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Obesity bias has been shown to undermine the patient-doctor relationship and lead to substandard care. A valid and reliable instrument was developed to measure medical students’ attitudes and beliefs about obese patients.
The authors conducted a literature search to identify validated measures of obesity bias. Since no appropriate scale was located, the decision to design a novel survey instrument, titled the NEW (Nutrition, Exercise and Weight Management) Attitudes Scale, was made. An expert panel generated items which were then discussed in focus groups of third year medical students. Experienced medical educators served as judges, weighting the items using a Thurstone scale. Second and fourth year medical students completed these items alongside two previously validated measures of obesity bias, the Anti-Fat Attitudes Questionnaire (AFA) and Beliefs About Obese Persons Scale (BAOP). Third year students completed the NEW scales before and after a simulated encounter with an obese standardized patient instructor.
Thirty one items comprised the final instrument. A sample of 201 judges rated the positivity of items. A sample of 111 second and fourth year medical students completed the survey (mean score 24.4, range −37 to 76 out of a possible −118 to 118); Pearson correlations between AFA and BAOP were −0.47 and 0.23, respectively. Test-retest reliability was 0.89. Students scored 27% higher after completing the standardized patient-instructor encounter (P<.001).
The NEW Attitudes Scale had good validity and reliability and may be used in future studies to measure medical students’ attitudes towards obese patients.
Prevalence of obesity in the United States has increased dramatically over the past few decades. Since 2010, prevalence of obesity has exceeded 20% of the population in all states with 12 states, concentrated in the South, having obesity rates in excess of 30%.1 Given the negative implications of obesity for an individual’s health, including predisposition to heart disease, diabetes, some cancers, and many other conditions,2 physicians must continue to work collaboratively with patients towards the goal of healthy weight loss.
Unfortunately, researchers have shown that physicians are not exempt from the biased views of obese persons that are so prevalent in the United States.3-5 Such views undermine the patient-doctor relationship and contribute to obesity stigma, which, rather than motivate patients to lose weight, contributes to a variety of physical and psychological problems.6,7 Even those doctors who specialize in treatment of obesity demonstrated negative attitudes and stereotypical perception of obese persons as lazy on an implicit association test.8 Hebl and Xu9 found that physicians held more negative views of obese persons compared to normal weight persons on 12 of 13 indices, including desire to help the patient and estimated duration of an appointment. Huizinga et al10 found that increasing BMI was significantly associated with a lack of respect for overweight patients.
Such negative inclinations also exist among medical students. Although Persky and Eccleston11 and Wigton and McGaghie12 did not find differences in students’ clinical decision-making, they did note bias in belief, attitudes and interactions on the basis of patient size alone. They noted that such biases could cause such patients to delay follow-up and preventive services. In turn, many obese persons report difficulty in pursuing medical care for a variety of reasons, such as lack of appropriate sized equipment and embarrassment about weight.13-15
Medical students comprise an enticing target for efforts to reduce obesity bias and obesity stigma in health care. Unfortunately, even though such bias is well-established and has been shown to affect patient care, many medical schools have not addressed the problem directly.16,17 In response to this need, our research team has recently developed and implemented a series of educational modules and an obese standardized patient program intended to challenge students’ attitudes and beliefs about obesity. We hypothesize that a more favorable disposition towards obese patients could undergird improved counseling and rapport building skills, perhaps leading to improved clinical outcomes.
In order to determine the efficacy of these and similar interventions17-19, a valid and reliable means of assessing medical students’ beliefs and attitudes towards obese patients is needed. In this article, we report the development of such an instrument, the Nutrition, Exercise, and Weight management (NEW) Attitudes Scale, and provide evidence of its validity and reliability.
The Wake Forest School of Medicine Institutional Review Board approved this protocol after expedited review.
The authors conducted a literature search to identify validated measures of obesity bias. Our PubMed/Medline literature search in August of 2008 resulted in 75 abstracts/articles on attitudes/measures regarding obesity. Out of the identified abstracts/ articles, we found several scales that assess beliefs and attitudes about obese persons, including the Anti-fat Attitudes Questionnaire (AFA), Anti-fat Attitudes Scale (AFAS), Anti-fat Attitudes Test (AFAT), Attitudes toward Obese Persons scale (ATOP), Beliefs about Obese Persons Scale (BAOP), and Fat Phobia Scale.20-24 None of these instruments was designed for medical students or emphasized patient care. The most relevant instruments are perhaps the AFA, BAOP, and the AFAS. However, for the purpose of the current study, these instruments have limitations. As Morrison and O’Connor observed,22 the AFA contains some ambiguous items, such as “I worry about becoming fat”, which carry the risk of conflating prejudice with concern for one’s own health. The 8-item BAOP focuses on beliefs about what causes obesity and lacks the breath of covering attitudes such as about weight management and counseling, which are important to this study. The 5-item Anti-fat Attitudes Scale (AFAS) focuses strictly on personal dislike of fat persons and lacks a specific target population. All of these scales also do not contain questions about attitudes within the context of a physician interacting with patients, rendering them unsuitable for our purposes.
