Coffee Intake Reduces Short-Term Carbohydrate and Lipid Consumption
, Ioannis Vlastos 2, Kalliopi Gkouskou 3, Efstathios Skoufas 1,4,* and Dimitrios Chaniotis 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for the opportunity to review the manuscript by Lazou and colleagues. It is an interesting study. Please consider my recommendations for improvement below.
I do not think it is appropriate to state or imply that caffeine is responsible for effects observed. The control trial consumed water, and there is more to coffee than caffeine. Therefore, coffee resulted in altered food intake.
It seems the control trial is a weakness of the study. My opinion is that decaffeinated coffee would have been more optimal since it would have allowed for specifically comparing the effects of caffeine and, more importantly, it would have made blinding possible. I welcome the authors perspective on this.
A limitations section is needed. This would include addressing the weakness of the control trial and the lack of blinding in the study.
Was a sample size estimation performed before the study? If not, the authors should perform a post hoc power analysis.
It is critical to include participant characteristics, ideally as a table.
Given that this is a brief report, I think the Introduction and Discussion sections are much too long. They should be shortened to match the length of the methods and results sections.
The Methods section includes too much superfluous language, such as "carefully and deliberately", "strategically", "explicitly", "meticulously", etc. These terms are not needed. Please simplify wording to make it smoother for readers.
Line 112: Normal weight BMI is 18.5-24.9 kg/m2, not <25 kg/m2
How is it that participants consumed 200 mL of coffee and this was precisely 5 mg of caffeine per kg of body weight? Did all participants weigh the exact same?
Table 1: The degree of specificity (i.e., number of decimal points) should be consistent between the mean and SDs.
Author Response
Authors’ reply to 1st Reviewer’s comments
1st Comment: “I do not think it is appropriate to state or imply that caffeine is responsible for effects observed. The control trial consumed water, and there is more to coffee than caffeine. Therefore, coffee resulted in altered food intake.”
Author’s reply: We agree with the comment. We acknowledge that coffee contains multiple bioactive compounds beyond caffeine, which may influence food consumption. In that context, we proceeded, when needed it, with replacing the term “caffeine” with “caffeinated coffee” or “coffee consumption” all over the manuscript. The replacements can be found in the track changes manuscript. We have, also, added this as a limitation in the discussion section (p. 6 lines: 246-255 of the track-changes manuscript).
2nd Comment: “It seems the control trial is a weakness of the study. My opinion is that decaffeinated coffee would have been more optimal since it would have allowed for specifically comparing the effects of caffeine and, more importantly, it would have made blinding possible. I welcome the authors perspective on this.”
Author’s reply: We thank the reviewer for the comment. Indeed, a design with the use of decaffeinated coffee beverage would promote both the examination of caffeine’s effect and the blindness of the design. Nevertheless, the use of water was more suitable for practical reasons at the moment of the study. In any case, we have mentioned this as a limitation in the discussion section (p. 6 lines: 246-255 of the track-changes manuscript).
3rd Comment: “A limitations section is needed. This would include addressing the weakness of the control trial and the lack of blinding in the study.”
Author’s reply: A limitation section has been added in discussion, as recommended (p. 6 lines: 245-272 of the track-changes manuscript)
4th Comment: “Was a sample size estimation performed before the study? If not, the authors should perform a post hoc power analysis?”
Author’s reply: We have to admit that the study did not perform an a priori sample size estimation to determine the minimum number of participants required to detect significant differences between the caffeine and control conditions. We, therefore, conducted the recommended post hoc analysis by calculating Cohen’s d. We have added the statistical post hoc power analysis in Table 2. Since, the results of the post hoc analysis were not optimum, we added this as a limitation in the discussion section (p. 6 lines: 259-263 of the track-changes manuscript).
5th Comment: “It is critical to include participant characteristics, ideally as a table.”
Author’s reply: A table summarizing participant characteristics (age, BMI, gender) has been added (p. 4 of the track-changes manuscript).
6th Comment: “Given that this is a brief report, I think the Introduction and Discussion sections are much too long. They should be shortened to match the length of the methods and results sections.”
Author’s reply: We thank the reviewer for the comment. The truth is that the first submission was in the type of a brief report. Nevertheless, the journal’s editing team asked us to submit it as a full paper. In that context, we had to increase the wordcount in introduction and discussion.
7th Comment: “The Methods section includes too much superfluous language, such as "carefully and deliberately", "strategically", "explicitly", "meticulously", etc. These terms are not needed. Please simplify wording to make it smoother for readers.”
Author’s reply: We agree with the reviewer’s comment as for the superfluous language. Thus, we removed unnecessary adjectives and simplified the methodology section.
8th Comment: “Line 112: Normal weight BMI is 18.5-24.9 kg/m2, not <25 kg/m2”
Author’s reply: We thank the reviewer for pointing out this. We have corrected and added the correct range for normal weight as for BMI (p. 4 lines: 176 of the track-changes manuscript ).
9th Comment: “How is it that participants consumed 200 mL of coffee and this was precisely 5 mg of caffeine per kg of body weight? Did all participants weigh the exact same?”
