PEER REVIEW HISTORY ARTICLE DETAILS VERSION 1 - REVIEW

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1 PEER REVIEW HISTORY BMJ Open publishes all reviews undertaken for accepted manuscripts. Reviewers are asked to complete a checklist review form ( and are provided with free text boxes to elaborate on their assessment. These free text comments are reproduced below. ARTICLE DETAILS TITLE (PROVISIONAL) AUTHORS Women s weight and disordered eating in a large Norwegian community sample: The Nord-Trøndelag Health Study (HUNT) Eik-Nes, Trine; Romild, Ulla; Guzey, Ismail; Holmen, Turid; micali, nadia; Bjørnelv, Sigrid VERSION 1 - REVIEW REVIEWER REVIEW RETURNED Deborah Mitchison Macquarie University, Australia University of Western Sydney, Australia 06-May-2015 GENERAL COMMENTS OVERVIEW This study assessed the prevalence and relationships between weight, eating disorder pathology, dieting, weight dissatisfaction, and demographic variables in a large cross-sectional sample of women from the general population. Overall, the study is promising and will provide much needed population-based information regarding the variables explored. The strengths of the study are obvious and include the very large sample size and the objective measurement of weight and height. The comparative weaknesses of the study include the use of less well-established measures of eating disorder symptoms, which was acknowledged by the authors, but also more notably the exclusion of male participants. I have listed a number of review points, however most of these are minor/discretionary. The main concern that I think necessary for the authors to address is to add methodological detail that will aid the readability and interpretability of the manuscript. These details include foremost the item content of the EDS-5, the reasons males were excluded, the reason that younger participants received the EAT-8, and participant selection and recruitment. ABSTRACT - Perhaps explain in the abstract briefly what disordered eating means. Some readers will identify dieting as a form of disordered eating, so the differentiation in your study needs to be made clearer. INTRODUCTION - Paragraph 1: Please include citations to population-based research to support the first sentence that eating disorders and eating disorder symptoms are increasing. - Paragraph 3: (last sentence) I am surprised/interested in the authors comment that research has revolved around overweight people perceiving themselves as normal weight - please cite

2 relevant research here. Also I suggest change research on weight and weight dissatisfaction to be more specific to what the authors are trying to claim, such as research on weight perception. METHODS - Under Study Population, please include information about the recruitment or random selection methods employed. For example, was this a household survey? How were potential participants identified and contacted? Also include details on how the clinical examinations were carried out. Were the questionnaires and examinations completed at the same time? - Figure 1: Please expand all acronyms, and provide the age ranges of the younger and older cohorts in the figure or in a footnote. This will ensure the figure can stand-alone. - The heading Measures is missing, and should appear before the heading disordered eating. - Why were the male data excluded? Given males were included in the HUNT Survey, it would be a shame not to compare men and women in the analyses employed in this study. Especially given that the prevalence gap between men and women in terms of DE appears to be closing, and the impairment associated with DE is roughly commensurate between men and women. - The EAT-26 was greatly modified in the present study, which precluded comparison to other studies that employed the EAT-26. The number of items on the subscales used were reduced, and the number of response options were also reduced from a 6-point scale to a 3-point scale. Were there 4 items included on each of the EAT- A and EAT-B? Given there is only 8 items, could the authors list the aspects of pathology that they each item assesses? - It is not clear why the EAT-8 was given to the younger cohort while the majority of participants received the EDS-5. This greatly reduces the ability to compare across age groups in this study, and thus needs to be explained. - Chronbach s alpha for the EAT-8 in this study? - Suggest rephrase In this study, we used a score in score in the 90th percentile, which corresponded to a sum-score of 23 as a cutoff to In this study, participants who scored above the 90th percentile (score > 