Date of Award


Degree Type

Restricted to Claremont Colleges Dissertation

Degree Name

Health Promotion Sciences, PhD


School of Community and Global Health

Dissertation or Thesis Committee Member

Kim Reynolds

Dissertation or Thesis Committee Member

Alan Stacy

Dissertation or Thesis Committee Member

Bin Xie

Terms of Use & License Information

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

Rights Information

© 2023 Jennifer Thayer


Clinical Practice Outcomes, Implicit Bias, Registered Dietitian Nutritionist, Weight-Related Bias

Subject Categories

Medicine and Health Sciences | Nutrition


Prior research has examined the effect of body weight on the development and successful treatment of multiple health conditions, including chronic diseases such as heart disease and diabetes. While a person’s weight is increasingly recognized as being due to many factors, diet and other lifestyle behaviors are currently at the forefront of addressing overweight and obesity in the United States. Registered dietitian nutritionists are trained both in educating patients about how diet and lifestyle behavior choices can affect health and assessing a particular patient’s diet and lifestyle to evaluate which dietary recommendations could best address a particular food-related medical or behavioral diagnosis. Weight-related implicit bias has been reported in multiple healthcare professions and has been considered as a factor in affecting treatment decisions made by practitioners. A limited amount of research on weight-related bias has been conducted among registered dietitian nutritionist practitioners, especially regarding patient assessments and intervention recommendations. Weight-related implicit bias is a growing area of research in this community. Several studies have examined the correlation between weight-related bias among nutrition practitioners and weight-related explicit bias or practice outcomes, finding significant differences in practice outcomes relative to levels of bias. There have also been interventional studies in this community which attempted to produce changes in weight-related implicit or explicit biases, although no significant differences were seen between pretest and posttest scores. The first aim of this study was to examine the effect of exposure to a potentially implicit bias triggering event on weight-related implicit bias in the registered dietitian nutritionist community. Using an online survey, we measured weight-related implicit bias among registered dietitian nutritionists (RD/RDNs) and nutrition and dietetics technicians, registered (DTR/NDTRs) using the Weight Implicit Association Test (Weight IAT) before and after exposure to a randomized case study experiment describing a client reporting for nutrition counseling due to a caffeine intolerance who was described as having a BMI either in the normal or obese range. Analyses were then conducted to examine pre-post changes in weight-related implicit bias across experimental conditions (High BMI case study vs Low BMI case study). Analyses indicated no significant effect of case study exposure (High BMI versus Low BMI) on levels of weight-related implicit bias. The second aim was to test the effect of the experimental manipulation (High BMI vs Low BMI) on assessment and intervention recommendations provided by the participant. After exposing the study participants to the case study, they were asked to assess the client’s caloric intake, diet quality, physical activity level, and overall health and whether they would make weight-related intervention recommendations for a client. They were also asked if they would have liked any additional information about the client and, if so, what specific information they would have liked. ANCOVA analyses revealed that the group exposed to the high BMI case study was significantly more likely to report weight-related intervention recommendations for the client described in the case study both in the entire Intent to Treat group (Experimental condition n = 34, adj. mean (SE) = 2.316 (0.171), Control condition n = 32, adj. mean (SE) = 1.543 (0.176), p < 0.019) and the Intent to Treat group that had completed both the pretest and posttest IATs (Experimental condition n = 25, adjusted mean (SE) = 2.127 (0.185), Control condition n = 25, adjusted mean (SE) = 1.433 (0.185), p = 0.011). No significant effects were found for the summed assessment outcome variable (comprised of the sum of the assessment scores for caloric intake, diet quality, physical activity level, and overall health) or the variable assessing desire to have additional information about the client. The present study found that exposure to a High BMI client, as described in a case study, did not affect or further activate weight-related implicit bias relative to a Low BMI client. This could have been due to the relatively immutable nature of implicit biases, saturation exposure to multiple measures of weight-related explicit bias, or something specific about the case study itself. It also could have been due to those who chose to remain in the study and complete both IATs along with the practice outcome questions creating a selection bias which affected external validity. A significant effect of the treatment condition was found indicating an increased likelihood of making weight-related intervention recommendations to the client. As many practitioners have been trained to consider weight in all evaluations, this was the predicted result for this practice outcome, and could have been due to multiple factors, including bias or the specific focus of the RD/RDN training received. There were no significant effects of treatment condition on either assessment or desire for additional information about the client.



Available for download on Thursday, March 05, 2026