Evaluation of a Letter Intervention Promoting a Plant-based Diet
1 other identifier
interventional
11,234
1 country
1
Brief Summary
The researchers' mission is to promote healthier eating behavior and to reduce costs associated with healthcare. The purpose of this study is to evaluate the effects of mailing randomly selected participants a letter promoting a plant-based diet. Depending on the experimental condition, participants may additionally receive a free documentary, Forks Over Knives, and they may also get letters which use commitment- or prevention-focused messages to encourage watching the documentary and changing their eating behavior. The researchers hypothesize that receiving the documentary will be associated with lower insurance claims and improved health outcomes one and two years later. The researchers also hypothesize that using either commitment- or prevention-focused messages will also contribute to lower insurance claims and improved health outcomes compared to experimental conditions where materials did not include these messages. This study will help the researchers design evidence-supported programs that can improve people's health.
Trial Health
Trial Health Score
Automated assessment based on enrollment pace, timeline, and geographic reach
participants targeted
Target at P75+ for not_applicable cardiovascular-diseases
Started Jun 2019
Typical duration for not_applicable cardiovascular-diseases
1 active site
Health score is calculated from publicly available data and should be used for screening purposes only.
Trial Relationships
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Study Timeline
Key milestones and dates
First Submitted
Initial submission to the registry
March 14, 2019
CompletedFirst Posted
Study publicly available on registry
March 19, 2019
CompletedStudy Start
First participant enrolled
June 20, 2019
CompletedPrimary Completion
Last participant's last visit for primary outcome
June 30, 2020
CompletedStudy Completion
Last participant's last visit for all outcomes
June 30, 2022
CompletedResults Posted
Study results publicly available
September 7, 2023
CompletedMay 20, 2025
May 1, 2025
1 year
March 14, 2019
April 1, 2022
May 1, 2025
Conditions
Keywords
Outcome Measures
Primary Outcomes (7)
Medical Cost in US Dollars From One Year Before to One Year After Intervention
Total annual amount of medical and pharmacy costs (sum) as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Lower costs is the desirable outcome.
2 years
Number of Visits From One Year Before to One Year After Intervention
Total number of primary care physician and specialist visits (sum) as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Fewer visits is the desirable outcome.
2 years
Number of Prescriptions From One Year Before to One Year After Intervention
Total number of prescriptions (fills) as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Fewer prescriptions is the desirable outcome.
2 years
Number of Unique Prescribed Medication From One Year Before to One Year After Intervention
Total number of unique prescribed medication in the past year as reported by Geisinger Health Plan. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Less unique prescribed medication is the desirable outcome.
2 years
Body Mass Index From One Year Before to One Year After Intervention
Taken from annual checkup with primary care provider. Computed from height (in meters) and weight (in kilograms) data with the formula kilograms/meters\^2. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. A body mass index between the range of 18.5 to 25 is the desirable outcome.
2 years
Systolic Blood Pressure From One Year Before to One Year After Intervention
Taken from annual checkup with primary care provider. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Systolic blood pressure that is 120 millimeters of mercury (mmHg) or less is the desirable outcome.
2 years
Diastolic Blood Pressure From One Year Before to One Year After Intervention
Taken from annual checkup with primary care provider. General linear models are used to model change between the data from the year before the intervention and the data from one year after intervention. Systolic blood pressure that is 80 millimeters of mercury (mmHg) or less is the desirable outcome.
2 years
Secondary Outcomes (19)
Triglyceride Levels From One Year Before to One Year After Intervention
2 years
Low-density Lipoprotein (LDL) Levels From One Year Before to One Year After Intervention
2 years
Five Years Before to Two Years After Intervention in Depressed Mood and Anhedonia as Assessed by the Patient Health Questionnaire-2 (PHQ-2) (Extended Time Frame)
7 years
Hemoglobin A1c (hbA1c) From Five Years Before to Two Years After Intervention (Extended Time Frame)
7 years
Low-density Lipoprotein/High-density Lipoprotein (LDL/HDL) Ratios From Five Years Before to Two Years After Intervention (Extended Time Frame)
7 years
- +14 more secondary outcomes
Study Arms (14)
No contact control
NO INTERVENTIONParticipants are not contacted.
Letter
EXPERIMENTALParticipants are only contacted through a letter with a personal testimonial.
Link and no nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and no nudges.
Link and commitment nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and a commitment nudge.
Link and prevention nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and a prevention nudge.
Link and both nudges
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and both commitment and prevention nudges.
DVD and no nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and no behavioral nudges.
DVD and commitment nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and a commitment nudge.
DVD and prevention nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and a prevention nudge.
DVD and both nudges
EXPERIMENTALParticipants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and both commitment and prevention nudges.
Link and DVD and no nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and no behavioral nudges.
Link and DVD and commitment nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and a commitment nudge.
Link and DVD and prevention nudge
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and a prevention nudge.
