Evaluation of a Letter Intervention Promoting a Plant-based Diet

Study Overview
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Brief Summary
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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.

Detailed Description
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Note that participant selection and assignment will be done at the level of the household, but analysis of outcomes will include individual-level analysis. This analytic decision was made because the researchers assume that the intervention may potentially affect other members of the household. While one person in a household will be selected for matching the eligibility criteria, the mailed materials will be addressed to all adult members of the household (defined as adults 18+ who are the spouse or child of the selected member) who are members of the Geisinger Health Plan. Outcome data will be pulled from all adult members of the household who have data through the Geisinger Health Plan. The researchers will analyze the data using standard survey research analyses methods, including computing bivariate correlations, using general linear models, using non-parametric models for non-normally distributed insurance data, and entering variables as independent predictors in regression models to attempt to predict desired outcomes. The researchers will also use multilevel models to account for household- and individual-level data. The analysis of primary outcomes will focus on data one year after the intervention begins. Follow-up analysis on secondary outcomes will be conducted two years after the intervention begins. The researchers will conduct separate analyses of the selected participant (i.e., the individual who met the eligibility criteria) and other members of that participant's household. This will test whether there are any spillover effects of the intervention to other people in the household. For clarity in this record, any discussion of sample size and participants refers to households, as this is the primary level for participant selection and assignment.

Official Title
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Evaluation of a Letter Intervention Among At-risk Adults Promoting a Plant-based Diet Using a Combination of Provider Testimonials, the Forks Over Knives Documentary, and Commitment- or Prevention-focused Behavioral Nudges

Conditions
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Cardiovascular Diseases, Diabetes Mellitus, Obesity

Intervention / Treatment
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* Behavioral: Personal testimonial
* Behavioral: Forks Over Knives Documentary
* Behavioral: Commitment nudge
* Behavioral: Prevention nudge


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 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 Exclusion Criteria: Is institutionalized Has active cancer, cirrhosis, renal failure, dementia, or active psychosis Is in the same household as another selected participant

