The Role of Whey Protein in Maintaining Fat-Free Mass and Promoting Fat Loss After 18 Months of Bariatric Surgery

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this manuscript. The study addresses an important and timely topic in the field of bariatric surgery and postoperative nutritional management. I commend the authors for their work and offer the following major revisions aimed at strengthening the clarity, rigor, and impact of the manuscript.

Insufficient Intervention Duration: The 4-week supplementation period may be too short to yield meaningful changes in muscle function or performance indicators such as handgrip strength or gait speed. The authors should either (a) justify the rationale for selecting this duration more convincingly, or (b) acknowledge this limitation more explicitly in the discussion.

Lack of Power Analysis: The manuscript does not report a sample size calculation or power analysis. Given the relatively small number of participants (n=43), it is essential to address whether the study was adequately powered to detect statistically and clinically relevant differences between groups.

Placebo Description and Blinding: More detailed information is needed regarding the composition and sensory characteristics of the maltodextrin placebo. Were the energy values and appearance/flavor matched? This is critical to validate the blinding process.

Physical Activity Monitoring: While physical activity was monitored via self-report, this approach may introduce bias. The authors are encouraged to acknowledge the limitations of relying on self-reported data and discuss its potential impact on the outcomes.

Ultrasound Methodology Clarification: Further information should be provided on the ultrasound assessments—specifically, who performed the measurements, whether the assessor was blinded to group allocation, and any measures taken to ensure intra- and inter-rater reliability.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I thank the authors of the manuscript "The Role of Whey Protein in Maintaining Fat-Free Mass and Promoting Fat Loss After 18 Months of Bariatric Surgery" for the time they have devoted to conducting their research project and for the time they have devoted to writing their manuscript. This study aims to evaluate whether whey protein supplementation improves weight loss and body composition in women undergoing medium-term post-operatory. The manuscript deals with a topical issue of interest to the scientific community. The introduction section is intended to introduce the topic of the study. The methods section describes the methodology used to conduct the study. The results section gives clear and easy to read data obtained from authors, both as a descriptive part in the text and as data reported in tables. The discussion sections contain a description of data in literature compared with results obtained by authors. The conclusions are relevant to the results obtained.

Even in the editorial form, the manuscript contains very few errors.

I ask the authors to always report in the same way, in a uniform and standardized way, the various information in the manuscript. For example, currently in the manuscript is reported MD group, Malto group, etc. (among other things, nowhere in the manuscript has it been reported that MD stands for maltodextrin).

Lines 34, 42, 121, 125, 141, 161, 182: I ask the authors to correct the spacing after the point.

Lines 75, 137, 143, 144, 154, 223: I ask the authors to correct the spacing between the number and the unit of measurement (give a space, 30 g).

Line 120: I ask the authors to correct the "p" of the p-value. Such a "p" is always written in lower case. 

Researchers are reminded that scales with built-in stadiometer are not in line with anthropometric standards (Reference Manual for Anthropometric Standardization, Timothy G. Lohman et al.), therefore the use of such instrumentation should be reported within the study boundaries as height is not measured in a standardised manner according to international procedures.

Table 2: This table shows the same data on the triceps fold twice. The numbers in the Whey T0 column are not all perfectly aligned. I ask the authors to report precisely the statistically significant differences (p), since they only inserted the symbol "*", but the numerical value is missing. I ask the authors to improve this table. 

Table 3: This table lacks legend, values expressed p value. I ask the authors to better arrange this table. 

References: The reference consists of 22 bibliographic entries. It could be increased since there is a lot of material on this subject in the literature. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Review of “The Role of Whey Protein in Maintaining Fat-Free Mass and Promoting Fat Loss After 18 Months of Bariatric Surgery”

 

• This is a matched-group non-randomized clinical trial. Authors must acknowledge this as an important limitation in the discussion section, given that randomized trials are better at determining if an intervention is superior to another. 

• It studied post-bariatric patients (after 18 months). I believe the introduction must be improved in order to specify why this specific group is worth studying.
• Abstract, results: please, include some numbers in the abstract, that is, results must have means and standard deviation of the main outcomes of the study.
• Authors should follow the JBI checklist for quasi- experimental studies; 
• The main limitation of the study, that prevents me from going further in the review, is the inadequate statistical analysis. Clinical trials must be analyzed considering the interaction between group and moment of measure. paired sample t test is simple useless in the context. There are several texts available that explain why running 2  unpaired t test and comparing the pvalues between groups is inadequate, I refer the authros to 2 different papers published in BMJ by Doug Altman in 1996 and 2001 (https://pubmed.ncbi.nlm.nih.gov/8842080/ and https://pubmed.ncbi.nlm.nih.gov/11701584/). At minimum, authors should run an ANCOVA using the baseline values of the outcome as covariates in the model, where group is a fixed factor.

- authors should discuss the fact that protein intake did not change between groups, even with the supplementation;

- authors must include a flowdiagram of participant selection and explain if there were dropouts and how many individuals were approached, how many were included etc.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have answered to all my comments

Reviewer 3 Report

Comments and Suggestions for Authors

The authors improved the statistical analysis and the findings are now presented in a correct way.