover pilot study began with 14
resistance-trained males (20-43 yr) and incurred one drop-out. Participants followed
carbohydrate-matched, high-protein low-fat (HPLF) or moderate-protein moderate-fat
(MPMF) diets of 60% habitual calories for two weeks. Protein intakes were 2.8g/kg and
1.6g/kg and mean fat intakes were 15.4% and 36.5% of calories, respectively. Isometric mid-
thigh pull (IMTP) and anthropometrics were measured at baseline and completion. The Daily
Analysis of Life Demands of Athletes (DALDA) and Profile of Mood States (POMS) were
completed daily. Outcomes were presented statistically as probability of clinical benefit,
triviality or harm with effect sizes (ES) and qualitative assessments. Results: Differences of
effect between diets on IMTP and anthropometrics were likely or almost certainly trivial,
respectively. "Worse than normal" scores on DALDA part A, part B and the part A “diet”
item were likely more harmful (ES 0.32, 0.4 and 0.65, respectively) during MPMF than
HPLF. The POMS fatigue score was likely more harmful (ES 0.37) and the POMS total
mood disturbance score (TMDS) was possibly more harmful (ES 0.29) during MPMF than
HPLF. Conclusions: For the two weeks observed, strength and anthropometric differences
were minimal while stress, fatigue and diet-dissatisfaction were higher during MPMF. A
HPLF diet during short-term weight loss may be more effective at mitigating mood
disturbance, fatigue, diet-dissatisfaction and stress than a MPMF diet.
Key Words: macronutrient; anthropometry; resistance training; isometric exercise; athlete.
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Caloric restriction during resistance training is common practice for athletes in
weight-class restricted or aesthetic sport. This is frequently seen among bodybuilders, power
lifters, weight lifters, and combat athletes (Slater & Phillips, 2011; Umeda et al., 2004), the
goal being to improve performance either via increased power-to-weight ratio in performance
sports, or via aesthetic improvement in physique competitions. These performance or
aesthetic improvements are optimized when fat-free mass (FFM) contributes as little as
possible to the mass lost during energy restriction. However, weight loss and caloric
restriction can lead to losses of FFM and performance (Buford, Rossi, Smith, O'Brien, &
Pickering, 2006; Koral & Dosseville, 2009; Umeda et al., 2004). Thus, strategies to minimize
potential losses of FFM and performance during weight loss warrant study.
While it is well established that body composition is most favorably improved in
overweight populations performing resistance training in combination with an increased
protein intake (Demling & DeSanti, 2000; Layman et al., 2005; Stiegler & Cunliffe, 2006),
similar research in resistance-trained athletes is sparse. To date, two studies have measured
performance and body composition in resistance-trained athletes while they consumed
energy-matched hypocaloric diets of differing protein levels (Mettler, Mitchell, & Tipton,
2010; Walberg et al., 1988). The data available from these studies provide insight into the
FFM-sparing potential of high-protein diets in athletes. However, only a handful of intake
levels have been examined (0.8g/kg, 1g/kg, 1.6g/kg and 2.3g/kg per day) which limits the
ability to determine thresholds at which benefits are obtained. However, it seems that as
protein increases FFM retention increases as well.
While upon first glance it appears that a linear relationship with protein intake and
FFM preservation exists, in Pasiakos et al., (2013) a non-significant trend of greater FFM
retention was observed in a group consuming 1.6g/kg of protein compared to a group
consuming 2.4g/kg. However, this trend could have been related to a low carbohydrate-
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
mediated (27% of calories) performance decrease in the resistance training protocol (Walberg
et al., 1988), or because the protocol did not increase protein demands as it was specifically
designed to not provide an anabolic stimulus. Thus, uncertainty remains for thresholds of
beneficial protein intakes in resistance-trained athletes during weight loss.
Therefore, in the context of isocaloric, carbohydrate-matched diets of a 40% energy
deficit, the current study compared 2.8g/kg to 1.6g/kg of protein per day; 2.8g/kg
representing what many strength athletes habitually consume and 1.6g/kg falling within
standard sports nutrition guidelines (Slater & Phillips, 2011). The aim of this pilot study was
to see whether or not a high protein intake above what is typically recommended, yet which
represents what many strength athletes habitually consume, provides any measureable benefit
in terms of mood state, maximal strength or body composition during short term energy
restriction in resistance trained males.
