Intermittent Energy Restriction Attenuates the Loss of Fat Free Mass in Resistance Trained Individuals. A Randomized Controlled Trial

Round 1

Reviewer 1 Report

The authors investigated body composition changes in RT-individuals during continuous energy restriction or intermittent restriction. The authors concluded that a preservation of fat-free mass and resting metabolic rate in response to a two-day carbohydrate refeed during an energy restricted diet in lean, resistance trained males and females.

The manuscript is well written and present interesting findings. However, some modifications are required :

At the end of the introduction, I suggest adding some hypothesis based on the results of previous studies presented in this section.

Participants. Do the authors perform a power calculation to determine the required sample size. This information is important and should be added or discussed in a limitation part.

Statistical analysis. I suggest adding the calculation of the confidence interval and these values should be added in the results section.

Discussion. At the end of this section, I suggest adding the practical recommendations of the study.

Author Response

Reviewer #1

The manuscript is well written and present interesting findings. However, some modifications are required :

Thank you very much for the thorough review and constructive criticism of our first draft.  We have addressed each of your suggestions and recommendations.  Please see our responses below.

At the end of the introduction, I suggest adding some hypothesis based on the results of previous studies presented in this section.

We added the following hypothesis to the end of the introduction [lines 90 to 96].

Our hypothesis is that regardless of diet assignment (continuous energy restriction or intermittent restriction, muscle mass and resting metabolic rate will be maintained during the dietary intervention due to the inclusion of a resistance exercise stimulus and a relatively high dietary protein intake.  Due to a lack of existing research for including intermittent energy restriction in a resistance-trained lean population, we were unsure if positive body composition and resting metabolic rate outcomes would be observed.

Participants. Do the authors perform a power calculation to determine the required sample size. This information is important and should be added or discussed in a limitation part.

We added the following hypothesis to the beginning of section 2.2 [lines XX to XX].

Using data from a similar population in which lean athletes were under investigation for weight loss [1], the effect size calculated for a decrease in fat mass over a period of several months (using a caloric restriction of 20%) was 0.5. Using this calculated effect size, an alpha level of 0.05, and a power of 0.9, a sample size of approximately 12 subjects per group was estimated.

Statistical analysis. I suggest adding the calculation of the confidence interval and these values should be added in the results section.

We have added the 95% Confidence Interval data to Table 3.

Discussion. At the end of this section, I suggest adding the practical recommendations of the study.

We added the following hypothesis to the end of the Discussion section (section 4.0) [lines XX to XX]. The practical recommendations of the study are such that if a lean, resistance-trained individual seeks to reduce caloric intake for the purpose of fat loss, this should be undertaken with relatively high protein intakes, a slow rate of weight loss, and periodic carbohydrate refeeding. Such considerations appear to support the maintenance of fat-free mass and resting metabolic rate during caloric restriction.

Reviewer 2 Report

I commend the authors not only for a well written, clear manuscript, but also for such novel work. I have only minor comments.

Last paragraph of introduction “a twice-weekly carbohydrate refeed” is a little ambigious to me when I read it, I know it occurs twice per week, but it is a little unclear that these are refeed days. Perhaps reword to be “two days per week of carbohydrate refeeding” or something similar.

Line 109-110 Could you explain how sufficient compliance for inclusion was determined?

Line 116 please change “there were no differences between groups” to “no significant” differences between groups, as Table 1 displays different means and standard deviations for each variable. Similarly, please make this change on lines 217, 223, 236

Line 129 Was the personal nutrition coach qualified in any way? If so please state.

Line 149 “as a supplemental files”, please remove “a” for grammar

Lines 154-155 how was low to moderate intensity defined or instructed?

Line 174 place “the” between “touching” and “side of the body”

Line 186-187 can you state how many of the subjects from each group were tested using the other metabolic cart? If there was not a reasonably even breakdown, did you perform any agreement testing between devices to ensure there wasn’t a systematic difference between the two which could have impacted the results? Not an issue if the split between groups was even-iso.

Line 191 “(2017 Colquhoun PMID = 28129275) “ is this the correct in-text citation format?