Link and DVD and both nudges
EXPERIMENTALParticipants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and both commitment and prevention nudges.
Interventions
Participants will receive a letter promoting a plant-based diet. This letter will feature a personal testimonial about the benefits of a plant-based diet. Presenting this information to participants might encourage them to make behavioral changes to improve their health.
Participants will be mailed the documentary Forks Over Knives, which provides scientific arguments promoting a plant-based and whole foods diet. The behavioral effect of this documentary comes from watching the documentary and potentially choosing to order a free cookbook (participants are given this opportunity in the letter accompanying the documentary). The effect of the diet itself is not a central part of the intervention, as people can choose to adopt or not adopt any part of the diet.
At the end of the letter promoting a plant-based diet, participants will be asked to write dates and personal signatures committing to watching the documentary. They will be asked to mail back this written commitment. Stating one's intentions to implement certain behavior is meant to increase the likelihood of follow-up behavior. This request might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
As part of the letter promoting a plant-based diet, one paragraph will describe the risks of not taking action. This phrasing reframes the status quo as contributing to future loss (e.g., costs of medication and operations). In effect, the letter encourages participants to focus on preventing this loss by taking action. This additional text might nudge more people to watch the documentary and make some behavioral changes to prevent negative health outcomes.
Eligibility Criteria
You may qualify if:
- Has two out of the three following conditions:
- Body mass index over 30
- Diagnosis of type 2 diabetes (specifically with at least one medication)
- Diagnosis of cardiovascular disease
- Has health insurance through Geisinger Health Plan (is an active member with a full 12-month enrollment in the previous year) under one of the following categories:
- Medicare with required primary care provider
- Medicaid
- Individual policy under the Affordable Care Act
- Has visited their primary care provider in the past 12 months
You may not qualify if:
- Is institutionalized
- Has active cancer, cirrhosis, renal failure, dementia, or active psychosis
- Is in the same household as another selected participant
Contact the study team to confirm eligibility.
Sponsors & Collaborators
- Geisinger Cliniclead
Study Sites (1)
Geisinger Health System
Danville, Pennsylvania, 17822, United States
Related Publications (2)
Milkman KL, Beshears J, Choi JJ, Laibson D, Madrian BC. Using implementation intentions prompts to enhance influenza vaccination rates. Proc Natl Acad Sci U S A. 2011 Jun 28;108(26):10415-20. doi: 10.1073/pnas.1103170108. Epub 2011 Jun 13.
PMID: 21670283BACKGROUNDTversky A, Kahneman D. The framing of decisions and the psychology of choice. Science. 1981 Jan 30;211(4481):453-8. doi: 10.1126/science.7455683.
PMID: 7455683BACKGROUND
Related Links
MeSH Terms
Conditions
Condition Hierarchy (Ancestors)
Limitations and Caveats
Due to limited data access, only information related to mailing and the outcomes were given to the researchers.
Results Point of Contact
- Title
- Amir Goren
- Organization
- Geisinger Clinic
Study Officials
- PRINCIPAL INVESTIGATOR
Amir Goren, PhD
Program Director
- STUDY DIRECTOR
Henri Carlo Y Santos, PhD
Post-doctoral Fellow
- STUDY DIRECTOR
Christopher Chabris, PhD
Professor
- STUDY DIRECTOR
Michelle N Meyer, PhD, JD
Assistant Professor
- STUDY DIRECTOR
Allison Hess, BS
Vice President
Publication Agreements
- PI is Sponsor Employee
- Yes
Study Design
- Study Type
- interventional
- Phase
- not applicable
- Allocation
- RANDOMIZED
- Masking
- TRIPLE
- Who Masked
- PARTICIPANT, CARE PROVIDER, OUTCOMES ASSESSOR
- Masking Details
- Participants, care providers, and outcomes assessors will not know the participant's arm. Insurance claims data and medical health records will be used (after all identifying information is removed).
- Purpose
- SUPPORTIVE CARE
- Intervention Model
- FACTORIAL
- Sponsor Type
- OTHER
- Responsible Party
- PRINCIPAL INVESTIGATOR
- PI Title
- Program Director
Study Record Dates
First Submitted
March 14, 2019
First Posted
March 19, 2019
Study Start
June 20, 2019
Primary Completion
June 30, 2020
Study Completion
June 30, 2022
Last Updated
May 20, 2025
Results First Posted
September 7, 2023
Record last verified: 2025-05
Data Sharing
- IPD Sharing
- Will share
- Shared Documents
- STUDY PROTOCOL, SAP, ANALYTIC CODE
- Time Frame
- The data will become available upon publication and will be available as long as the Open Science Framework hosts the data.
- Access Criteria
- The data on the Open Science Framework will be open to anyone requesting that information.
Data with no personally identifiable information will be made available to other researchers on the Open Science Framework for transparency. This will include preregistered hypotheses, analysis plan and code, and the essential data needed to replicate the analysis that yielded reported findings.