Methods
Fourteen resistance-trained males gave their written informed consent to participate in
this double-blind crossover pilot study approved by the AUT University Ethics Committee
(approval number 12/313). Thirteen participants completed the study. Participants were
required to be: (i) regularly (≥ 2 days per week) resistance training with at least one year of
experience; (ii) weight stable 2%) for at least one month; (iii) healthy as assessed by the
Physical Activity Readiness Questionnaire; (iv) not using anabolic steroids or other illegal
performance enhancing drugs; and (v) below 20% body fat (Durnin & Womersley, 1974) as
assessed by an International Society for the Advancement of Kinanthropometry certified
anthropometrist. Participants were recruited from gyms, weight lifting and crossfit clubs,
supplement stores, and AUT University sports science and nutrition classes. Participant
characteristics are provided in Table 1.
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Eligible participants were taught to track their diets with multiple one on one sessions
with a researcher and once familiarized they each completed a one-week online food diary.
Digital food scales were provided to participants who did not have their own. This diary was
analyzed by the researchers, one of whom is a New Zealand Registered Dietitian, to
determine habitual energy intakes. Diets were developed based on 60% of the energy intake
recorded in the diaries, which was 3049 ± 414kcal per day. Mean protein intake recorded in
the food diaries for the group was 169.4 ± 36.8g or 2.1 ± 0.4g/kg per day when expressed
relative to bodyweight. Participants were randomly assigned to the 14 day dietary
intervention, which was either a high-protein low-fat (HPLF) or moderate-protein moderate-
fat (MPMF) intervention diet. The design of each dietary intervention is shown in table 2. Fat
intake as a percentage of calories provided by HPLF and MPMF was 15.4% and 36.5% of
calories, respectively and the relative intake of fat was 0.4 ± 0.2g/kg and 0.9 ± 0.2g/kg per
day, respectively. Carbohydrate intake relative to bodyweight during both diets was 2.0 ±
0.2g/kg per day. Six of the participants began with HPLF and finished with MPMF and
seven had the opposite order. Food preference questionnaires were used to develop meal
plans for each dietary intervention. Each participant was provided with three meal plans with
equal macronutrients, for variety, and either a pea-protein isolate (Clean Lean Protein
Vanilla; NuZest, New Zealand) only or a pea-protein and maltodextrin mix to make up the
daily intake during each intervention. Pea protein was selected to assist in blinding because of
its thicker texture and infrequent commercial use compared to whey, casein or soy protein.
Similarly, maltodextrin was selected because of its bland flavor. Participants were not
permitted to consume any new supplements or supplements with caloric value, but were
instructed to maintain their existing (zero caloric value) supplementation regime throughout
the two interventions. Details of the intervention diets are provided in Table 2.
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
The dietitian, who was not involved in data collection or analysis mixed the powders,
labeled them “a” or “b” for blinding and retained the blinding key. The primary researcher
was un-blinded to the supplement key only after data analysis was complete. Exit surveys
were not performed to determine the success of the blinding strategy. The participants were
instructed to approach the dietitian for any assistance with dietary matters.
Three participants inadvertently consumed extra or incorrect food items on one
occasion each, and immediately communicated this with the dietitian. Meals for the
remainder of the day were adjusted where possible to ensure that the macronutrient and
energy contributions were not compromised. When the communication was made the day
following the error, meals on that day were adjusted to account for the nutrient shortfall or
excess the day prior, and thereby ensuring an accurate nutrient intake over a two-day period.
Examples of errors included inadvertently adding milk to tea, and consumption of a full-sugar
beverage and full-sugar peppermints, rather than their non-sugar counterparts. All meal plans
were successfully adjusted, thereby maintaining nutrient integrity throughout the study.
After completing the first diet, participants were assigned to a wash out that lasted
approximately twice the length of the intervention diet or longer (25 to 49 days) based on the
scheduling needs of the participant. During the wash out participants were instructed to eat
normally, initially allowing weight regain. Two weeks before starting the second intervention
they were instructed to return to their habitual caloric intake as recorded in their initial food
diaries which they completed prior to beginning their first intervention. Fourteen participants
started the study; however, one dropped out during the first intervention, which for this
participant was MPMF, complaining of fatigue, depression and mental stress.
