Effectively promoting healthy
food choices
The effect of taxing unhealthy food items and healthy eating calls
in the form of a descriptive norm on the healthiness of food
purchases
Thesis defense
Table of Contents
1. Introduction
2. Theoretical Background
3. Conceptual Model
4. Methodology
5. Results
6. Theoretical Implications
Introduction
Background problem
High overweight and obesity rates
Negatively affects personal well-being
Major medical costs for society
Overweight and obesity issues are primarily caused by the overconsumption
of calories
-
the average daily calorie intake of American consumers increased with 600
calories from 1970 to 2007
Theoretical Background
Interventions may help consumers to interchange unhealthier
options for healthier alternatives
Intervention
Effect
Taxing unhealthy food items
Positive cross-price elasticity
Healthy eating calls in the form of a descriptive
norm
Social proof heuristic
Taxing unhealthy food items and healthy eating
Conceptual Model
Hypothesis 1. Taxing unhealthy food items
increases the healthiness of the purchases in the
target categories.
Hypothesis 2. Taxing unhealthy food items
increases the healthiness of the purchases in the
overall shopping basket.
Hypothesis 3. Healthy eating calls in the form of a
descriptive norm increase the healthiness of the
purchases in the target categories.
Hypothesis 4. Healthy eating calls in the form of a
descriptive norm increase the healthiness of the
purchases in the overall shopping basket.
Hypothesis 5. The effect of taxing unhealthy food
items on the healthiness of the purchases in the
target categories is more pronounced in the
presence of healthy eating calls in the form of a
descriptive norm.
Hypothesis 6. The effect of taxing unhealthy food
Methodology
Participants were recruited via Amazon Mechanical Turk and were asked
to purchase groceries in 25 different product categories
Randomized between-subjects design:
-
two levels of taxes on relatively unhealthy food items (25% versus no) x
two levels of healthy eating calls in the form of a descriptive norm on
relatively healthy food items (yes versus no)
Condition
N
No Intervention
73
Taxing
60
Healthy Eating Call
70
Study Design
o
Tax of 25%: on the relatively unhealthiest product
in the categories mayonnaise, cola, chips, pasta
sauce, and spam classic meat
Measurement of Dependent Variables
Variable
Measurement
The healthiness of the purchases
in the target categories
Within each target category:
• Two products with the lowest number of calories (per
100 grams): relatively healthy choice (0)
• Two products with the highest number of calories (per
100 grams): relatively unhealthy choice (1)
The healthiness of the purchases
Results
• Factorial analysis of variance (ANOVA)
• Results were essentially identical when including control variables
Predictors
F -value
p- value
F -value p- value
Taxing unhealthy food items
.04
.85
.06
.81
Healthy eating calls in the form of a descriptive
norm
44.35
.00**
9.70
.00**
Taxing unhealthy food items × healthy eating calls
in the form of a descriptive norm
.09
.76
.24
.63
* p < .05; ** p < .01
df = 1
Healthiness of target
category
Healthiness of overall
shopping basket
Dependent variables
Factorial ANOVA for the influence of taxing unhealthy food items and healthy eating calls in the
form of a descriptive norm on the healthiness of the purchases in the target categories and the overall
Follow-up Analysis - Covariates
Predictors
B
SE
t
p
B
SE
t
p
Taxing unhealthy food items
-.01
.01
-.86
.39
-17.08
28.18
-.61
.55
Healthy eating calls in the form of a descriptive
norm
-.05
.01
-3.64 .00**
-58.17
28.51
-2.04
.04*
Age
.00
.00
1.37
.17
6.69
3.01
2.18
.03*
Gender
-.01
.03
-.45
.65
-28.06
56.40
-.50
.62
Education
.01
.01
.54
.59
27.12
28.11
.97
.34
BMI
-.00
.00
-1.64
.10
1.64
4.97
.33
.74
Hunger level
-.01
.01
-.48
.63
-8.98
25.94
-.35
.73
Dietary restrictions (No = 0, Yes = 1)
.01
.03
.35
.73
-55.97
68.38
-.82
.41
Health consciousness
-.09
.02
-5.10 .00**
-202.57
35.65
-5.68 .00**
Self-regulatory focus
.06
.02
3.28 .00**
97.91
36.97
2.65 .01**
* p < .05; ** p < .01
df = 255
Healthiness of the purchases in the target categories
Healthiness of the purchases in the overall
shopping basket
Regression analyses for taxing unhealthy food items, healthy eating calls in the form of a descriptive norm, age, gender, education, BMI, hunger level,
dietary restrictions, health consciousness and self-regulatory focus on the healthiness of the purchases in the target categories and overall shopping basket
Healthiness of the purchases in the overall shopping
basket Healthy eating calls
in the form of a descriptive norm Taxing unhealthy food items Healthiness of the purchases in the target categories
No significant effect
Positive significant effect
Negative significant effect
Self-regulatory focus Health consciousness
Follow-up Analysis – Health Consciousness
Predictors
B
SE
t
p
B
SE
t
p
Taxing unhealthy food items
-.01 .01
-.85 .39
-13.07 28.11
-.46 .64
Healthy eating calls in the form of a descriptive
norm
-.05 .01 -4.11 .00**
-71.81 28.04 -2.56 .01*
Taxing unhealthy food items × healthy eating calls
in the form of a descriptive norm
-.00 .01
-.03 .98
-5.89 28.12
-.21 .83
Health consciousness
-.06 .02 -3.79 .00** -155.14 33.40 -4.65 .00**
Health consciousness × taxing unhealthy food
items
.00 .02
.19 .85
9.01 33.78
.27 .79
Health consciousness × healthy eating calls in the
form of a descriptive norm
.01 .02
.90 .37
23.87 33.32
.72 .47
Health consciousness × healthy eating calls in the
form of a descriptive norm × taxing unhealthy
food items
.01 .02
.72 .47
19.87 33.70
.59 .56
* p < .05; ** p < .01
df = 261
Assessing the interaction effect of health consciousnesss with taxing unhealthy food items and healthy
eating calls in the form of a descriptive norm
Dependent variables
Healthiness of the
purchases in the target
categories
Healthiness of the purchases
in the overall shopping
Theoretical Implications
Healthy eating calls in the form of a descriptive norm is an
effective intervention
Possible explanations for why this research did not find a
significant effect of taxing unhealthy food items
Starting point for fellow researchers to examine how synergy
effects of health interventions may be created
Results showed that when values of self-regulatory focus are
Limitations and Future Research
Limitations
Future Research
Relatively low financial incentive ($0.20) participants
might fill in survey as quickly as possible
Longer time frame
Food purchases in a restricted food environment
Broader food environment
Might be a difference between the effectiveness of
interventions in an online and offline environment
Offline environment
Healthiness of the food purchases was judged on
calories
Energy and nutritional quality
This study did not consider dynamics of a consumer’s
shopping trip
Dynamics of a consumer’s shopping trip
Self-regulatory was measured by self-ratings
Priming self-regulatory focus
Examine differences in the effectiveness of healthy
eating calls and healthy eating calls in the form of a
descriptive norm
Practical Implications
Most food purchases are made in the supermarket
According to this study, healthy eating calls in the form of a descriptive norm increase
the healthiness of food purchases
implementing this intervention in (online) supermarkets is potentially effective in
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