Weight suppression, bingeing, and purging as predictors of weight gain during inpatient treatment in persons with bulimia nervosa

  1. Adrian Meule
  2. Anna Dieffenbacher
  3. David R. Kolar
  4. Ulrich Voderholzer

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Abstract

Objective: Patients with bulimia nervosa (BN) often gain weight during treatment, which potentially poses a threat to treatment adherence. Although weight suppression has been found to be a predictor of weight gain in persons with BN, research about the nature of weight changes during treatment and other predictors thereof is scarce.Method: The current study examined weight suppression as well as self-reported bingeing severity and purging frequency at admission as predictors of weight change during inpatient treatment in 746 persons with BN (95% female).Results: Body mass index (BMI) increased linearly across treatment weeks. Higher weight suppression predicted larger weight gain, particularly in those with a relatively low BMI at admission. More frequent purging and less severe bingeing predicted larger weight gain but high bingeing severity in combination with infrequent purging attenuated this effect.Conclusions: Results replicate that those with high weight suppression are at higher risk for gaining weight during BN treatment but extend these findings in that this effect additionally depends on current BMI, similar to findings reported in persons with anorexia nervosa. They further demonstrate that the core features of BN—bingeing and purging—also predict weight change both separately and interactively and may, therefore, be considered in psychoeducation and therapy planning.

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  1. PREreview

    This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/14917958.

    This study examined predictors of weight gain during inpatient treatment for bulimia nervosa. Higher weight suppression predicted greater weight gain, particularly in those with lower BMI at admission. Unlike previous research, this study also explored the role of bingeing and purging in weight changes. Findings showed that more frequent purging and less severe bingeing were linked to greater weight gain, while more frequent bingeing combined with infrequent purging reduced this effect.

    Major strengths

    • Open access data and code- Transparency was improved by the publication of code and data on the OSF, supporting reproducibility and future research.

    • Easy to follow- This paper was well-structured and clearly presented, making it an easy read. 

    • Novelty- Inclusion of bingeing and purging as a predictor of weight change adds a unique perspective, going beyond traditional factors like weight suppression and BMI.

    Major issue

    • Limited Practical Impact- Overall weight gain during treatment for bulimia nervosa is typically minimal, raising concerns about the study's practical significance. The authors should clarify how predicting small weight changes contributes to treatment planning- Is there evidence that predicting weight gain could enhance adherence? A stronger discussion of how weight gain may impact treatment adherence and how clinicians could use these predictors in therapy would improve the study's contribution.

    Minor issues

    • Stronger Literature Grounding- The introduction lacks citations of key relevant studies, including:

      • 'Impact of pre-treatment weight on weight trajectory in women treated for bulimia nervosa' (Carter et al., 2004)

      • 'Patterns of weight change after treatment for bulimia nervosa' (Carter et al., 2004)

      • 'The independent and interacting effects of weight suppression and admission body mass index on treatment weight change in patients with anorexia nervosa or bulimia nervosa' (Piers et al., 2019).

    • Duration of Treatment- The average length of inpatient stay is not reported, making it unclear how much of the typical treatment duration the study captures. Relatedly, consider removing claims that this study measures 'from admission to discharge'.

    • Placement of Linearity Testing Results – The results of testing the linearity of weight change should be moved from the Analysis section to the Results section, as they are discussed as a finding in the Discussion and Abstract.

    • Significance Threshold – The use of a stricter significance level (p < .005) to reduce false positives is commendable. However, confirmation that this decision was made a priori (e.g., through pre-registration) would have strengthened the study's methodological transparency. We note that this cannot be rectified now.

    • More Meaningful Interpretation of Results – The study could present findings in more clinically relevant terms, such as: "One extra weekly purge is associated with X increase in BMI over 10 weeks." This would enhance the practical understanding of the results.

    • Narrow Discussion- While the authors commendably avoid overextending clinical implications from limited data, the discussion could provide a deeper analysis of the study's relevance. Instead of primarily calling for further research, the authors could explore potential clinical applications based on their findings.

    Competing interests

    The authors declare that they have no competing interests.

  2. Version published to 10.31234/osf.io/7z4hq on OSF Preprints