The day prior to starting and the day after completing each intervention, participants
had their height, weight, eight-site (triceps, subscapular, biceps, iliac crest, supraspinale,
abdominal, front thigh, and medial calf) skinfold thicknesses, waist, hip, calf, relaxed and
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
flexed arm girths, and femur and humerus breadths measured. The anthropometrist had a
technical error of measurement for skinfolds of ± 0.4mm (mean error of six sites). Three
equations were used to analyze FFM (Durnin & Womersley, 1974; Peterson, Czerwinski, &
Siervogel, 2003; Yuhasz, 1974).
Pre and post testing occurred as close to the same time of day as possible for each
individual. On the day of post testing prior to assessment, participants were instructed to
repeat the eating pattern they followed the day of pre testing prior to assessment. Participants
were informed of this requirement the day of pre testing and then reminded again the day
prior to post testing. Participants were instructed to maintain their normal training regimen
during both dietary intervention periods. Additionally, the same exercise and dietary regime
was maintained prior to both pre and post testing. Strength assessment testing peak force
using the isometric mid-thigh pull (IMTP) exercise (Stone et al., 2003) followed
anthropometry. Vertical ground reaction force data were collected at a sample rate of 200 Hz
with a commercially available force plate (400 Series Performance Force Plate;
FitnessTechnology, Australia) connected to computer software (Ballistic Measurement
System, FitnessTechnology, Australia). The force plate was calibrated before each testing
session. Participants used cloth lifting straps to avoid grip-strength limitations. Participants
were instructed on the performance of the assessment, given a visual demonstration, allowed
a practice attempt, and then the best of three IMTP’s was recorded. One participant during
one pre test was unable to properly use the lifting straps and was excluded from the IMTP
analysis for that arm of the crossover. Thus, 12 pre and post tests were included for the IMTP
analysis for that arm of the crossover.
The Profile of Mood States (POMS) short form (Shacham, 1983) and the Daily
Analysis of Life Demands of Athletes (DALDA) (Rushall, 1990) questionnaires were chosen
to quantify the psychological-response to the diets because of their wide use in sport and
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
exercise research (Halson et al., 2002; Mettler et al., 2010; Morgan, Costill, Flynn, Raglin, &
O'Connor, 1988). Every day participants completed the POMS and both part A and B of the
DALDA questionnaire, which represent the general stress sources and the resulting signs and
symptoms, respectively. Each source of stress in part A and each sign or symptom in part B
could be graded as follows: a = "worse than normal", b = "normal” and c = "better than
normal". Total "worse than normal" scores were calculated for part A and part B and total
"worse than normal" scores for the "diet" item in part A were calculated to assess the diet-
related stress, representing the satiety and enjoyment of each dietary intervention.
Participants were instructed to complete questionnaires at the same time on a daily basis. If a
participant missed a day of completing the DALDA in one 14-day dietary intervention, the
same day of the following 14-day dietary intervention was discarded. The POMS
questionnaire provides a measure of the tension/anxiety, depression, anger, vigor, fatigue and
confusion levels of the participant. Each mood item in the POMS was rated on a 5-point scale
as follows: 0 = “not at all”, 1 = “a little”, 2 = “moderately”, 3 = “quite a bit” and 4 =
“extremely”. For each participant a mean of all days reported was calculated for the total
mood disturbance score (TMDS) and fatigue score. The fatigue score was specifically chosen
to help differentiate any effects on TMDS that might have been caused by satiety or diet
preference rather than energy levels, which are of primary concern to athletes. TMDS was
calculated by adding the five negative mood states together and subtracting the positive mood
state, vigor. One participant after one arm of the crossover lost their POMS and DALDA
forms and thus their data for that arm of the crossover was not included, resulting in 12
completed sets of psychometric forms for that portion of the study.
All variables except the POMS TMDS, fatigue score and the DALDA "worse than
normal" diet scores were log transformed before analysis to reduce non-uniformity of error
and to express effects as percent changes (Hopkins, Marshall, Batterham, & Hanin, 2009).
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
POMS TMDS and fatigue scores were averaged over the days reported to provide uniformity
and the DALDA diet score is a single item Likert scale.
