Immediate Effects of Brief Exposure to the Healthy Eating Plate on Adults’ Nutrition Knowledge: A Cross-Sectional Survey

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the opportunity to review this paper. The authors describe the evaluation of a education to improve healthy eating knowledge. There are several areas that require clarification before publication.

1. The sample self rated knowledge of healthy eating. The limitation of this approach is they do not know what they do not know. This is reflected in only 6.5% saying they had poor / very poor knowledge. Given this I would like to see the distribution of scores at baseline according to self rated knowledge in table 1 also
2. line 172-4 -Can you clarify 37% had used dietetic services - what for ?
3. Can you please combine the pre - post test results in one table to enable better comparison of scores and the changes in categories . the current arragement makes it hard to read this easily.
4. Table 4 and 5 are not easily interpreted esp if viewed in black and white. This table needs to include the actual correlation coefficienct value and p value as is the covention.  In the current form it is not very helpful to assit with interpretation of findings
5. RE the discussion - while knowledge has improved - we know that this does not always translate to behaviour change. Please include attention to this in the limitations
6. The last 4 lines of the discussion contain detail describing how to write a discussion - please remove
7. The conclusion is not written in a typical format and needs major revison. Please offer suggestions on the value of the work and next steps  not restate the findings

Author Response

Dear Reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

1. The sample self rated knowledge of healthy eating. The limitation of this approach is they do not know what they do not know. This is reflected in only 6.5% saying they had poor / very poor knowledge. Given this I would like to see the distribution of scores at baseline according to self rated knowledge in table 1 also
   
   Thank you for your suggestion. A statistically significant correlation was found between the level of knowledge in the pre-test and the prior self-assessment of knowledge about the principles of healthy eating (p<0.05). This means that the respondents were largely able to accurately assess their level of knowledge. This information is presented in Table 2 and the change has been made in the text. We did not add the distribution of self-assessment results to Table 1 because it has already been modified based on your other suggestion, i.e., we combined the pretest and posttest results.

2. line 172-4 -Can you clarify 37% had used dietetic services - what for ?
   
   Thank you for your question. The survey did not include a question about the purpose for which the respondents used dietary advice.
3. Can you please combine the pre - post test results in one table to enable better comparison of scores and the changes in categories . the current arragement makes it hard to read this easily.
   
   Thank you for your suggestion. The tables with the results have been combined.
   
   
4. Table 4 and 5 are not easily interpreted esp if viewed in black and white. This table needs to include the actual correlation coefficienct value and p value as is the covention.  In the current form it is not very helpful to assit with interpretation of findings.
   
   Thank you for your suggestion. The tables have been corrected.
   
   
5. RE the discussion - while knowledge has improved - we know that this does not always translate to behaviour change. Please include attention to this in the limitations

Thank you for your comment. It has been included.

6. The last 4 lines of the discussion contain detail describing how to write a discussion - please remove.
   
   Thank you for your suggestions. The sentences have been removed.
   
   
7. The conclusion is not written in a typical format and needs major revison. Please offer suggestions on the value of the work and next steps  not restate the findings.
   
   Thank you for your suggestion. The conclusion has been corrected.

 

Best regards

Authors

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

The title should be revised to reflect that this is an immediate knowledge test rather than a true pre–post intervention, for example by clarifying that the posttest was administered directly after a short exposure and not after any follow-up period.

The abstract should explicitly state that the study measures short-term recall and comprehension, not learning retention or behavioral impact, to avoid overstating the educational effect.

The study design should be described more precisely as a one-group pretest–posttest design without a control group, and the authors should acknowledge that causal claims about effectiveness cannot be made.

The Methods section would benefit from a clearer justification of the sample size, including whether any power calculation was performed to determine that 200 participants were sufficient.

The authors should explain how the questionnaire was developed and validated, including whether items were pretested, reviewed by experts, or assessed for reliability.

It would strengthen the paper to report internal consistency for the knowledge index (e.g., Cronbach’s alpha) rather than treating the index only as a simple percentage score.

The large reliance on true/false questions in the posttest should be discussed more critically, as this format increases the probability of correct guessing and may artificially inflate knowledge gains.

The authors should clarify whether the pretest and posttest were matched in difficulty, since several posttest items appear more concrete and directive than the pretest ones.

The five-minute exposure should be framed as a limitation, and the authors should avoid implying that such a brief contact can translate into meaningful long-term knowledge or behavior change.

The exclusion criterion based on viewing time (less than one minute) should be justified more clearly, including how many respondents were removed and whether this introduced selection bias.

The Results section should report confidence intervals for all key proportions and not only for the overall knowledge index.

The interpretation of “equalisation” across demographic groups should be softened, as the absence of statistical significance does not necessarily imply equivalence.

The persistent misunderstanding of the “balanced meal” concept should be discussed as a core design weakness of the Healthy Eating Plate rather than as a limitation of the test question alone.

The open-ended results suggest design and content issues, yet these are treated as marginal; the authors should integrate these qualitative findings more seriously into the discussion.

