General population normative scores for interpreting the BODY‐Q (2025)

1 INTRODUCTION

Since 1975, obesity has tripled with over 650 million people worldwide living with obesity.¹ Weight loss interventions, including lifestyle, medical, and surgical treatments, all aim to achieve long-term weight loss and remission of obesity-related co-morbidities.^{2, 3} However, massive weight loss often leads to people having varying amounts of excess skin, where subsequent body contouring surgery (BC) is needed.^4-6 To facilitate evidence-based and patient-centred care, understanding the impact of different weight loss treatments and subsequent BC on patients' lives is pivotal to optimising outcomes.⁷

Patient-reported outcome measures (PROM) are questionnaires used to measure health outcomes from the patient's perspective. To accurately measure patient-reported outcomes (PRO) validated, reliable and responsive condition-specific PROMs are needed.⁸ Over the past decade, a vast array of PROMs have been used in weight loss and BC, many of which do not possess strong evidence of reliability and validity for the patient population.^9-12 The BODY-Q, introduced in 2016 is a rigorously developed and psychometrically validated PROM that measures outcomes of patients who undergo weight loss and/or BC.^{4, 13-15} The BODY-Q was developed following internationally recommended guidelines for PROM development and used a modern psychometric approach to measure concepts that matter most to patients. The conceptual framework covers four domains: appearance, health-related quality of life (HRQL), experience of health care, and eating-related concerns.^{12, 14, 16} The four domains are organised into independently functioning scales (Figure1), allowing the researchers and clinicians to administer the scale(s) that is most relevant to their practise or research question and reducing overall burden on patients.¹⁷ The BODY-Q has been shown to be responsive to change and subsequently, can be used to measure change over the entire weight loss trajectory, i.e., from obesity to weight loss with or without BC.^{14, 18, 19}

Since its development, the BODY-Q has been increasingly used worldwide.^{4-6, 20-24} Recent systematic reviews based on the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) methodology recommended the BODY-Q as the psychometrically strongest PROM for use in weight loss, particularly in bariatric surgery (BaS) and BC.^{12, 13} However, a current limitation of the BODY-Q is the lack of available general population norms as a reference point of the levels of satisfaction with appearance, eating-related concerns, and HRQL. Although the BODY-Q has been used to demonstrate the efficacy of weight loss therapy and BC,^{4, 22} it is not yet known how published preoperative and postoperative scores compare to population norms. Scores from the general population would enable a better understanding of HRQL of obesity and change through the weight loss trajectory.

The primary aim of this study was to determine BODY-Q scores for the general population as reference values for comparative purposes in research and clinical use. The secondary aim was to compare normative scores for North America and Europe, and to investigate associations between BODY-Q scores and age, gender, and body mass index (BMI).

2 MATERIALS AND METHODS

We conducted an international study to collect BODY-Q scores from the general population in a total of 12 countries in North America and Europe. The European sample was approved by the Danish data protection agency. In Denmark, ethical approval is not required for survey-based studies. The North American study sample was approved by the institutional review board (Mass General Brigham [MGB] Institutional Review Board [IRB], United States [US]). All data and informed consent were obtained electronically in accordance with the Danish data protection agency and the MGB IRB.

3 RESULTS

4 DISCUSSION

In this study, we presented BODY-Q normative scores generated from an international sample of 4051 participants from a total of 12 North American and European countries. The overall and continent-specific normative scores were provided for 22 BODY-Q scales from three domains – appearance (12 scales), HRQL (7 scales), and eating-related concerns (3 scales). The normative scores for all scales are presented stratified by age, BMI, and gender (male and female). These normative values provide means to interpret the BODY-Q scores for use in research and clinical practise.

The development of PROMs that evidence validity, responsiveness and reliability, the BODY-Q, have facilitated investigation of the unique outcomes of weight loss and/or BC from the patient perspective.^{4, 14, 22} The BODY-Q can be used clinically and as a research tool to shed light on our understanding of the effects of losing weight and following BC procedures on perceptions of appearance, HRQL and eating behaviour.^{12, 16} This is the first study to date to generate normative values for interpreting the BODY-Q. Previous outcome studies using the BODY-Q to measure change of satisfaction with appearance and HRQL in BaS and BC patients revealed significantly higher mean BODY-Q scores after BaS. In addition, the studies showed significantly higher scores for patients who received BC following BaS compared to patients who did not.^{4, 6, 23, 24} However, these scores were limited by not being able to compare their findings to reference values from the general population. Measuring a return to normality is important; thus, there is a need for an appropriate reference point for weight loss- and BC patients. The values provided in this study enables accurate comparison with the general population enhancing the interpretation of BODY-Q data to understand the actual impact of weight loss and BC on different aspects of patient's lives. The findings of this study have important implications for research, future clinical care, and healthcare policy.

