Socioeconomic Position and the Effect of Portion Size Reduction: a 1-day Dietary Behaviour Experimental Study
Phase: NA
Conditions: Diet, Healthy, Eating Behavior, Obesity
Sponsor: University of Liverpool

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SEP and portion size effect protocol 
STUDY PROTOCOL 
Study title: Socioeconomic position and the effect of portion size reduction: a 1-day dietary 
behaviour experimental study 
Short title: SEP and portion size effect 
Investigators: Dr Tess Langfield  
Dr Lucile Marty 
 
 
Dr Andrew Jones 
Dr Eric Robinson 
Funder: European Research Council 
TABLE OF CONTENTS 
 
1. 
BACKGROUND AND RATIONALE ..................................................................................................... 3 
2. 
OBJECTIVES, OUTCOMES MEASURES AND HYPOTHESES .............................................................. 4 
3. 
EXPERIMENTAL DESIGN .................................................................................................................. 4 
4. 
PARTICIPANTS AND RECRUITMENT................................................................................................ 4 
4.1. 
Recruitment ........................................................................................................................... 4 
4.2. 
Inclusion criteria .................................................................................................................... 5 
4.3. 
Exclusion criteria .................................................................................................................... 5 
5. 
METHODS ........................................................................................................................................ 6 
5.2. 
Measures ................................................................................................................................ 7 
5.2.1. 
Energy intake during test meals (breakfast, lunch, dinner and dessert) ........................ 7 
5.2.2. 
Energy intake from the snack box .................................................................................... 7 
5.2.3. 
Additional energy intake ................................................................................................... 7 
5.2.4. 
Hunger and fullness ........................................................................................................... 7 
5.2.5. 
Physical activity ................................................................................................................. 7 
5.2.6. 
Impulsivity ......................................................................................................................... 7 
5.2.7. 
Inhibition ........................................................................................................................... 8 
5.2.8. 
Portion size appropriateness ............................................................................................ 8 
5.2.9. 
Satiety responsiveness ...................................................................................................... 8 
5.2.10. 
Plate clearing tendencies .............................................................................................. 8 
5.2.11. 
Perceived food insecurity ............................................................................................. 8 
5.2.12. 
Resource availability in childhood ............................................................................... 8 
5.2.13. 
Food choice motives ..................................................................................................... 8 
5.2.14. 
Compensatory health beliefs ....................................................................................... 8 
5.2.15. 
Other questionnaire measures..................................................................................... 9 

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5.2.16. 
Demographic and socioeconomic status measures .................................................... 9 
5.2.17. 
Study experience questionnaire................................................................................... 9 
5.2.18. 
Filler measures .............................................................................................................. 9 
6. 
STUDY PROCEDURE .......................................................................................................................10 
7. 
STATISTICAL ANALYSIS ..................................................................................................................12 
7.1. 
Participant’s characteristics ................................................................................................12 
7.2. 
Variables description ...........................................................................................................12 
7.2.1. 
Primary outcome .............................................................................................................12 
7.2.2. 
Independent variables ....................................................................................................13 
7.2.3. 
Other variables ................................................................................................................14 
7.3. 
Missing data .........................................................................................................................14 
7.4. 
Primary analyses ..................................................................................................................14 
7.4.1. 
Confirmatory analyses ....................................................................................................14 
7.4.2. 
Sensitivity analyses .........................................................................................................14 
7.5. 
Secondary analyses..............................................................................................................15 
7.5.1. 
Mediation analyses .........................................................................................................15 
7.5.2. 
Hunger and fullness .........................................................................................................16 
7.5.3. 
Physical activity ...............................................................................................................16 
7.5.4. 
Study experience .............................................................................................................16 
7.6. 
Sample size...........................................................................................................................16 
8. 
REFERENCES...................................................................................................................................17 
9. 
Appendices ....................................................................................................................................21 
9.1. 
APPENDIX A: SUMMARY OF PILOT STUDIES ...........................................................................21 
9.2. 
APPENDIX B: BARRATT IMPULSIVENESS SCALE ......................................................................22 
9.3. 
APPENDIX C: SATIETY RESPONSIVENESS .................................................................................23 
9.4. 
APPENDIX D: PLATE CLEARING TENDENCIES ..........................................................................24 
9.5. 
APPENDIX E: PERCEIVED FOOD INSECURITY ...........................................................................25 
9.6. 
APPENDIX F: PERCEIVED RESOURCE AVAILABILITY IN CHILDHOOD ......................................26 
9.7. 
APPENDIX G: HEALTH AND WEIGHT CONTROL FOOD CHOICE MOTIVES ..............................27 
9.8. 
APPENDIX H: COMPENSATORY HEALTH BELIEFS ....................................................................28 
9.9. 
APPENDIX I: INTEROCEPTIVE ACCURACY SCALE .....................................................................29 
 