23) were considered at-risk of having an ED or similar. - Please provide more details on what the 5 items of the EDS-5 measure. If the reader knows more about the exact nature of the short scales (the EAT-8 and EDS-5) they will be in a better positon to interpret the results. - Please briefly provide details or reference to the clinical sample used to compare scores on the EDS-5. - I wonder why the last 10 years was chosen when asking about participants dieting behaviour? This time frame seems too long for participants who are either very young (19 years-old) or old (80+ years-old) in terms of relevance and recall. On the other hand, you found large effect sizes with this variable and so this is a minor comment to consider. - Second sentence under Ethical Approval : should finish sentence with approved the study. Or similar. RESULTS - Paragraph 1: provide BMI parameters for extreme obesity - Table 1: provide BMI parameters in brackets for weight categories; expand the acronym BMI in a footnote; it is unclear what the

3 percentages next to the ED items are indicating? Although this is explained later in the text, tables should be readily interpretable without reference to the text please make this clearer by editing the row titles or adding information to a footnote to the table; the dieting data is missing from Table 1 - Paragraph 2: stick to the wording screened positively on the oral control scale and screened positively on the builimia and food preoccupation scale rather than using terms such as EAT-B cases. - The authors report that DE was modestly associated with lower age in the year-old age group. The relationship with age is likely to have been stronger with a wider age range as later acknowledged in the Discussion. - Table 2: The authors should consider adding a * next to significant ORs to allow readers to quickly identify significant relationships (underweight more likely to score high on oral control; obese more likely to score high on bulimia and food preoccupation). - Paragraph 3 and 4: No need to restate the ORs and CIs in text, as they are already in Table 2. - Paragraph 3: In the second last sentence, what is meant by smokers being occasionally less likely to have higher EAT-B scores? - Paragraph 4: Scores on the EDS-5 were higher among overweight and obese older participants. Given that bulimia and food preoccupation was also higher amongst obese participants in the younger group, is the EDS-5 also more of a measure of this type of DE (as compared to oral control)? It is essential that the authors provide a better overview of the nature of the questions in the EDS-5 to aid interpretation of the results and make some sort of comparison to those in the younger group. - The authors report proportions of participants in weight categories reporting weight satisfaction versus weight dissatisfaction. It was somewhat misleading to report these figures without the results of the analysis in the same paragraph. The results of the analysis are reported in the next paragraph and were not significant. I suggest that the authors either begin the first paragraph under Dieting and Weight Dissatisfaction with the sentence Weight dissatisfaction was unrelated to BMI and age in crude and adjusted models and then go on to report the proportions of satisfaction/dissatisfaction in each weight category, OR, finish the paragraph with the sentence However, weight dissatisfaction was unrelated to BMI and age in crude and adjusted models. - When the authors write More than half (54.1%) reported dieting, are they referring to the whole sample of year-olds or to just the proportion who reported weight dissatisfaction? DISCUSSION - Paragraph 1: given other rates are reported, please add the % of participants reporting weight dissatisfaction - Paragraph 1: A trivial point. I am wary that there is a substantive difference between dieting and intention to lose weight and the authors should be cautious of using the terms interchangeably. Certainly intention to lose weight could predict dieting, however it may also predict other weight loss behaviours, and may at times be associated with no weight loss activity at all. - Paragraph 2: again, sentence 1 should include reference to population-based studies of disordered eating, given that they do exist. - Paragraph 2: although interesting, the commentary on geographic location comes as a surprise to the reader. I recommend including