After carefully reviewing known instruments, the investigative team made the decision to begin designing a novel tool, the NEW Attitudes Scale. The team generated new items and modified existing ones to form an initial item pool. The team divided the items into the domains of nutrition, exercise and weight management for further discussion and refinement. We combined revised items from each domain for use in focus groups.
Team members conducted 6 focus groups each of 6-9 third year medical students on their family medicine clerkship at Wake Forest School of Medicine (WFSM), site of the study. Students provided feedback and considered items for inclusion in the NEW Attitudes Scale. Students received small monetary compensation and lunch in exchange for their participation. The facilitator recorded each focus group; team members analyzed the notes to identify salient themes. Based on the results of the focus group discussion and the team review, we created a final list of 31 items.
In order to increase the accuracy of the NEW Attitudes Scale, the team assessed the final list of items using a Thurstone scale. Originally developed for achieving smaller bias and lower error variance in measuring attitudes about religion, the Thurstone scale has since been applied to a variety of subjects.25-27 For example, a Thurstone scale was recently used to identify desirable characteristics for police officers.28 Unlike the Likert scale, which gives equal weight to each item (typically in the form of a statement), the Thurstone scale uses differential weights for individual items/statements. Briefly, the Thurstone scaling approach solicits ratings on individual items from a panel of “experts” about the magnitude and direction of an attitudinal item. In this case, we requested experts in the field of medical education to serve as judges. They were asked to determine the positivity or negativity of each item, using a scale from 1 (unfavorable) to 11 (favorable). The judges did not directly respond to the items, but merely rated them for use by future survey respondents. The psychometric behavior of the NEW Attitudes Scale was improved by taking into account the differential discriminatory power of individual items. For example, a future survey respondent who endorses a very negative statement about obese patients would be viewed as more biased than one who endorses a mildly negative statement, rather than treating them as equally biased.
We determined the weight for each NEW Attitudes Scale item from the statistic of the distributions of ratings. We selected a robust statistic - the median of the distribution - to form the raw weight. To get the actual question weightings, six, the midpoint of the scale, was subtracted from the median ratings. For example, a question that received a median rating of “1” on the Thurstone scale was given an actual weight of −5 on the survey instrument, and a question rated as an “8” would get a weight of 2. We used the weights in the final instrument as multipliers and a 5-point scale to capture students’ response to each item: −2 (strongly disagree), −1, 0, 1 or 2 (strongly agree) points. By centering the scale at 0, positive scores would suggest positive attitudes, and vice versa. Thus, if an item had a weight of −5, and a student strongly disagreed (score of −2), the item would be scored as −5 × −2 = 10 points; if a student strongly agreed with that negative item, it would be scored −5 × 2 = −10 points.
We recruited judges (predominately faculty at medical schools) from both clinical and research backgrounds using the listservs of the Groups on Educational Affairs (GEAs) of the Association of American Medical Colleges (AAMC), which are divided into four regions: Central, Northeastern, Southern and Western USA. We also identified internal judges within WFSM and invited them to participate. All judges held an advanced degree.
We carefully built content validity into the NEW Attitudes Scale through a team development approach during the item generation process. Content experts that participated in the process included medical educators, nutritionists, physicians, and psychometricians. The team extensively reviewed the items to ensure that the items adequately covered the desired domains of the targeted construct.
We administered the finalized NEW Attitudes Scale to a convenience sample of second and fourth year medical students at WFSM who were recruited to take the survey by the program manager of the investigative team. Participation was voluntary, confidential, and independent of assessment or promotion. The study did not provide incentive to participants. Students not only completed the NEW Attitudes survey, but also completed two previously validated measures of obesity bias: the Anti-Fat Attitudes Questionnaire (AFA) and Beliefs About Obese Persons Scale (BAOP).20,23 To assess construct validity, we correlated the NEW Attitudes Scale with the other two scales. We expected the correlations to be moderate, demonstrating concurrent validity.