The Discussion should avoid repeating results in narrative form and instead focus more strongly on interpretation, mechanisms, and implications for public health practice.

The manuscript would benefit from a short comparison with similar evaluations of national food guides beyond MyPlate, to better situate the Polish model internationally.

The Conclusions section should be rewritten to be less promotional and more critical, especially regarding claims of effectiveness and universality.

Finally, the paper would be substantially strengthened by a statement outlining how the Healthy Eating Plate could be modified in response to the study’s weakest knowledge areas, particularly the balanced-meal message.

Author Response

Dear Reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

1. The title should be revised to reflect that this is an immediate knowledge test rather than a true pre–post intervention, for example by clarifying that the posttest was administered directly after a short exposure and not after any follow-up period.
   
   Thank you for your suggestions. The title has been changed to reflect the fact that this is an immediate knowledge test.
   
   
2. The abstract should explicitly state that the study measures short-term recall and comprehension, not learning retention or behavioral impact, to avoid overstating the educational effect.
   
   Thank you for your suggestion. The abstract has been corrected. It now states that the study concerns short-term memory and comprehension, rather than knowledge retention or behavioral impact.
   
   
3. The study design should be described more precisely as a one-group pretest–posttest design without a control group, and the authors should acknowledge that causal claims about effectiveness cannot be made.
   
   Thank you for your comment. We have described the study design in more detail in the materials and methods section. In addition, we have added a flowchart to clarify the study process. In the limitations section, we have added a more detailed description of the intervention effect, emphasizing that the outcome is a change in knowledge rather than eating behaviors.

4. The Methods section would benefit from a clearer justification of the sample size, including whether any power calculation was performed to determine that 200 participants were sufficient.
   
   Thank you for this suggestion. We agree that the rationale for the sample size should be stated more explicitly. This study was designed as a pragmatic, pre–post evaluation of immediate knowledge transfer under brief-exposure conditions rather than as a confirmatory trial of effectiveness. Therefore, we did not perform an a priori power calculation aimed at detecting a predefined minimal clinically important difference. Instead, the target sample size (n = 200) was set to (i) enable stable estimation of pre–post changes and item-level proportions, and (ii) support planned descriptive comparisons across key sociodemographic strata (sex, age group, education level, and residence type), while remaining feasible within the panel-based fieldwork. To make this transparent, we have added a justification in the Methods section explaining that the sample size was chosen for precision and feasibility. Specifically, for item-level proportions, a sample of 200 yields an approximate maximum 95% margin of error of about ±7 percentage points (at p = 0.50), which we considered acceptable for an initial evaluation of comprehension and short-term recall. We also clarify that the within-subject (paired) design increases statistical efficiency relative to between-group designs for detecting short-term change.

5. The authors should explain how the questionnaire was developed and validated, including whether items were pretested, reviewed by experts, or assessed for reliability.
   
   Thank you for this important comment. We agree that the manuscript should more clearly describe how the questionnaire was developed and what steps were taken to ensure validity. We have therefore expanded the Methods section to explain the item-development process and quality assurance. Briefly, the questionnaire was developed by the authors to assess immediate knowledge transfer related to the Healthy Eating Plate. Items were mapped to the educational content, and the instrument was internally reviewed by a multidisciplinary team (dietitians, a psychodietitian, a psychologist, and a psychologist) to assess clarity, relevance, and consistency with the intended constructs (face and content validity). In addition, part of the questionnaire was adapted from the validated KomPAN questionnaire, which has been used previously in Polish populations. We also clarify that no pilot testing was conducted prior to fieldwork; this is now acknowledged as a limitation, and we indicate that future research should include cognitive interviewing and formal psychometric evaluation (e.g., test–retest reliability and item analysis) in independent samples.

6. It would strengthen the paper to report internal consistency for the knowledge index (e.g., Cronbach’s alpha) rather than treating the index only as a simple percentage score.
   
   Thank you for this suggestion. We agree that some information on measurement reliability can be informative. However, we would like to clarify that the “knowledge index” in our study is a criterion-referenced, multi-domain knowledge test (items intentionally sample different guideline components) rather than a unidimensional psychometric scale. In such instruments, high internal consistency is not necessarily expected, and Cronbach’s alpha may underestimate quality or be difficult to interpret because it reflects item intercorrelation rather than content coverage.

7. The large reliance on true/false questions in the posttest should be discussed more critically, as this format increases the probability of correct guessing and may artificially inflate knowledge gains.
   
   Thank you for this important point. We agree that the true/false format increases the probability of correct responses due to guessing (chance level 50%) and may therefore inflate apparent posttest performance and pre–post gains, particularly if the pretest used more complex item formats. We have revised the Limitations section to discuss this explicitly and more critically, clarifying that the observed improvements should be interpreted as short-term knowledge transfer under a low-burden measurement approach rather than as definitive evidence of effectiveness. In addition, we have added a sensitivity statement noting that the posttest’s true/false structure may systematically bias results upward, and we outline in Future Work that subsequent evaluations should use more discriminating formats (e.g., multiple-choice with ≥4 options, scenario-based items, or open-ended responses) and, ideally, equivalent-form tests matched for difficulty.