4 some context to this discussion in the Introduction. - Paragraph 5: the authors comment on a hypothesis that dietary restraint may lead to binge eating in obese individuals to explain their finding of higher DE in obese participants. It is difficult for the reader to consider this hypothesis without first knowing what types of behaviours were assessed in the EDS-5. - Paragraph 6: health behaviour, such as? Can all forms of dieting really be considered health behaviour (for instance including extreme caloric restriction)? - Paragraph 7: Change underweight women believed they were too heavy to many/most/nearly two-thirds of underweight women believed they were too heavy. - Paragraph 8: 60% of obese participants in the current study were dissatisfied with their weight the majority of participants. They were not more likely to be dissatisfied with their weight than people at a lower weight, which is interesting. However they were still on the whole dissatisfied with their weight, which is in line with other research. The large minority of obese pts who were satisfied with their weight are indeed of interest and it would be beneficial to explore whether this has been adaptive in preserving emotional health at a higher weight (even if it is at the cost of physical health). - Paragraph 8: why do the authors assume that weight satisfaction equals inaccurate weight perception? This would be an interesting line of inquiry, however not one tested here. - Paragraph 9: the authors discuss the lack of an association between weight dissatisfaction and age and hypothesise that the thin ideal is now affecting all age groups. Have the authors also considered the possibility that while weight dissatisfaction may be prevalent across ages, more pathological indicators of body image disturbance such as overvaluation of weight/shape or preoccupation of weight/shape may vary across age groups? - Paragraph 10: do the authors mean that women with a higher education were more likely to report weight dissatisfaction? - Paragraph 11: The authors comment on ethnicity however have not reported this in Table 1 alongside other demographic variables. - The ORs for DE were increasingly higher for higher weight categories. This point is interesting and was not emphasised in the Discussion. What does it possibly mean? Is it reflective of more frequent binge eating in the larger weight categories, or as BMI increases is it the case that women more frantically engage in restrictive weight loss behaviours? Or is the increased levels of DE in higher weight groups less indicative of behavioural disturbance and more indicative of body image disturbance? These questions will be somewhat addressed by providing more detail on the nature of items in the EDS-5. The reviewer also provided a marked copy with detailed comments. Please contact the publisher for full information about it. REVIEWER REVIEW RETURNED Manuela Ferrari School of Health Policy and Management, York University, Toronto, Canada 11-May-2015 GENERAL COMMENTS Please see attached PDF. Many thanks. The reviewer also provided a marked copy with detailed comments.

5 Please contact the publisher for full information about it. REVIEWER REVIEW RETURNED Anna Keski-Rahkonen Department of Public Health, University of Helsinki, Finland 15-May-2015 GENERAL COMMENTS This very interesting study looks into the population prevalence of disordered eating, dieting and weight problems in Norwegian women. The study has several strengths, it is population-based and comprises different age groups. Overall, the study is well-written and clearly analyzed. Just a few comments 1. 'weight problems' is a difficult construct. In the abstract, the authors do not define the construct. If it refers to overweight and underweight, this may be misleading, as not everyone underweight or overweight sees her weight as a problem. 2. the verb 'instigate' in the abstract and strength/limitations is problematic; if the studies were cross-sectional, therefore not informative on temporal or causal relationships 3. the methods section needs a clarification - I assume that the study was not longitudinal (three waves tracking the same participants) but that three separate surveys with different participants were conducted. It is difficult to link the verbal description and the flowchart, 4. the prevalence of disordered eating calculated in this paper depends on the cut-off point defined by Bjomelv, Mykletun & Dahl who stated: "The prevalence of eating problems ranged from 0.3 to 47.0% depending on the definitions used." I was unable to access the full text version of the paper. More details justifying the cut-off and perhaps some sensitivity analyses using different cut-off point should be given. Were these cut-offs defined in the context of the present HUNT study or in a separate, independent sample? 