Daily Habits & Consumer Preferences Study

Obesity Stigma and Health Behavior: An Experimental Approach

The study will use a between-subjects design in a sample of individuals with BMI greater than or equal to 28 from the Los Angeles community (N=330). Participants will be randomly assigned to a weight stigma vs. control manipulation. Changes to the following health behaviors will be subsequently measured in their everyday lives: 3-day diet as captured by ecological momentary assessment (EMA) food diaries, objectively measured eating of obesogenic foods, objectively measured physical activity captured by 24-hour actigraphy, and sleep, captured objectively by overnight actigraphy and subjectively self-reported sleep measures. The investigators hypothesize that weight stigma causes decrements in health behaviors (e.g., sleep, eating, and physical activity) in everyday life.

Study Overview

• Status: Completed
• Conditions: Obesity
• Intervention / Treatment: Behavioral: Weight stigma intervention

• Study Type: Interventional
• Enrollment (Actual): 330
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Los Angeles, California, United States, 90034
      • University of California, Los Angeles

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Age 18+
2. English-speaking
3. BMI greater than or equal to 28

Exclusion Criteria:

1. Major mental disorder including eating disorder, mood disorder, schizophrenia, PTSD
2. Recent (<1 year) diagnosis of major physical conditions that limit physical movement
3. Recent (<1 year) diagnosis of sleep disorder
4. Allergy to any of the foods in the food buffet

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Experimental (Weight Stigma) Arm; Participants undergoing the experimental (Weight Stigma) arm are exposed to an interaction partner (a trained confederate) who endorses anti-fat attitudes. Prior to their interaction, participants exchange a "Getting to Know You Questionnaire" with the confederate, where the confederate endorses anti-fat attitudes. During their interaction with the confederate, participants are told they will be completing consumer rating tasks with another participant in the study. During the ostensible consumer rating task, participants in the experimental condition rate items such as a diet magazine, body sunscreen, running shoes, and a size small T-shirt labeled as size large to bolster the weight stigma manipulation.	Behavioral: Weight stigma intervention; Those undergoing the weight stigma manipulation will be exposed to an interaction partner (a trained confederate) who will endorse anti-fat attitudes. The purpose of this interaction is to examine the causal effects of weight stigma on eating behaviors, physical activity, and sleep.
No Intervention: Control Arm; Participants undergoing the control arm are also exposed to an interaction partner (a trained confederate) who does not endorse anti-fat attitudes. Prior to their interaction, participants exchange a "Getting to Know You Questionnaire" with the confederate; however, the confederate does not endorse anti-fat attitudes. During their interaction with the confederate, participants are told they will be completing consumer rating tasks with another participant in the study. During the ostensible consumer rating task, participants in the control condition rate items such as an interior design magazine, face sunscreen, regular (non-running) shoes, and a size large T-shirt correctly labeled as size large to avoid weight stigma.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Hyperpalatable Food Intake	Hyperpalatable food intake will initially be measured in grams and then converted into kilocalories. The food will consist of the following items: chocolate chip cookies, M&Ms, potato chips, and Sprite. These foods were chosen because processed foods, added sugars, refined grains, starchy vegetables, and sugar sweetened beverages are foods to avoid according to the 2019 American Diabetes Association Nutrition Consensus Report and are high in carbohydrates and glycemic index.	Hyperpalatable food intake will be measured directly after the intervention, on average 10 minutes later.
Change in Self-reported Dietary Intake	Dietary intake data for food recalls will be collected and analyzed using the Automated Self-Administered 24-hour (ASA24) Dietary Assessment Tool developed by the National Cancer Institute, Bethesda, MD. The primary eating outcome for the food diaries will be kilocalories.	Change in self-reported dietary intake will be assessed by measuring self-reported dietary intake 72 hours before the intervention as part of the baseline, and 72 hours after the intervention.
Change in Physical Activity	Physical activity, quantified as Metabolic Equivalent of Task (MET) units, will be assessed using ActivPAL4 actigraphs.	Change in physical activity will be assessed by measuring physical activity for 72 hours before the intervention as part of the baseline, and 72 hours after the intervention.
Change in Sleep Duration	Change in sleep duration will be assessed using an Actiwatch-2 (Philips Respironics). Data will be captured in 30-second epochs and validated. Actiware 6.0.9 software algorithms will be used to estimate sleep parameters with the following sleep/wake algorithm: D = A-2*(1/25) + A1*(1/5) + A*(1) + A + 1*(1/5) + A + 2*(1/25), where AX = accelerometer activity for that minute.	Change in sleep duration will be assessed by measuring sleep duration for three days before the intervention as part of the baseline, and three days after the intervention.
Change in Self-reported Sleep Quality	Participants will respond to a single item assessing past night's sleep quality, with response options ranging from 1 (very bad) to 4 (very good). Change in subjective sleep quality will be calculated by taking the difference of the item score pre- and post-intervention. The possible minimum for change in self-reported sleep quality is -3 and the possible maximum is 3. In this difference score, higher scores indicate improvements in sleep quality from baseline to post.	Change in self-reported sleep quality will be assessed by measuring self-reported sleep quality during the mornings of the first 72 hour baseline period before the intervention, and in the mornings of the 72 hour period after the intervention.
Change in Sleep Onset Latency	Change in sleep onset latency will be assessed using an Actiwatch-2 (Philips Respironics). Data will be captured in 30-second epochs and validated. Actiware 6.0.9 software algorithms will be used to estimate sleep parameters with the following sleep/wake algorithm: D = A-2*(1/25) + A1*(1/5) + A*(1) + A + 1*(1/5) + A + 2*(1/25), where AX = accelerometer activity for that minute. Sleep onset is operationalized as after 10 consecutive minutes of D ≤ 40 (as D > 40 indicates participants are awake).	Change in sleep onset latency will be assessed by measuring sleep onset latency for three days before the intervention as part of the baseline, and three days after the intervention.
Change in Sleep Efficiency	Change in sleep efficiency will be assessed using an Actiwatch-2 (Philips Respironics). Data will be captured in 30-second epochs and validated. Actiware 6.0.9 software algorithms will be used to estimate sleep parameters with the following sleep/wake algorithm: D = A-2*(1/25) + A1*(1/5) + A*(1) + A + 1*(1/5) + A + 2*(1/25), where AX = accelerometer activity for that minute. The possible minimum value is -100 and the possible maximum value is 100. Higher scores indicate better sleep efficiency.	Change in sleep efficiency will be assessed by measuring sleep efficiency for three days before the intervention as part of the baseline, and three days after the intervention.

Collaborators and Investigators

• Sponsor: University of California, Los Angeles
• Collaborators: University of California, San Francisco; Miami University
• Investigators: Principal Investigator: A. Janet Tomiyama, Ph.D., University of California, Los Angeles

Study record dates

Study Major Dates

• Study Start (Actual): April 28, 2022
• Primary Completion (Actual): August 3, 2024
• Study Completion (Actual): August 3, 2024

Study Registration Dates

• First Submitted: May 25, 2022
• First Submitted That Met QC Criteria: May 27, 2022
• First Posted (Actual): June 2, 2022

Study Record Updates

• Last Update Posted (Actual): January 20, 2026
• Last Update Submitted That Met QC Criteria: December 29, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: Exercise; Sleep; Eating; Actigraphy; Ecological Momentary Assessment; Weight Prejudice; Diet Records
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Overweight; Pathological Conditions, Signs and Symptoms; Behavior; Nutritional and Metabolic Diseases; Signs and Symptoms; Social Behavior; Prejudice; Obesity; Motor Activity; Weight Prejudice
• Other Study ID Numbers: 21-000460

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No