 
 
 

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1. BACKGROUND AND RATIONALE 
A substantial contributor to social inequalities in health is diet [1], [2]. The diet of people of lower 
socioeconomic position (SEP) is more likely to consist of foods of lower nutritional value [3], [4] and 
this may also result in passive overconsumption because portion sizes of these types of foods have 
grown in recent times [5], [6]. 
Offering larger portions compared to small portions increases energy intake. There is robust and 
reliable evidence of this phenomenon, also known as the ‘portion size effect’ (PSE) [7], [8]. It is 
unclear who is most susceptible to the PSE [9]. A recent online trial showed that the PSE on intended 
consumption of unhealthy snacks was 18-24% larger for participants of lower SEP compared to 
participants of higher SEP [10]. However, to our knowledge, no laboratory study has yet investigated 
whether people of lower SEP are more susceptible to the influence of portion size on eating 
behaviour than people of higher SEP. 
There is emerging evidence that lower SEP is associated with increased energy intake [11], [12] 
and/or inadequate energy compensation [13] but little is known about whether lower SEP is 
associated with a greater susceptibility to external influences on eating like portion size and about 
the potential mechanisms that could lead disadvantaged people to overeat in response to external 
influences like portion size. If lower SEP is associated with a greater susceptibility to the PSE then 
potential explanations include higher impulsivity, lower response inhibition, and larger portion size 
norms in people of lower vs. higher SEP [14-16]. Serving larger portions (compared to smaller 
portions) has also been shown to lead to a more pronounced increase in energy intake among 
participants with lower satiety responsiveness [17]. In addition, people of lower SEP might not 
compensate for increased energy intake because a positive energy balance is an ‘insurance’ in 
response to threatened food supply that is associated with lower SEP [18], [19] because their life 
history (e.g., exposure to harshness and unpredictability during childhood) promotes eating in the 
absence of hunger or energy need [20], [21]. A tendency to clear one’s plate has been investigated 
as a potential moderator of the PSE in a small number of studies [41-43], and those with lower SEP 
may be more likely to clear their plate despite an absence of hunger to avoid food waste (with food 
waste a higher priority for those with lower income, e.g. [44]). Higher SEP individuals may have 
stronger health motivation than lower SEP individuals [45,56]. This may reduce the impact of portion 
size on food intake because individuals with strong health motivation may be concerned about how 
much they are eating (and avoid overeating when served larger portions). Finally, a tendency to 
endorse compensatory health beliefs – the belief that energy in the form of calories can be 
compensated for by restricting or increasing energy intake or expenditure over the course of the day 
– may be associated with the likelihood of compensating for low calorie meals [46]. To our 
knowledge no study has investigated compensatory health beliefs as a potential moderator of the 
PSE. 
From a public health perspective, investigating how people of lower SEP respond when exposed to 
smaller vs. larger portions of foods is of interest because there is a need for equitable interventions 
that influence dietary behaviour in a way that reduces health inequalities [22], [23]. If people of 
lower SEP are more prone to being influenced by the external or ‘structural’ aspects of their food 
environment [15], [24] then reducing portion sizes of commercially provided food may be of 
particular benefit to lower SEP populations and therefore narrow SEP-based inequalities in diet. 
 
 

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2. OBJECTIVES, OUTCOMES MEASURES AND HYPOTHESES 
OBJECTIVES 
OUTCOME MEASURES 
HYPOTHESES 
Primary objective 
To examine the impact of 
portion size on energy intake 
among participants of lower 
vs. higher SEP. 
 
 
Energy intake (kcal) 
Total energy consumption will 
be higher from larger 
compared to smaller portions 
(PSE). 
 
The PSE will be larger in 
participants of lower vs. higher 
SEP. 
Secondary objectives 
 
To examine the reasons why 
the PSE may vary based on 
participants’ SEP. 
 
If no relationship exists, we 
will examine whether the 
individual difference measures 
moderate the PSE 
 
 
Impulsivity 
Inhibition 
Portion size appropriateness 
Satiety responsiveness 
Plate clearing tendencies 
Perceived food insecurity 
Resource availability in 
childhood 
Food choice motives 
Compensatory health beliefs 
 
 
The relationship between SEP 
and PSE may be mediated by 
individual difference 
measures. 
 