5. p 7 row 44/45 conflating ethnicity and education in the beginning of Results is makes it difficult to understand the basic sociodemographics of the study sample 6. in Results, the given prevalences would be easier to put into context were their confidence intervals given. It would also be interesting to see the distribution of the raw EAT scores. Because various age groups were participating, wouldn't it make sense to calculate age-adjusted prevalences? 7. the discussion was in parts a bit rambling, and also felt somewhat superficial; the present study results (particularly disordered eating) were compared to few other studies. Surely there are a few more? A rewrite would improve the paper. 8. the last sentence of discussion before conclusions is difficult to interpret 9. if the study includes measurements conducted at different time points, a few words about how the authors dealt with age/period/cohort effects would help 10. the conclusions section sounds tentative and could be improved - please also harmonize it with the conclusions in the abstract, avoiding overinterpretation of the results

6 VERSION 1 AUTHOR RESPONSE Your comments and those of the reviewers were highly insightful and enabled us to greatly improve the quality of our manuscript. We hope that the revisions in the manuscript and our accompanying responses will be sufficient to make our manuscript suitable for publication in BMJ Open. The limitations and the weaknesses of the study are agreed upon, largely due to our use of less wellestablished measures of eating disorder symptoms. In the following pages are our point-by-point responses to the main comments of the reviewers. The exclusion of male participants The exclusion of male participants is for many reasons unfortunate, as the gap between men and women in terms of DE appears to be closing, as stated by one of the reviewers. However, DE is still more common in women and we sought to investigate specific associations in women. Nevertheless, it would have been very interesting to also study males and it is not unlikely that the authors will include men in future studies of DE as male participants are included in the HUNT study. We have added this to the paper Item content of the EDS-5 The item content of the EDS-5 and a more detailed description of the clinical sample assessed with the EDS-5 has been added to aid the readability and interpretability of the manuscript. The item description will help the readers understand the nature of the questions in the EDS-5 and enable readers to do some comparison to those in the younger group. We believe, as commented by the reviewers, that this addition will give the readers a better position to interpret the results and compare the aspects of DE pathology in the two different measures. Why was the EAT-8 given to the younger cohort while the majority of participants received the EDS- 5? A shortened version of the EAT, was given to the young adults in HUNT3 as they were follow-up participants from the adolescent part of the HUNT studies (Young-HUNT), however the psychiatric advisory group of HUNT3 decided to use EDS-5 in the older age group. Thus, for the majority of women (>30 yrs. old), the EDS-5 was used as an assessment of DE. The use of two measures is as pointed out by the reviewers, unfortunate, as it greatly reduces the ability to compare across age groups in this study. This is added to the discussion, and the description of the items of the two measures is added to ease comparisons between age groups. Tables As response to the reviews we have calculate age-adjusted prevalence rates and added a new table with age adjusted prevalence as various age groups were participating. Lack of confidence intervals Confidence intervals for the prevalence of DE are given as pointed out by one of the reviewers. The given prevalence rates will be easier to put into context when their confidence intervals are given. Also, confidence intervals are calculated and added to the age adjusted prevalence table. The distribution of the raw EAT scores The raw mean sum scores, SD and Mdn is added to the text. We did not add a table with a histogram of this distribution in the text due to the limit of five tables and figures. (A histogram is added in the attached copy of the decision letter for the editor and reviewers, as we were unable to add this histogram in this scholar one text box). An appendix of additional methodological details of the EAT-8 such as a Principal Component Analysis, and raw sum-scores of each item of EAT-8 can be added at the reviewers request.

