Randomized Controlled Experiment of Dieting in Pairs

A. Janet Tomiyama

Status: Completed

Conditions: Dietary Modification

Treatments: Behavioral: Both Diet Condition; Behavioral: Mixed Diet Condition

Study type: Interventional

Funder types: Other

Identifiers

NCT02898844

13-000666

Details and patient eligibility

About

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

Full 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.

Enrollment: 164 patients

Sex: Female

Ages: 18+ years old

Volunteers: Accepts Healthy Volunteers

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

Trial design

Primary purpose: Basic Science

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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164 participants in 3 patient groups

Control Condition

No Intervention group

Description:

Neither roommate dieted.

Mixed Diet Condition

Experimental group

Description:

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.

Treatment:

Behavioral: Mixed Diet Condition

Both Diet Condition

Experimental group

Description:

Low-calorie diet: Both roommates in each pair were randomly assigned to a 1200-calorie/day diet.

Treatment:

Behavioral: Both Diet Condition