Line 242-244 I believe this was left over from a template for the author’s instructions, please delete (and no worries, I’ve done similar things myself previously)

Line 276 you state greater glycogen levels could have resulted in more training volume, yet in the results you state there were no significant differences in volume performed. Perhaps revise to less fatigue during training and subsequently greater effort or something similar.

Author Response

Reviewer #2

I commend the authors not only for a well written, clear manuscript, but also for such novel work. I have only minor comments.

Thank you very much for the kind words.  We also want to thank you for taking your valuable time to critique our first draft and provide valuable recommendations to improve our paper. Also, you were able to find several instances of oversights by our team (in spite of my personal reading over this at least 6 times!).  Thank you for taking the review process seriously and improving our work.

Last paragraph of introduction “a twice-weekly carbohydrate refeed” is a little ambigious to me when I read it, I know it occurs twice per week, but it is a little unclear that these are refeed days. Perhaps reword to be “two days per week of carbohydrate refeeding” or something similar.

This is much better phrasing of this sentence.  We edited this sentence exactly as you suggested. Refer to line 87.

Line 109-110 Could you explain how sufficient compliance for inclusion was determined?

These 3 subjects self-attested that they did not follow the prescribed diet (both in protein intake and caloric restriction). Line 124 has added in the words ‘self-admitted’ to make this more clear.

Line 116 please change “there were no differences between groups” to “no significant” differences between groups, as Table 1 displays different means and standard deviations for each variable. Similarly, please make this change on lines 217, 223, 236

We have made this change to each of the areas you suggested.  Refer to lines 130, 233, 239, and 252 for the current line numbers.

Line 129 Was the personal nutrition coach qualified in any way? If so please state.

Our nutrition coaches were not registered dieticians.  Each nutrition coach had coaching experience in assisting clients with macronutrient based calculations, and all had college coursework in nutrition (with most having graduate coursework in nutrition as well). 

Line 149 “as a supplemental files”, please remove “a” for grammar

Thank you for catching this. This change was made.  It is now line 164.

Lines 154-155 how was low to moderate intensity defined or instructed?

The subjects were instructed to run or exercise at a pace that would allow them to have a conversation with running partner if they wanted to.  This was the only instruction given for this aspect of the aerobic training.  This language was added to line 170.

Line 174 place “the” between “touching” and “side of the body”

Line 186-187 can you state how many of the subjects from each group were tested using the other metabolic cart? If there was not a reasonably even breakdown, did you perform any agreement testing between devices to ensure there wasn’t a systematic difference between the two which could have impacted the results? Not an issue if the split between groups was even-iso.

This is line 202 now.  Of the 7 subjects that this effected, 5 were in the continuous group and 2 were in the refeed group).  This was not an equal allotment, but it could have also been worse.  In the past, I have conducted a handful (about 5) tests that directly compared the Parvo unit with the Cosmed unit.  The data that I generated was very good, but unfortunately I do not have specific records of these few tests.  In my professional opinion, I am confident that both units are sensitive enough to detect changes in RMR over time from a caloric-restricted diet.  To that note, I have published research using both units.  To be as transparent as possible with this issue, in addition to making it clear to the reader that we had this issue and that we brought in a separate machine, we have now added (refer to line 202) the number of subjects from both groups that were affected by this change.  Thank you for suggesting that we do this. 

Line 191 “(2017 Colquhoun PMID = 28129275) “ is this the correct in-text citation format?

Thank you for catching this.  This was a mistake.  We have corrected this with the appropriate citation.

Line 242-244 I believe this was left over from a template for the author’s instructions, please delete (and no worries, I’ve done similar things myself previously)

You are correct.  We accidentally left in the appendix instructions.  We have now deleted this information from the manuscript.  Please refer to lines 383-384.

Line 276 you state greater glycogen levels could have resulted in more training volume, yet in the results you state there were no significant differences in volume performed. Perhaps revise to less fatigue during training and subsequently greater effort or something similar.

Thank you for making this suggestion.  We have updated this section (refer to lines 296-297) with the following: “It could also be hypothesized that the twice-weekly increase in carbohydrate intake elevated skeletal muscle glycogen stores. Such increases may have resulted in less fatigue and subsequently greater effort during the workouts following the carbohydrate refeeds.”