Title: TITLE A randomized controlled trial to evaluate the acceptability and effectiveness of
two eating disorders prevention interventions: The HEIDI BP-HW project.
Version: 1 Date: 14 Jun 2023
Reviewer's report:
In this manuscript, the authors examined the acceptability of two eating disorder prevention
interventions  in a student population and compared their effectiveness to a waiting control
group. For this, the Body Project Intervention, a group program aiming at reducing maladaptive
beliefs about the body, shape and weight by creating a dissonance, and the Health Weight
Intervention, a program aiming at creating lifestyle changes, were adapted to the French-
speaking Swiss population. Both interventions were deemed acceptable. Additionally, the
authors found that body dissatisfaction, dietary restraint and shape concerns were reduced
with moderate to large effect sizes in both intervention groups compared to the control group
Unfortunately, recruitment problems only allowed to analyze the data of 33 participants.
The presented manuscript is a very clear and well-written manuscript enhancing our knowledge
on the acceptability and feasibility of group-based prevention programs. Moreover, the authors
adapted and provided two well-established interventions programs to the Swiss French-speaking
population possibly enhancing eating disorder prevention in this population. I appreciate the
transparency about the recruitment problems, the detailed preregistration, the publication of
a study protocol and the convincing RCT-study design. However, I do have some significant
revisions to suggest that might enhance the clarity of the present manuscript.
Major Concerns:
One important research question of the present study was to evaluate the acceptability of two
eating disorder prevention programs. Therefore, a subjective and an objective measurement
were combined to evaluate the satisfaction of the two interventions. While this procedure
enhances the validity of the presented results, the criterion of “50% of the participants attending
at least 3 sessions” for high acceptability was not pre-specified. At least, I could not find
any information on this criterion in the manuscript or the study protocol. Therefore, I think
it is important to provide a clear explanation on why this criterion was chosen and how it
reflects a high acceptability. Furthermore, given the low number of included participants and the
recruitment problems, one might conclude that the sample represents highly motivated students
possibly attending a higher number of sessions than participants in regular circumstances would.
Additionally, the lockdown and the associated reduction in social contacts might have further
increased motivation to attend the sessions, as they provided social contact with peers. In
my opinion, these limitations should be considered when discussion the acceptability of the
interventions.
My second major point concerns the presented data. The means for the BSQ-8C in the
three groups range from 26.3-30.5, with standard deviations ranging from 5.2-5.7. However,
according to the inclusion criteria participants were required to score at least with 26 on
the BSQ-8C. There might be a misconception on my part, but I wondered how these values
are possible, at least they seem to be unlikely. Please provide additional information on the
distribution and range of the body dissatisfaction values. Additionally, if the authors want to
support the current movement of open data, they could consider sharing anonymized data online.
Third, the authors label their study as a pilot study. While I understand that the recruitment
challenges caused by the pandemic hindered the ability to recruit the intended sample size, it
is important to note that the current study was not initially planned and preregistered as a pilot
study. Therefore, I think using the term pilot study might be misleading.
My next point refers to the inclusion and exclusion criteria. These criteria were sensibly chosen
and I am curious about how the absence of the exclusion criteria, specifically the diagnosis of
mood, anxiety and eating disorder, was determined. Was there a diagnostic interview conducted
for this purpose? If so, it would be helpful to provide more information about the diagnostic
procedure used and the qualifications of the interviewer. Additionally, I noticed that some of the
preregistered exclusion criteria were modified. It would be valuable to understand the reasons
behind these changes, including the timing during the recruitment process and whether any
potential participants were excluded based on the initial criteria before they were altered.
Most importantly, the data analyses reported need some revision:
- I would appreciate a more detailed explanation on why the authors focused on the per-protocol
analysis and included only participants that completed all assessments. In my opinion, it might
be helpful to include as much data as possible given the low number of participants.
- The study protocol claims that an analysis of variance (ANCOVA) was planned for the study.