We further assessed construct validity by measuring medical students’ attitudes towards obese patients before and after an intervention intended to reduce stigma and bias. Specifically, third year medical students during their Family and Community Medicine clerkship at WFSM participated in a simulated outpatient visit with an obese standardized patient instructor (SPI). The patient presented to clinic with complaint of 5 pound weight gain and concern regarding her risk of cancer. After the encounter, the SPI then provided feedback meant to increase student confidence caring for this population and highlight the challenges of weight loss. If the NEW Attitudes Scale is appropriate and accurate, and the intervention works, the scale should detect a positive change in attitudes after the intervention.
We assessed reliability by testing a small volunteer group of third year medical students in a different class year and retesting them 2 weeks later to determine if scores changed. The team chose a two-week retesting to avoid the possibility of students’ attitudes actually changing. We assessed internal consistency using Cronbach’s alpha.
We used a factor analysis of the responses to test dimensionality of the scale. We first categorized the item into positive (Thurstone weight >0) and negative (weight ≤ 0) items and reverse-coded the negative item responses. We used a scree-plot to determine the number of factors and then applied factor analysis, based on varimax rotation, to delineate orthogonal factors.
We accounted for missing values by one of two ways: discarding surveys in which an excessive amount of information was missing or, if only a few answers were omitted, imputing missing data with a participant’s mean response to the other items. We discarded surveys if a subject did not answer at least 80% of the items.
The investigative team developed an initial item pool of 50 questions in the content domains of nutrition, exercise and weight management. The family medicine clerkship coordinator solicited volunteers from six clerkship rotations (10 students per rotation) to participate in focus groups; six to nine per rotation volunteered over the six month period. Students (n=42) completed the scale prior to the focus group and during the focus group they provided feedback on the item pool.
Focus group feedback led to refinement of the list and selection of 31 questions for inclusion in a revised instrument. Reasons that students suggested excluding questions included ambiguity and inability to discriminate well between respondents of different attitudes. For example, we excluded “I am likely to provide care for a significant number of overweight/obese patients in my practice” because students may have answered “yes” not because of any preference for such persons, but because they know that they make up a large portion of the US population. We updated some questions to reflect a level of training appropriate to medical students. Ultimately, 7 items pertained to nutrition, 6 to exercise, and 11 to weight management. Although another 7 questions did not fall into a specific domain we deemed these relevant to the scale.
A sample of 201 expert judges rated each of 31 questions using a Thurstone scale ranging from 1 (unfavorable) to 11 (favorable). Characteristics of the judges are provided in Table 1. Missing values were low, comprising 0.9% of responses.
Actual ratings ranged from 1 to 8. In Table 2, we report the actual items and weights of items (judges’ median score minus 6). Of note, several statements of attitude deemed to be neutral in nature, such as “Patients understand the connection between exercise and cancer,” received a raw median score of 6. Thus, neutral items received a weight of 0 and subsequently do not affect scoring on the NEW Attitudes Scale. Other items received decisively positive or negative ratings; for example, “I do feel a bit disgusted when treating a patient who is obese” received a median raw rating of 1 (weight of −5). Some variations were wide while others were narrow. The median, which is not as sensitive to outlying values as the mean, seemed a better choice for computing item weights.
A sample of 111 second year and fourth year medical students completed the NEW Attitudes Scale alongside the AFA and BAOP scales; 66 respondents were female, 55 were second year students. In Table 2 we report the percentages of respondents who agree (either 1 or 2 on the actual scale), feel neutral (0), or disagree (−1 or −2), as well as number missing for all items. The percentage of missing values was low. The mean imputation method for handling missing values, described in the Methods section, should be sufficient, and we do not expect results to differ with more advanced missing value methodology.
We identified three factors that respectively account for 15, 11, and 8 percent of variance. The factor analysis revealed the following dimensions: (1) anti-fat (e.g., item 23 “I do feel a bit disgusted when treating a patient who is obese”); (2) self efficacy and propensity to provide counseling to obese patients (e.g., item 12 “I have a personal desire to counsel patients about exercise”); and (3) belief about how others understand obesity (e.g., item 3 “patients understand the connection between nutrition and cancer”). Table 2 indicates the factor upon which each item is most loaded.
