Randomized Controlled Experiment of Dieting in Pairs

Not Applicable

Completed

• Conditions: Dietary Modification
• Interventions: Behavioral: Mixed Diet Condition; Behavioral: Both Diet Condition

• Registration Number: NCT02898844
• Lead Sponsor: A. Janet Tomiyama

Brief Summary

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

Detailed Description

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.

Study Timeline

• Study Start: 2013-10
• Primary Completion: 2014-12
• Study Completion: 2014-12
• Status Verified: 2016-09
• Study First Submitted: 2016-09-08
• Study First Submitted QC: 2016-09-12
• Last Update Submitted: 2016-09-12
• Study First Posted: 2016-09-13
• Last Update Posted: 2016-09-13

Recruitment & Eligibility

• Status: COMPLETED
• Sex: Female
• Target Recruitment: 164

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Mixed Diet Condition	Mixed Diet Condition	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.
Both Diet Condition	Both Diet Condition	Low-calorie diet: Both roommates in each pair were randomly assigned to a 1200-calorie/day diet.

Primary Outcome Measures

Name	Time	Method
Weight loss measured via pounds	~3 days after end of 3-week manipulation
Diet adherence measured via daily calorie counts	up to 3-week
Psychological well-being measured via electronic questionnaires	~3 days after end of 3-week manipulation

Secondary Outcome Measures

Name	Time	Method
Cortisol measured via 2 days diurnal cortisol	1 day after end of 3-week manipulation