However, the authors conducted Wilcoxon tests on the difference values. I understand that
the challenging recruitment conditions might not have allowed to follow the preregistered data
analyses. However, in my opinion, discussing the appropriateness of the analyses performed
and clarifying why they deviated from the preregistered analysis plan is necessary. As there
are discussions on the reliability of difference scores, clarifying why these analyses were more
appropriate (if they were) than the ones preregistered would allow for a better evaluation of
the validity of the presented analyses. Alternatively, the results of the preregistered analyses
could be reported in a supplement. In this manner, I wonder why the authors did not include any
within-group pre-post analyses, as the study was initially powered for these comparisons.
- Wilcoxon rank tests were conducted as significance test to analyze the stability of the
intervention effects. To my knowledge, analyses including all three measurements would
yield more statistical power. Thus, I questioned why the authors did not include all three
assessments. However, if only the post-assessment and follow-up analyses are considered,
equivalence tests might be more suitable (see for example: https://www.ncbi.nlm.nih.gov/pmc/
articles/PMC5502906/). The conducted significance test are normally used to find differences
not to test their absence.
- Overall, I would appreciate a more extensive explanation on why the presented analyses
methods were used.
My next concern relates to the interesting analyses on the feasibility. The authors evaluated
the feasibility of the applied interventions based on the participants that did not start the
intervention after being randomized. I think it would be beneficial to add the information that
a high percentage (20%) of eligible subjects declined to participate before being randomized.
Do the authors have any data on these subjects and their reasons for not participating? Including
such information would provide valuable insights into factors influencing participation and help
understanding the feasibility of the two interventions.
Lastly, the authors transparently discussed the small sample size and recruitment problems
in their discussion section. However, I think it would be important to consistently stress the
impact of the small sample size and the potential influence of individual participants throughout
the discussion. In my opinion, the authors should only cautiously derive conclusions from the
presented results considering the small sample size. Moreover, the authors should be careful
when discussing differences in the effects between the Body Project (BP) and Health Weight
(HW) groups, as no statistical analysis was conducted to compare these effects (for more
information why this might be problematic, see Makin & Orban de Xivry (2019): https://
elifesciences.org/articles/48175). Additionally, the authors could provide a more elaborate
discussion on potential limitations influencing the outcomes.
Additional minor aspects:
- The trial registration at ClinicalTrials is a major advantage of the present study. However, there
seems to be an inconsistency between the number of included participants on ClinicalTrials (42)
and the manuscript (40). Please clarify this discrepancy.
- The prevalence numbers retrieved from Mohler-Kuo et al. (2016) appear unusually high and I
could not find this specific number in the cited publication. It seems like the authors added the
prevalence rates for the different eating disorders to obtain one score. However, since individuals
might have fulfilled the diagnostic criteria for different eating disorders in their lifetime, adding
up the different prevalence rates might overestimate the true lifetime prevalence of eating
disorders. Please address this concern and provide clarification.
- In the method section, it would be helpful if the authors could provide more information on
the reliability and validity of the included questionnaires, for example by calculating reliably
indexes such as Cronbach’s alpha. This might be particularly important for the assessment of
satisfaction, as these items were specifically generated for the current study.
- The authors describe a blinded randomization process. Still, I am not quite sure how they
ensured that the first author was blind to the randomization. As the first author decided whether
interested subjects were included, a blinded procedure is particularly crucial.
- I am curious about the rationale behind originally restricting the age criterion from 18 to 25.
Were there any specific reasons for this age range?
- Conducting a power analysis is a crucial step in clinical research, and it is commendable that
the current study included one. Still, I wondered why the current study was powered for pre-
post effects even though the hypotheses and the presented statistical analyses include group
comparisons.
- When reporting the results of the group comparisons on page 18, it would be helpful to refer
to Table 3 in the text for better clarity and ease of reference.
- In the method section, the authors cite a website respectively provide a link to explain how
the reported effect sizes were interpreted. Please cite the original publication reported on the
linked website.
- I highly appreciate that the magnitudes of the effects found are reported in the abstract.
Nevertheless, it would be beneficial to additionally include effect sizes and p-values in the
abstract to provide a more comprehensive summary of the results.
- There is a typo in the manuscript, on page 6 it says “et” instead of “and”.
- Figure 2 still looks like an R output and the variable names of the data set are depicted. The
authors should consider updating the figure to provide a reader-friendly version.