Table 3 shows the mean scores of students, stratified by gender and year, for all three obesity scales, including the NEW Attitudes Scale. The mean score on the NEW Attitudes Scale was 24.4. Out of a possible score of −118 to +118, the lowest score was −37 and the highest score was 78. Men and women respondents did not differ significantly. However, second year students were more positive than fourth year students (P=.01).
The Pearson correlations between the NEW Attitudes Scale and the AFA and BAOP were −.47 and .23, respectively. We expected a negative value for AFA, because a higher score on AFA indicates a more negative attitude towards obese persons (for both NEW Attitudes Scale and BAOP, higher scores indicate more positive attitudes towards obese persons). Thus, the NEW Attitudes Scale was moderately correlated with both AFA and BAOP. Figure 1 shows the distribution of scores on the NEW Attitudes Scale.
The test-retest reliability (correlation coefficient) of the 24 medical students tested at baseline and again 2 weeks later was .89. Cronbach’s alpha for the sample of 111 medical students was 0.63, suggesting moderate internal consistency.
A total of 103 third year medical students completed the NEW Attitudes Scale prior to a simulated encounter with an obese standardized patient instructor. As described in the methods section, students were retested after receiving feedback to determine if the scale could detect a change in attitudes. The mean score before the encounter was 25.5 and 32.2 upon retesting, a difference of 27% (P<.001, df=102).
Given the scale of the obesity epidemic, and the positive role physicians can play in healthy weight loss, the availability of an instrument with substantial evidence for reliability and validity that can assess medical students’ attitudes towards obese patients is both timely and significant. As efforts to change attitudes, such as curricula for obesity counseling, are employed, it is imperative to be able to accurately gauge the success of such interventions. The NEW Attitudes Scale represents a scientifically validated tool for capturing medical students’ attitudes towards obese patients and has the unique advantage of clinical focus.
Several strengths of the NEW Lifestyle Attitude Scale should be highlighted. First, the use of a Thurstone scale increases accuracy of the NEW Attitudes instrument by weighting individual questions. By giving individual questions a weight, a finer level of detail is revealed regarding subjects’ attitudes. Second, the scale shows strong evidence of face validity, content validity, concurrent validity, and criterion validity, as well as satisfactory internal structure. Third, the scale demonstrates a high level of reliability and its internal consistency is also satisfactory.
Given the average student score of 24.4 on the NEW Attitudes Scale, WFSM students appear to have a mildly positive attitudes regarding care of obese patients. We found this finding surprising given the previous studies that identified negative attitudes towards the obese in medical students.11,12 However, authors of those same studies did not report a difference in approach to management. Perhaps the more positive score can be accounted for by the clinical focus of the NEW Attitudes Scale. Students’ desire to provide excellent care may override personal bias. Also of interest is the finding that scores of the men did not differ significantly from those of the women across all three instruments, while fourth year students had more negative attitudes than second year students on both the NEW Attitudes Scale (0.48 SD difference) and AFA (0.63 SD difference). One might expect that attitudes would improve with increased experience caring for obese patients, but providers may become more skeptical of patients achieving weight loss over time.
The present article does have some limitations. Only third year medical students at WFSM were sampled in focus groups and only second and fourth year students participated in the survey, limiting generalizability. Also, although the instrument captured an expected improvement in scores after students completed the SPI encounter, efficacy of the intervention has not yet been determined. The detected effect may be short-term and not sustained. Finally, we have not been able to collect data for assessing longer term predictive validity. We expect attitudinal scores are likely to predict differences in approach to and/or management of obese patients in actual practice, but this needs to be investigated in future studies.
In conclusion, the NEW Attitudes Scale demonstrated good validity and reliability and may be used in future studies to measure medical students’ attitudes towards obese patients.
Funding/Support: NCI grant number R25CA117887-01A2
DISCLOSURES Other disclosures: None
Ethical approval: Expedited approval granted by the Wake Forest School of Medicine IRB.
Dr. Edward H. Ip, Department of Public Health Sciences at Wake Forest School of Medicine, Winston-Salem, North Carolina.
Ms. Sarah Marshall, University of California - San Francisco School of Medicine.
Dr. Mara Vitolins, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Dr. Sonia J. Crandall, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Mr. Stephen Davis, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Dr. David Miller, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Ms. Donna Kronner, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Ms. Karen Vaden, Wake Forest School of Medicine, Winston-Salem, North Carolina.
Dr. John Spangler, Wake Forest School of Medicine, Winston-Salem, North Carolina.