A spreadsheet for analysis of a post-only crossover trial (Hopkins, 2012a) was used to
determine differences between the two groups on the POMS and DALDA scores. A
spreadsheet for analysis of a pre and post crossover trial (Hopkins, 2012b) was used to
determine differences between the two groups on the IMTP and all anthropometric variables.
IMTP data was analyzed with bodyweight at the start of the dietary intervention as a
covariate. Mean percentage changes with 90% confidence limits (CL) were presented for pre
and post test variables (IMTP and anthropometric data) and mean scores with 90% CL were
presented for post-only variables (psychometric data). The chances (% and qualitative) that
the true value of each statistic was practically beneficial, trivial, or harmful were calculated
using the spreadsheets. To determine the threshold for an effect, the smallest standardized
change was assumed to be 0.2. For all variables that were measured, thresholds used to
determine the magnitude of effect sizes were based on a modified Cohen’s scale.
Standardized thresholds of <0.2, <0.6, <1.2, and <2.0 were interpreted as trivial, small,
moderate, and large effects, respectively (Batterham & Hopkins, 2006). This approach using
probability statistics allows the reader to make decisions around the use of feedback based on
its predicted beneficial or harmful effects (Batterham & Hopkins, 2006; Hopkins et al.,
2009). Readers unfamiliar with this statistical paradigm and its merits are referred to Batterham
and Hopkins (2006) and Hopkins et al., (2009) for a more in-depth discussion.
Results
Results of all variables measured are provided in Table 3.
All anthropometric markers decreased in both groups over the course of the two-week
dietary intervention. Fat loss as measured by sum of eight skinfolds was almost identical
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
between dietary interventions. A slightly greater amount of bodyweight (0.6%) and FFM
(0.4%) was lost in the MPMF group. The same relative loss of FFM was found when using
each of the three equations that were implemented to assess body composition. However, all
anthropometric differences between diets were very likely or almost certainly trivial.
IMTP strength losses were slightly less (1.1%) for the MPMF group but more than
twice as variable as the HPLF group. However, differences in effect on isometric strength
between diets was likely trivial.
General stress measured by part A of the DALDA, signs and symptoms of stress
measured by part B of the DALDA and the part A “diet” item stress levels were higher in
MPMF compared to HPLF. The effect sizes for these differences were small for part A (0.32)
and B (0.4) of the DALDA and moderate for the part A “diet” item (0.65). POMS fatigue and
TMDS were higher in the MPMF groups as well with small effect sizes (0.37 and 0.29,
respectively) for these differences. Effects of MPMF compared to HPLF on all parts of the
DALDA and POMS fatigue were assessed as likely harmful, and the effect on TMDS was
assessed as possibly harmful. Grams of carbohydrate coming from maltodextrin were
analyzed as a covariate separately to determine if these effects were related to carbohydrate
source rather than amount; however, this analysis did not change the qualitative outcomes.
Discussion
The results of this pilot study are limited to resistance-trained males during short term
caloric restriction. Additionally, the effects of this dietary intervention on performance
outside of maximal isometric strength and indications of mood disturbance are unknown.
Furthermore, our small sample size limits the ability to detect meaningful changes when
dealing with a short term observational period; thus the results of this pilot study should be
seen as preliminary. Finally, the changes observed in FFM are subject to the inherent error
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
present in body composition equations. In addition to its limitations, this study has a number
of merits.
The participants that completed the study were among the few who originally
expressed interest that were able to successfully complete the week-long food diary. This
removed potential participants who would have been the least adherent. Additionally, a
majority of the participants were competitive strength, physique or combat athletes and had
experience with nutritional tracking and diet plans. We believe this, coupled with a non-
judgmental stance towards dietary mishaps and the encouragement of open communication,
lead to a high degree of adherence. Finally, while anthropometric equations carry inherent
error in regards to FFM changes, measurements of body mass and skinfold thickness when
not used in an equation are reliable (± 0.4mm technical error of measurement in this study).
