Enhanced Broccoli Consumption After a Liking Norm and Vegetable Variety Message: Effects After a 24 Hour Delay.

Encouraging individuals to eat vegetables is difficult. However, recent evidence suggests that using social-based information might help. For instance, it has been shown that if people think that others are eating lots of fruit and vegetables, that they will consume more of these foods to match the 'norm'. The purpose of this study was to determine whether a liking social norm (information about how much others like vegetables) would be effective at encouraging people to eat more vegetables and to examine whether these effects are sustained beyond initial exposure (i.e. whether the effect of the norm persists on food selection 24 hours alter).

Study Overview

• Status: Completed
• Conditions: Eating Behaviour
• Intervention / Treatment: Behavioral: Neutral Control Condition; Behavioral: Food-based Control Condition; Behavioral: Health Condition; Behavioral: Descriptive Social Norm; Behavioral: Liking Social Norm

Detailed Description

Using a 2 x 5 x 2 experimental design we investigated the effects of exposure to various messages on later food intake and whether any effects were sustained 24 hours after exposure in both low and high consumers of vegetables. There were three factors of delay (immediate food selection versus food selection 24 hours after exposure), message type (liking norm, descriptive norm, health message, food-based control, and neutral control message) and habitual consumption (low versus high). The buffet consisted of three raw vegetables, three energy-dense foods and two dips.

In this study the investigators hypothesised that a liking norm would increase the consumption of vegetables (compared to a neutral control condition) and that the effect would persist on vegetable consumption 24 hours after intital exposure to the liking norm.

• Study Type: Interventional
• Enrollment (Actual): 400
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United Kingdom
  • West Midlands
    • Birmingham, West Midlands, United Kingdom, B15 2TT
      • University of Birmingham

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 65 years (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Healthy volunteers
• Sufficiently fluent in English

Exclusion Criteria:

• Smokers
• Diabetes
• Food allergies
• Past / present depression or anxiety
• Past / present eating disorder.

Study Plan

How is the study designed?

Design Details

• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Neutral Control Condition; Message about age of University of Birmingham	Behavioral: Neutral Control Condition; Message about age of University of Birmingham
Placebo Comparator: Food-based Control Condition; Message about variety of vegetables in the world	Behavioral: Food-based Control Condition; Message about variety of vegetables in the world
Active Comparator: Health Condition; Message about the health benefits of eating vegetables	Behavioral: Health Condition; Message about the health benefits of eating vegetables
Active Comparator: Descriptive Social Norm; Message suggesting most people eat plenty of vegetables	Behavioral: Descriptive Social Norm; Message suggesting most people eat plenty of vegetables
Experimental: Liking Social Norm; Message suggesting most people like eating vegetables	Behavioral: Liking Social Norm; Message suggesting most people like eating vegetables

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Grams of vegetables consumed	8 months

Collaborators and Investigators

• Sponsor: University of Birmingham
• Collaborators: Economic and Social Research Council, United Kingdom
• Investigators: Principal Investigator: Jason M Thomas, PhD, University of Birmingham

Publications and helpful links

General Publications

• Thomas JM, Liu J, Robinson EL, Aveyard P, Herman CP, Higgs S. The Effects of Liking Norms and Descriptive Norms on Vegetable Consumption: A Randomized Experiment. Front Psychol. 2016 Mar 30;7:442. doi: 10.3389/fpsyg.2016.00442. eCollection 2016.

Study record dates

Study Major Dates

• Study Start: October 1, 2013
• Primary Completion (Actual): July 1, 2014
• Study Completion (Actual): July 1, 2014

Study Registration Dates

• First Submitted: November 24, 2015
• First Submitted That Met QC Criteria: November 27, 2015
• First Posted (Estimate): December 1, 2015

Study Record Updates

• Last Update Posted (Estimate): December 1, 2015
• Last Update Submitted That Met QC Criteria: November 27, 2015
• Last Verified: November 1, 2015

More Information

Terms related to this study

• Other Study ID Numbers: UBirmingham-SNS1