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Supportive Care
Allocation: Randomized
Intervention Model: Factorial Assignment
Interventional Model Description: One group of participants will not be contacted at all (n = 6200). One group will only received a letter promoting a plant-based diet (n = 2200). Twelve groups (n = 550 for each group) will receive the letter promoting a plant-based diet, along with the Forks Over Knives documentary. The documentary will be delivered through 3 different methods, and the accompanying letter will contain 4 different combinations of behavioral nudges. 1 primary control group (no contact) 1 group contacted by letter 3 groups (documentary distribution: online link, DVD, online link + DVD) x 4 groups (behavioral nudges in the letter: no nudge, commitment nudge, prevention nudge, commitment and prevention nudges) Note: The control group size is an estimate of number of participants who match the eligibility criteria but were not randomly assigned to an experimental group.
Masking: Triple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: No contact control<br>Participants are not contacted. | |
| Experimental: Letter<br>Participants are only contacted through a letter with a personal testimonial. | Behavioral: Personal testimonial<br>* 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.<br>|
| Experimental: Link and no nudge<br>Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and no nudges. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>|
| Experimental: Link and commitment nudge<br>Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and a commitment nudge. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Commitment nudge<br>* 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.<br>|
| Experimental: Link and prevention nudge<br>Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and a prevention nudge. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Prevention nudge<br>* 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.<br>|
| Experimental: Link and both nudges<br>Participants are sent the Forks Over Knives documentary online link and a letter with a personal testimonial and both commitment and prevention nudges. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Commitment nudge<br>* 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.<br>Behavioral: Prevention nudge<br>* 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.<br>|
| Experimental: DVD and no nudge<br>Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and no behavioral nudges. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>|
| Experimental: DVD and commitment nudge<br>Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and a commitment nudge. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Commitment nudge<br>* 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.<br>|
| Experimental: DVD and prevention nudge<br>Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and a prevention nudge. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Prevention nudge<br>* 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.<br>|
| Experimental: DVD and both nudges<br>Participants are sent the Forks Over Knives documentary DVD and a letter with a personal testimonial and both commitment and prevention nudges. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Commitment nudge<br>* 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.<br>Behavioral: Prevention nudge<br>* 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.<br>|
| Experimental: Link and DVD and no nudge<br>Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and no behavioral nudges. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>|
| Experimental: Link and DVD and commitment nudge<br>Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and a commitment nudge. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Commitment nudge<br>* 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.<br>|
| Experimental: Link and DVD and prevention nudge<br>Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and a prevention nudge. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Prevention nudge<br>* 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.<br>|
| Experimental: Link and DVD and both nudges<br>Participants are sent the Forks Over Knives documentary online link and DVD and a letter with a personal testimonial and both commitment and prevention nudges. | Behavioral: Personal testimonial<br>* 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.<br>Behavioral: Forks Over Knives Documentary<br>* 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.<br>Behavioral: Commitment nudge<br>* 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.<br>Behavioral: Prevention nudge<br>* 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.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 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 Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Triglyceride Levels From One Year Before to One Year After Intervention | One component of cholesterol, used if data is on health record. A triglyceride level of 150 milligrams per deciliter (mg/dl) or lower is the desirable outcome. | 2 years | 
| Low-density Lipoprotein (LDL) Levels From One Year Before to One Year After Intervention | One component of cholesterol, used if data is on health record. An LDL level of 100 milligrams per deciliter (mg/dl) or lower is the desirable outcome. | 2 years | 
| High-density Lipoprotein (HDL) Levels From One Year Before to One Year After Intervention | One component of cholesterol, used if data is on health record. An HDL level of 60 milligrams per deciliter (mg/dl) or higher is the desirable outcome. | 2 years | 
| Low-density Lipoprotein/High-density Lipoprotein (LDL/HDL) Ratios From One Year Before to One Year After Intervention | Computed as the ratio of LDL/HDL. An LDL/HDL ratio of 3 or less for men and 2.5 or less for women is the desirable outcome. | 2 years | 
| Hemoglobin A1c (hbA1c) From One Year Before to One Year After Intervention | Test for diabetes, used if data is on health record. Percentage score reflects blood-glucose levels. An hbA1c level of 5.7% or lower is the desirable outcome. | 2 years | 
| Values From One Year Before to One Year After Intervention of Depressed Mood and Anhedonia as Assessed by the Patient Health Questionnaire-2 (PHQ-2) | Assesses depressed mood and anhedonia in the past two weeks; used if data is on health record. The sum of two items (each scored 0-3) is computed with a total score range of 0-6. A lower score is the desired outcome. | 2 years | 
| Medical Cost in US Dollars From Five Years Before to Two Years After Intervention (Extended Time Frame) | Total annual amount of medical and pharmacy costs (sum) as reported by Geisinger Health Plan. Lower costs is the desirable outcome. | 7 years | 
| Number of Visits From Five Years Before to Two Years After Intervention (Extended Time Frame) | Total number of primary care physician and specialist visits (sum) as reported by Geisinger Health Plan. Fewer visits is the desirable outcome. | 7 years | 
| Number of Prescriptions From Five Years Before to Two Years After Intervention (Extended Time Frame) | Total number of prescriptions (standard unit is prescription per number of days supplied) as reported by Geisinger Health Plan. Fewer prescriptions is the desirable outcome. | 7 years | 
| Number of Unique Prescribed Medication From Five Years Before to Two Years After Intervention (Extended Time Frame) | Total number of unique prescribed medication in the past year as reported by Geisinger Health Plan. Less unique prescribed medication is the desirable outcome. | 7 years | 
| Body Mass Index From Five Years Before to Two Years After Intervention (Extended Time Frame) | Taken from annual checkup with primary care provider. Computed from height (in meters) and weight (in kilograms) data with the formula kilograms/meters^2. A body mass index between the range of 18.5 to 25 is the desirable outcome. | 7 years | 
| Systolic Blood Pressure From Five Years Before to Two Years After Intervention (Extended Time Frame) | Taken from annual checkup with primary care provider. Systolic blood pressure that is 120 millimeters of mercury (mmHg) or less is the desirable outcome. | 7 years | 
| Diastolic Blood Pressure From Five Years Before to Two Years After Intervention (Extended Time Frame) | Taken from annual checkup with primary care provider. Systolic blood pressure that is 80 millimeters of mercury (mmHg) or less is the desirable outcome. | 7 years | 
| Triglyceride Levels From Five Years Before to Two Years After Intervention (Extended Time Frame) | One component of cholesterol, used if data is on health record. A triglyceride level of 150 milligrams per deciliter (mg/dl) or lower is the desirable outcome. | 7 years | 
| Low-density Lipoprotein (LDL) Levels From Five Years Before to Two Years After Intervention (Extended Time Frame) | One component of cholesterol, used if data is on health record. An LDL level of 100 milligrams per deciliter (mg/dl) or lower is the desirable outcome. | 7 years | 
| High-density Lipoprotein (HDL) Levels From Five Years Before to Two Years After Intervention (Extended Time Frame) | One component of cholesterol, used if data is on health record. An HDL level of 60 milligrams per deciliter (mg/dl) or higher is the desirable outcome. | 7 years | 
| Low-density Lipoprotein/High-density Lipoprotein (LDL/HDL) Ratios From Five Years Before to Two Years After Intervention (Extended Time Frame) | Computed as the ratio of LDL/HDL. An LDL/HDL ratio of 3 or less for men and 2.5 or less for women is the desirable outcome. | 7 years | 
| Hemoglobin A1c (hbA1c) From Five Years Before to Two Years After Intervention (Extended Time Frame) | Test for diabetes, used if data is on health record. Percentage score reflects blood-glucose levels. An hbA1c level of 5.7% and below is the desirable outcome. | 7 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) | Assesses depressed mood and anhedonia in the past two weeks; used if data is on health record. The sum of two items (each scored 0-3) is computed with a total score range of 0-6. A lower score is the desired outcome. | 7 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Plant-based diet, Behavioral nudge, Mail distribution, Randomized controlled trial, Insurance claims, Chronic disease, Letter-based intervention, Health behaviors, Prevention focus, Loss framing, Commitment, Provider testimonial