From the findings it is suggested that during short-term, high caloric-deficit (40%)
diets, a high-protein (2.8g/kg) low-fat (mean 15.4% of calories) approach provides lower
ratings of athlete-specific stress, fatigue, mood disturbance and diet dissatisfaction than a
moderate-protein (1.6g/kg) moderate-fat (mean 36.5% of calories) approach. The finding of
diet dissatisfaction being higher during MPMF is novel, because even though protein's
satiating effect is documented (Leidy, Armstrong, Tang, Mattes, & Campbell, 2010), rarely is
it compared directly with fat. Rather, comparisons are typically made between carbohydrate
and fat (Cotton, Burley, Weststrate, & Blundell, 2007). However, the psychometric findings
cannot be attributed to satiety alone. The sole question related to nutrition appears on
DALDA part A, while DALDA part B and the POMS have no questions related to diet,
nutrition or hunger.
Fatigue sub-scale scores, TMDS and DALDA part B results indicate that athlete-
specific stress and fatigue were meaningfully higher during MPMF. At high protein intakes
as much as 60% of endogenous glucose production comes from gluconeogenesis
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
(Bilsborough & Mann, 2006; Linn et al., 2000). Thus, it is possible that the HPLF group
maintained higher levels of glycogen and had more readily available glucose, which could
have reduced athlete-specific ratings of stress and fatigue.
Neither changes in strength nor anthropometrics were meaningfully different between
diets. However, this is not entirely surprising given the length of this study, the fact that
neither diet provided a low protein intake and because both diets were matched for energy
and carbohydrate content. It is possible that had the diets lasted longer, the greater losses of
FFM during MPMF and the greater losses of strength during HPLF could have become
meaningful.
In terms of strength, there was a 19% chance that MPMF might prove to be a more
beneficial approach to maintenance of peak force than HPLF, while there was practically no
chance of the opposite. Intra-muscular fatty acid levels are replenished to a much lesser
degree when consuming 15% of calories from fat compared to 40% of calories from fat
(Boesch, Kreis, Hoppeler, Decombaz, & Fleith, 2000). Also, despite common perception that
carbohydrate alone fuels resistance training, intra-muscular triglyceride does contribute to
energy expended during heavy resistance exercise of relatively short duration in men (Essen-
Gustavsson & Tesch, 1990). Thus, it is possible that the low fat intake of 15% of calories in
HPLF may have impacted training in some of the participants in such a way that IMTP peak
force was negatively affected.
Future research should examine if body composition is an independent factor that
exacerbates the effects of dieting and to what magnitude. Also, longer periods of energy
restriction may have significantly different ramifications than short-term diets and thus
warrant study. Finally, study of female athletes during caloric restriction is lacking in
comparison to their male counter parts and requires investigation.
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Acknowledgements
ERH conceptualized the study, determined the methods, recruited the participants, developed
the diet plans, collected performance and psychometric data, analyzed the results, and wrote
the manuscript. CZ assisted in conceptualizing the study, aided in diet plan development,
communicated with participants regarding dietary matters, retained the blinding key and
edited all parts of the manuscript. DSR assisted in conceptualizing the study and provided
input on nutritional control, blinding and protein supplementation. RN collected
anthropometric data and assisted with recruitment. JC assisted in conceptualizing the study
and edited all parts of the manuscript. The authors would like to thank Cliff Harvey and
NuZest for providing their product at a greatly reduced cost. Additionally, we would like to
acknowledge Seth Lenetsky for assisting in compiling data, Barbara Lyon for mixing
powders and Professor Will Hopkins for his statistical guidance. Finally, we wish to sincerely
thank the volunteers for undergoing such dietary interventions in order to help inform
knowledge and practice in this field. There was no external financial support for this project.
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
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High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
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High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
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High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet
During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Table 1. Pre-dietary intervention participant characteristics (n = 13)
Characteristic
HPLF
MPMF
Age (yr)
27.4 ± 7.9
27.4 ± 7.9
Height (cm)
177.9 ± 10.4
177.9 ± 10.4
Weight (kg)
80.6 ± 8.4
80.7 ± 8.0
BMI (kg/m2)
25.5 ± 1.7
25.5 ± 1.6
Sum of Eight Skinfolds (mm)a
71.7 ± 18.3
76.7 ± 21.0
Body Fat Percentage (%) (Durnin & Womersley,
1974)
13.2 ± 4.2
14.1 ± 3.7
FFM (kg) (Durnin & Womersley, 1974)
70.0 ± 8.0
69.3 ± 7.5
Values are means ± SD.
