Randomized Controlled Experiment of Dieting in Pairs

Study Overview
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Brief Summary
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This study examined how dieting with a partner affects weight loss, diet adherence, psychological well-being, and cortisol.

Detailed Description
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The goal of this study was to understand how different types of diet buddy systems affect diet success and outcomes related to dieting. Pairs of non-romantic cohabiting female dyads (i.e. roommates) were randomly assigned to one of the following three-week manipulations: (a) neither roommate dieted, (b) one roommate was assigned to a 1200-calorie/day diet and the other ate normally, (c) both roommates were assigned to a 1200-calorie/day diet. Both pre- and post diet, participants were weighted and measured, filled out psychological questionnaires, and provided two days of diurnal salivary cortisol samples. During the three-week manipulation period, participants who were assigned to diet recorded all calories consumed on each day. This study tested whether dieting in a pair would lead to improved diet outcomes in terms of adherence and weight loss, changes in psychological well-being, and changes in cortisol.

Official Title
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Randomized Controlled Experiment of Dieting in Pairs

Conditions
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Dietary Modification

Intervention / Treatment
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* Behavioral: Mixed Diet Condition
* Behavioral: Both Diet Condition


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Female Over 18 years of age Interested in dieting in the coming 12 months self-reported BMI over 18.5 < 5 kg weight change in previous 3 months Have a university meal plan Have a roommate also willing/eligible to participate Exclusion Criteria: Recent/current history of major medical disorder Pregnancy/lactation History of eating disorder Use of lipid-lowering medications Use of weight-altering/metabolism-altering medications Smoking

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Control Condition<br>Neither roommate dieted. | |
| Experimental: Mixed Diet Condition<br>Low-calorie diet: One roommate in each pair was randomly assigned to a 1200-calorie/day diet, while the other roommate was instructed to eat normally. | Behavioral: Mixed Diet Condition<br>* One roommate dieted and the other ate normally.<br>|
| Experimental: Both Diet Condition<br>Low-calorie diet: Both roommates in each pair were randomly assigned to a 1200-calorie/day diet. | Behavioral: Both Diet Condition<br>* Both roommates dieted.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Psychological well-being measured via electronic questionnaires |  |  3 days after end of 3-week manipulation | 
| Weight loss measured via pounds |  |  3 days after end of 3-week manipulation | 
| Diet adherence measured via daily calorie counts |  | up to 3-week | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cortisol measured via 2 days diurnal cortisol |  | 1 day after end of 3-week manipulation | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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dieting, dyads, psychological well-being, weight loss, cortisol