7 Recruitment and selection methods The HUNT Study invites the total population of Nord-Trøndelag County, Norway, inviting inhabitants 13 years and older. Inhabitants yrs. participated in Young-HUNT. Three surveys have been conducted, (HUNT , HUNT and HUNT ). Each survey is crosssectional, but as HUNT is population based, many of the participants have participated in more than one survey and thus HUNT also represent longitudinal data. The study included measurements conducted at the same time points. However, as mentioned, the study population was given two different measures of DE due to disagreement in the planning period of HUNT3. The Methods section has been altered according to the reviewers comments for clarification. A more thorough and detailed description of the HUNT studies and the Young HUNT study are given in two separate articles: Krokstad, S., et al. (2013). "Cohort Profile: The HUNT Study, Norway." International Journal of Epidemiology 42(4): Holmen, T. L., et al. (2014). "Cohort profile of the Young-HUNT Study, Norway: a population-based study of adolescents." International Journal of Epidemiology 43(2): Modification of the Eating Attitude Test, sensitivity and specificity. The original version of the EAT with 40 items was considered too lengthy for the HUNT studies, including the shortened versions of the instrument; the EAT-26, EAT-12. Hence, the EAT-8 was greatly modified in the present study. As commented by the reviewers, this precludes comparison to other studies that employed the EAT-26. However, these two revised and short versions of the EAT have shown to be highly correlated (r =.98) (Scheinberg Z, Koslowsky M, Bleich A, Mark M, Apter A, Danon Y, Solomon Z, Babur I. Sensitivity, specificity, and positive predictive value as measures of prediction accuracy: the case of the EAT-26. Educ Psychol Meas. 1993;2(53): ). A large study in Norway ( Young in Norway ) validated the 12-item structure of the EAT-12. Four items from each of the three factors in the revised EAT-26 were chosen to assess DE in "Young in Norway". The 12 selected items had high factor loadings on the three factors independently and appeared clinically meaningful for the researchers at the time. EAT-26 applies a 6-point scale, while a 4-point scale was used in the "Young in Norway" study using 12 items from the EAT. In the Young-HUNT-1, only seven of the items from EAT were used to assess DE. The dieting factor was removed, and the remaining items used in the Young-HUNT study consisted only of the two factors, oral control (EAT-A) and bulimia and food preoccupation (EAT-B). Vomiting seemed to be a very infrequent behavior in Norwegian adolescents and the item had low loadings on the factor bulimia in the Young in Norway study. The vomiting item from the factor bulimia and food preoccupation was subsequently omitted in the Young-HUNT study, resulting in the use of seven items from the EAT (EAT-7). In this present study using data from the HUNT 3 study, the vomiting item was included in the assessment of DE, using eight items from the EAT (EAT-8). The original factor of dieting was neither in Young in Norway-study or any of the HUNT studies included. Dieting is often used as an indicator of DE and frequent in the Western world among adults, however in epidemiological studies such as this study, dieting was assessed using other questions. Reduction of number of response options in the EAT-8 and internal consistency As pointed out by the reviewers, the number of response options was reduced from the original versions and the following text has been added to clarify this: The original EAT applied a 6-point scale, while a 4-point scale was used in this present study. The items had 4 alternative answers: never, seldom, often, and always. In this present study never and seldom were recoded to zero (0), often as one (1) and always as two, which gave a maximum score of 8 for EAT-A and 8 for EAT-B in EAT-8. Cronbach alphas of the measures are also added to the text.

8 Cut off points/sensitivity analysis of EAT-8 The authors used the cut-off points defined by Bjørnelv et al. from the Young HUNT study. A twelveitem version of the EAT was as mentioned validated in a former Norwegian study (Young in Norway) and Bjørnelv et al later evaluated the consistency in terms of sensitivity and specificity between EAT-7 and EAT- 12 in an adolescent population (the Young HUNT). Hence, the cut-offs used in this present study were not defined in the context of the present study, but in the sample using the Young HUNT data. Details justifying these cut-offs can be found in Bjömelv, S., et al. (2002). "The influence of definitions on the prevalence of eating problems in an adolescent population." Eating and weight disorders : EWD 7(4): Unfortunately, we were not able to do sensitivity analyses using different cut-off point as as we did not have the opportunity to compare the EAT-8 and the EDS-5 with another test, using a gold standard technique with one group being normal (negative). Hence, comparisons of prevalence rates with other populations must be tentative. Why was the last 10 years was chosen when asking about participants dieting behaviour? As noted by the reviewers, a 10 year time frame is long for participants who were either very young (19 years-old) or old (80+ years-old) in terms of relevance and recall. This time frame was probably chosen as the HUNT surveys have been completed at 11-year intervals. Alterations of the background, discussion and conclusion due to recommended literature A rewrite of the background and the discussion has been made, largely due to the many articles recommended by one of the reviewers. Specifically, the authors are thankful for the contributions of recommendations on the current state of knowledge on the relationship of ED and weight related problems. The authors are grateful for the valuable articles added to capture this relationship We feel that the valued addition of the recommended literature largely enhanced the manuscript.