HPLF, high-protein low-fat; MPMF, moderate-protein moderate-fat; BMI, body mass
index; FFM, fat free mass.
a Triceps, subscapular, biceps, iliac crest, supraspinale, abdominal, front thigh and
medial calf skinfolds.
Table 2. Nutritional profiles of dietary interventions
Intervention development
HPLF
MPMF
Protein (g/kg)
2.8
1.6
Carbohydrate (% of total calories)
35%
35%
Fat
remaining
remaining
Calories
60% habitual intake
60% habitual intake
Total intakes (meal plans plus
powders)
HPLF
MPMF
Protein (g/day)
225.7 ± 24.5
129.0 ± 14.0
Carbohydrate (g/day)
159.5 ± 21.9
159.5 ± 21.9
Fat (g/day)
31.4 ± 14.2
74.2 ± 15.0
Calories (kcal/day)
1829.3 ± 248.3
1829.3 ± 248.3
Intakes from meal plans alone
HPLF
MPMF
Protein (g/day)
115.3 ± 24.5
108.8 ± 14.0
Carbohydrate (g/day)
151.8 ± 21.9
64.1 ± 21.9
Fat (g/day)
29.7 ± 14.2
73.9 ± 15.0
Calories (kcal/day)
1341.6 ± 248.3
1364.0 ± 248.3
Intakes from supplement powders
alone
HPLF
MPMF
Protein (g/day)
110.4
20.2
Carbohydrate (g/day)
7.7
95.4
Fat (g/day)
1.7
0.3
Calories (kcal/day)
487.7
465.3
High-Protein Low-Fat Short-Term Diet Results in Less Stress and Fatigue Than Moderate-Protein Moderate-Fat Diet During Weight Loss in Male Weightlifters, A Pilot Study” by Helms ER
et al.
International Journal of Sport Nutrition and Exercise Metabolism
© 2014 Human Kinetics, Inc.
Table 3. Effects of dietary interventions
Measure
HPLF mean change
± 90% CL (%)
MPMF mean change
± 90% CL (%)
Chances that true effect of MPMF relative to HPLF are
substantially...
Qualitative assessment
of MPMF's effect
compared to HPLF's
effect
Harmful (%)
Trivial (%)
Beneficial (%)
Anthropometric
Bodyweight
-3.6 ± 0.6
-4.2 ± 0.6
<0.1
99
<0.1
Almost certainly trivial
Sum of eight skinfolds
-12.5 ± 3.4
-12.6 ± 3.5
2
97
1
Very likely trivial
FFM (Durnin & Womersley, 1974)
-2.1 ± 0.7
-2.5 ± 0.6
<0.1
99
<0.1
Almost certainly trivial
FFM (Yuhasz, 1974)
-2.9 ± 0.6
-3.3 ± 0.6
<0.1
99
<0.1
Almost certainly trivial
FFM (Peterson et al., 2003)
-2.1 ± 0.6
-2.5 ± 0.6
<0.1
99
<0.1
Almost certainly trivial
Performance
IMTP
-2.5 ± 1.4
-0.4 ± 3.5
<0.1
81
19
Likely trivial
Psychometric
HPLF mean ± 90%
CL
MPMF mean ± 90%
CL
DALDA "worse than normal" score
-
-
-
-
-
-
Part A total
16.7 ± 6.3
28.8 ± 10.8
83
17
<0.1
Likely harmful
Part B total
37.3 ± 16.7
66.0 ± 22.2
86
14
<0.1
Likely harmful
Part A "diet"
4.9 ± 1.9
7.5 ± 2.1
95
5
<0.1
Likely harmful
POMS average TMDS
0.7 ± 4.1
6.5 ± 6.5
75
25
<0.1
Possibly harmful
POMS average fatigue score
2.8 ± 1.5
4.7 ± 2.1
81
18
1
Likely harmful
HPLF, high-protein low-fat; MPMF, moderate-protein moderate-fat; CL, confidence limits; FFM, fat free mass; IMTP, isometric mid-thigh pull; DALDA, daily analysis of
life demands of athletes; POMS, profile of mood states; TMDS, total mood disturbance score
Qualitative assessment was determined as follows: <1%, almost certainly not; 1-5%, very unlikely; 5-25% unlikely; 25-75% possibly; 75-95%, likely, 95-99%, very likely;
>99%, almost certainly.
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