8. The authors should clarify whether the pretest and posttest were matched in difficulty, since several posttest items appear more concrete and directive than the pretest ones.
   
   Thank you for your comment. The issue of potentially unequal difficulty levels between the pretest and posttest has been addressed in the limitations section.

9. The five-minute exposure should be framed as a limitation, and the authors should avoid implying that such a brief contact can translate into meaningful long-term knowledge or behavior change.
   
   Thank you for your suggestion. This has been included in the first paragraph of limitations.

10. The exclusion criterion based on viewing time (less than one minute) should be justified more clearly, including how many respondents were removed and whether this introduced selection bias.
    
    Thank you for your comment. It has been included.

11. The Results section should report confidence intervals for all key proportions and not only for the overall knowledge index.
    
    Thank you for your comment. It has been included in Table 1.

12. The interpretation of “equalisation” across demographic groups should be softened, as the absence of statistical significance does not necessarily imply equivalence.
    
    Thank you for your suggestion, It has been softened.

13. The persistent misunderstanding of the “balanced meal” concept should be discussed as a core design weakness of the Healthy Eating Plate rather than as a limitation of the test question alone.
    
    Thank you for this comment. In the Discussion, when addressing this item, we already outlined two plausible explanations for the observed pattern: (1) the relatively higher difficulty of the question itself, and (2) a potential limitation of the Healthy Eating Plate model in conveying this specific concept. To make it clearer that the underlying cause may also lie in the structure of the plate graphic, in line with the Reviewer’s suggestion we have revised the wording and added the phrase “design weakness.”

14. The open-ended results suggest design and content issues, yet these are treated as marginal; the authors should integrate these qualitative findings more seriously into the discussion.
    
    Thank you for your comment. It has been added.

15. The Discussion should avoid repeating results in narrative form and instead focus more strongly on interpretation, mechanisms, and implications for public health practice.
    
    Thank you for your comment. The Discussion has been improved.

17. The manuscript would benefit from a short comparison with similar evaluations of national food guides beyond MyPlate, to better situate the Polish model internationally.
    
    Thank you for this suggestion. We agree that a brief comparison with evaluations of national food guides beyond MyPlate would help situate the Polish model in a broader international context. However, when revising the manuscript we found that the available literature provides limited evidence specifically on the educational effectiveness of plate-based or graphic national food guides (i.e., short-term knowledge transfer and comprehension outcomes) comparable to our study design. Much of the existing work on national dietary guidelines focuses instead on associations with dietary intake patterns or broader health outcomes, which is outside the scope of the present paper. Among the few guides with relatively more published evaluation work directly relevant to comprehension/knowledge outcomes, MyPlate remains the most consistently examined, which is why we used it as the primary reference point.
18. The Conclusions section should be rewritten to be less promotional and more critical, especially regarding claims of effectiveness and universality.
    
    Thank you for your suggestion. The conclusion has been corrected.
    
    
19. Finally, the paper would be substantially strengthened by a statement outlining how the Healthy Eating Plate could be modified in response to the study’s weakest knowledge areas, particularly the balanced-meal message.
    
    Thank you for your comment. It has been added to the conclusion section.

Best regards

Authors

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the modifications. i still would like the ACTUAL correlation coefficient to be included in each box of contigency matrices. i am interested to know if the correlation coefficients of both the signfincant correlations and non significant ones 

Author Response

Dear Reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

1. Thank you for the modifications. i still would like the ACTUAL correlation coefficient to be included in each box of contigency matrices. i am interested to know if the correlation coefficients of both the signfincant correlations and non significant ones.

 

Thank you very much for your comment. The actual correlation coefficient was taken into account in each field of the contingency matrices, both for significant and insignificant correlations (Table 2 and Table 3).

Best regards

Authors

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript is well structured and presents clear objectives with robust statistical reporting (e.g., paired t-test with effect size d = 0.86), but it requires further methodological clarification before publication. Specifically, the absence of a control group, the use of predominantly true/false items in the posttest (which increases guessing probability to 50%), and the lack of reported reliability indicators such as Cronbach’s alpha should be more explicitly addressed to strengthen internal validity and reviewer confidence.

Author Response

Dear Reviewer,

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

1. The manuscript is well structured and presents clear objectives with robust statistical reporting (e.g., paired t-test with effect size d = 0.86), but it requires further methodological clarification before publication. Specifically, the absence of a control group, the use of predominantly true/false items in the posttest (which increases guessing probability to 50%), and the lack of reported reliability indicators such as Cronbach’s alpha should be more explicitly addressed to strengthen internal validity and reviewer confidence.

Thank you for your comment. All comments have been taken into account and added to the Materials and Methods section.

 

Best regards

Authors