Author’s reply: We appreciate the reviewer for the comment. Fortunately, the reviewer has noticed this inconsistency! Apparently, the 5mg of caffeine is referred to its content in the instant coffee beverage. Thus, we have deleted the typo (p.3 lines: 138 of the track-changes manuscript ).
10th Comment: “Table 1: The degree of specificity (i.e., number of decimal points) should be consistent between the mean and SDs.”
Author’s reply: We agree with the reviewer. Thus we have changed the number of decimal points, so as to be consistent between mean and SDs values.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe subject is very interesting, congratulations for the effort you had put on this experimental study. I sincerely hope that this is a pilot for further studies.
Introduction
Line 48, the abbreviation is inverted, first you put the full text and the abbreviation between brackets
Materials and Methods
The sample description would go better in results, in participants you can refer only to recruitment methods including the inclusion and exclusion criteria
I would suggest you to do a graphical abstract or a figure to present the experimental design
Lines 149 How much days did the participants log in the food diary?
Results
Lines163 to 169 would better be put in the end of the discussion, in the results section simply present the results
Do you have some sample characteristics data? You could present first the sample main features
Discussion
The discussion should be better supported with references , you have full paragraphs with no references (such as line 162 and beyond)
Author Response
Authors’ reply to 2nd Reviewer’s comments
1st Comment: “Line 48, the abbreviation is inverted, first you put the full text and the abbreviation between brackets.”
Author’s reply: We thank the reviewer for pointing out the misplaced abbreviation. Thus, we have corrected the abbreviation as Coronary Heart Disease (CHD) (p. 2 lines: 47 of the track-changes manuscript).
2nd Comment: “The sample description would go better in results, in participants you can refer only to recruitment methods including the inclusion and exclusion criteria.”
Author’s reply: We agree with reviewer’s comment. Therefore, we deleted the participants’ basic characteristics and presented them in results section (p. 4 lines: 172-176 of the track-changes manuscript).
3rd Comment: “I would suggest you to do a graphical abstract or a figure to present the experimental design.”
Author’s reply: We appreciate reviewer’s comment. Indeed, your suggestion to include a graphical abstract or flowchart of the experimental design would probably better visualize the experimental procedure. Nevertheless, we believe that the detailed text-written description in the section of Methodology communicates the experiment adequately. We hope this explanation is satisfactory, but we will welcome reconsidering if the editorial board feels strongly about including a figure.
4th Comment: “Lines 149 How much days did the participants log in the food diary?”
Author’s reply: We would like to thank the reviewer for the comment. Indeed, it is not clear how many days the participants recorded their food intake. In fact, the participants recorded their dietary intake for one full experimental day (starting after the lunch buffet until midnight), excluding any caffeine or caffeinated beverages. Thus, we added this information in the manuscript (p. 3 lines: 149-150 of the track-changes manuscript).
5th Comment: “Lines163 to 169 would better be put in the end of the discussion, in the results section simply present the results.”
Author’s reply: We agree with the reviewer’s comment. We have moved the result’s first paragraph at the first paragraph of the discussion section (p. 5 lines: 208-214 of the track-changes manuscript ).
6th Comment: “Do you have some sample characteristics data? You could present first the sample main features”
Author’s reply: We have added a description table as for the basic characteristics of the participants. Please see Table 1 (p. 5 of the track-changes manuscript).
7th Comment: “The discussion should be better supported with references , you have full paragraphs with no references (such as line 162 and beyond).”
Author’s reply: We thank the reviewer for recommending the addition of references in the discussion section. Thus, we proceeded with the addition of references in the discussion section.
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
I wish I had taken part in your experiment. Your study is well-planned and very interesting. Congratulations!
As for my minor suggestions:
1. Please check your manuscript for typos (I noticed a few unnecessary spaces);
2. Please add the name of the software used for the statistical analysis in paragraph 2.3;
3. Considering the rigorous protocol of the study, it is a pity that the number of male and female participants is not comparable.
Best regards,
The reviewer.
Author Response
Authors’ reply to 3rd Reviewer’s comments
1st Comment: “Please check your manuscript for typos (I noticed a few unnecessary spaces);”
Author’s reply: We thank the reviewer for their positive appraisal of our manuscript. As for the first comment, we made an extensive crosschecking for typos across the manuscript, and made few corrections. Nevertheless, you are welcome to point out if we missed any other typographic error.
2nd Comment: “Please add the name of the software used for the statistical analysis in paragraph 2.3;”
Author’s reply: We appreciate reviewer’s comment, and proceeded adding the name of the software analysis package (p. 4 lines: 162-163 of the track-changes manuscript).
3rd Comment: “Considering the rigorous protocol of the study, it is a pity that the number of male and female participants is not comparable.”
Author’s reply: We appreciate the reviewer’s observation regarding the gender imbalance in our study sample. We add this imbalance in the limitation section. (p. 6 lines: 256-259 of the track-changes manuscript).
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsI thank the authors for addressing my comments.
Reviewer 2 Report
Comments and Suggestions for AuthorsI appreciate the answers and the work done in the manuscript revision.