Normative scores have been generated for the generic 36-Item Short-Form Health Survey (SF-36), and European-Quality of life-5 Dimensions (EQ-5D) which is the most widely used generic PROMs in obesity and weight loss treatment.^36-38 However, generic PROMs lack content validity and may not capture specific concepts of matter for weight loss and BC patients.³⁵ The lack of sensitivity or responsiveness for weight loss and BC specific outcomes, may minimise or not detect changes as a result of weight loss or BC.^{19, 39} Nonetheless, our findings were in line with the normative SF-36 scores with females having lower scores than males in regards of satisfaction with appearance and body image.^{36, 37} In contrast to other studies investigating population norms, there are no differences in the scores of females and males in HRQL and eating-related concerns scales.^{36, 40} Younger age was negatively associated with BODY-Q scores contradictory to normative EQ-5D scores, where younger age was associated with higher scores.^{38, 41}

Opposing to our hypothesis of minimal differences between scores across the 12 countries, we detected significant differences between North America and Europe, and between some European countries in all appearance scales and social function, sexual function, body image, and work life within the HRQL scales. Differential item functioning (DIF), which describes the stability of the BODY-Q instrument to determine whether items are responded differently by subgroups within a population, has been examined elsewhere in the original BODY-Q population, and found to have a negligible impact.^{14, 18} The differences detected in this study are therefore most likely not due to DIF, but rather due to cross-cultural differences between countries. There might be differences in the experience and conceptualization of HRQL across different socio-cultural groups, which further emphasized the need of general norms to understand the clinical significance and magnitude of the change weight loss and/or BC have on patient's lives.^{42, 43} Interestingly, there were no differences between North America and Europe in eating-related symptoms- and eating behaviour scales, while European participants scores significantly higher scores in eating-related distress. Cross-cultural factors such as cultural beliefs regarding food preferences and culinary habits have shown to influence individual's eating behaviour and relationship with food.^{44, 45} Due to differences in eating cultures, we expected differences between countries, especially between the two continents. The eating-related concerns domain is however a newly developed scale, and only available in few languages (English, Danish, and Dutch). Therefore, data is solely based on North America, the Netherlands, and Denmark. More cross-cultural research is needed to identify causes of differences and similarities between countries. However, all data were adjusted for country as a covariate when the total normative value was determined, due to these differences between the distribution of BODY-Q scores from different countries and continents. The sample was more representative when both continents were combined, with a mean age of 36 (±14.7 SD) years, 11 996 (49.3%) female, 2023 (49.9%) male, and 32 (0.8%) other gender identifications. Therefore, we recommend the use of the combined normative values for comparative purposes.

The secondary aim of this project was to investigate factors associated with BODY-Q scores. BMI and age were inversely associated with BODY-Q scores in all satisfaction with appearance and HRQL scales. Our results points to the fact that living with obesity represents a significant health impairment.⁴⁶ In the normative data split by gender for the different age and BMI groups, females had lower satisfaction with appearance corresponding with the normative SF-36 scores.^{36, 37} Female participants with a BMI 25.5–30.0kg/m² scored below 25, while male participants scored below 25 from BMI 35–40 kg/m². The same pattern was seen in body image, where female participant scored below 25 from BMI 30–35 kg/m², whilst male participants scored below 25 from BMI >40. The only exception was for male participants in the age group 17–29 years, who scored below 25 from BMI 35–40 kg/m². In the remaining HRQL and eating-related concerns scales, male and female participants scored similarly.

Strengths of our study is the large international sample of 4051 participants to match the diverse population of weight loss and BC patients. Online crowdsourcing databases such as Prolific and MTurk has shown to be a valid and reliable method for recruitment of research participants, facilitating cross-cultural and international research with low costs and high validity.^47-50 However, a potential limitation of this study is whether the recruitment of participants via the crowdsourcing platforms is representative of the general population of the included countries or not. An important limitation of this study is the ethnical diversity. In total, the population consisted of 87.9% participants who identified themselves as white, while only 12.1% identified themselves as another ethnicity. Therefore, the ethnical homogeneity should be considered with caution when interpreting these normative results. In addition, participants were paid to participate, which may have impacted incentives of participation in this study and their responses to the questions. In the European sample, the participants were younger. This is in line with other studies using crowdsourcing databases, with participants being younger, more educated, reporting lower rates of unemployment and marriage.⁴⁷ However, all mean scores were adjusted for age, employment, and marital status. The skin, stretch marks and cellulite scales consisted of a small number of participants, which should be considered when interpreting these results. Future research is needed to compare longitudinal BODY-Q patient results to these normative data.

5 CONCLUSION

The normative values generated in this study provide clinically relevant reference points for the interpretation of the BODY-Q with appearance, HRQL, and eating-related concerns scales. The normative BODY-Q scores were inversely associated with age and BMI for all appearance, HRQL, and eating-related concerns scales. These normative data enable us to understand the impact of weight loss and BC on patient's lives for research, future clinical care, and health care policy.

CONFLICT OF INTEREST

Anne F. Klassen and Andrea L. Pusic are co-developers of the BODY-Q and receive a share of any licence revenues based on their institutions inventor sharing policy. Anne F. Klassen is an owner of EVENTUM Research which provides consulting services to the pharmaceutical industry. The remaining authors declare no conflicts of interest.