 
 
3. EXPERIMENTAL DESIGN 
Participants will be randomised into a cross-over design with two study days corresponding to two 
conditions: larger portion size condition or smaller portion size condition. Each study day will last 
one day and be separated by a minimum 1-week and maximum 6-week washout period. The two 
study days will be scheduled for the same day each week. On both days, participants will be served 
all meals ad libitum in the lab (including breakfast and second helpings) and will be provided with 
snacks to consume outside of the lab – but only the size of the initial portion of the main meal 
provided for lunch and dinner will be manipulated. Energy intake from all meals and snacks will be 
recorded. 
4. PARTICIPANTS AND RECRUITMENT 
 
4.1. Recruitment 
Recruitment advertisements will be placed on social media (Facebook, Instagram, Twitter), online 
noticeboards (Gumtree, Call for Participants), and University of Liverpool (and other local 
universities’) staff and students announcements and mailing lists. Flyers and posters will be 
distributed around the University of Liverpool campus, and if needed in local businesses and via 
letterbox drops in local residences with a particular focus on the most deprived areas based on the 
Index of Multiple Deprivation (IMD). Participants will be reimbursed for their time and expenses (£70 
at the end of the study).  
Recruitment will be stratified by highest educational qualification achieved or currently studying for 
as follows: 
- 
50% lower qualification levels 

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o No formal qualifications 
o 1–3 GCSEs or equivalent 
(Level 1: first certificate; GCSE – grades 3, 2, 1 or grades D, E, F, G; level 1 award; level 1 certificate; level 
1 diploma; level 1 ESOL; level 1 essential skills; level 1 functional skills; level 1 national vocational 
qualification (NVQ); music grades 1, 2 and 3) 
o 4+ GCSEs or equivalent 
(Level 2: CSE – grade 1; GCSE – grades 9, 8, 7, 6, 5, 4 or grades A*, A, B, C; intermediate apprenticeship; 
level 2 award; level 2 certificate; level 2 diploma; level 2 ESOL; level 2 essential skills; level 2 functional 
skills; level 2 national certificate; level 2 national diploma, level 2 NVQ; music grades 4 and 5; O level – 
grade A, B or C) 
o A level or equivalent 
(Level 3: A level; access to higher education diploma; advanced apprenticeship; applied general; AS 
level; international Baccalaureate diploma; level 3 award; level 3 certificate; level 3 diploma; level 3 
ESOL; level 3 national certificate; level 3 national diploma; level 3 NVQ; music grades 6, 7 and 8; tech 
level) 
- 
50% higher qualification levels 
o Certificate of higher education (CertHE) or equivalent 
(Level 4: certificate of higher education (CertHE); higher apprenticeship; higher national certificate 
(HNC); level 4 award; level 4 certificate; level 4 diploma; level 4 NVQ);  
o Diploma of higher education (DipHE) or equivalent 
(Level 5: diploma of higher education (DipHE); foundation degree; higher national diploma (HND); level 
5 award; level 5 certificate; level 5 diploma; level 5 NVQ) 
o Bachelor or equivalent 
(Level 6: degree apprenticeship; degree with honours – for example bachelor of the arts (BA) hons, 
bachelor of science (BSc) hons; graduate certificate; graduate diploma; level 6 award; level 6 certificate; 
level 6 diploma; level 6 NVQ; ordinary degree without honours) 
o Master’s degree or equivalent 
(Level 7: integrated master’s degree, for example master of engineering (Meng); level 7 award; level 7 
certificate; level 7 diploma; level 7 NVQ; master’s degree, for example master of arts (MA), master of 
science (MSc); postgraduate certificate; postgraduate certificate in education (PGCE); postgraduate 
diploma) 
o Doctorate or equivalent 
(Level 8: doctorate, for example doctor of philosophy (PhD or Dphil); level 8 award; level 8 certificate; 
level 8 diploma) 
We will also aim to stratify recruitment by age (50% 18-25 years; 50% 26+ years), with equal 
proportions of each age group in each education group (lower, higher). 
4.2. Inclusion criteria 
 
• 
Female only 
• 
UK residents, age ≥ 18 
• 
BMI between 22.5 and 32.5 kg/m2; as approximately 70% of adults in England have a BMI within 
this range [25] 
• 
Proficiency in English language 
• 
Self-report liking each of the test foods 
 
4.3. Exclusion criteria 
 
• 
Current medication use which affects appetite 
• 
Pregnancy (as it may affect appetite) 
• 
Current or historic diagnosed eating disorder 
• 
Currently on a diet 

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• 
Dietary restriction: 
o Vegetarian 
o Vegan 
o Gluten-free 
o Sugar-free 
o Dairy/lactose-free 
o Food allergy (e.g. milk, eggs, nut, wheat, fish, etc.) 
 
 
5. METHODS 
 
5.1. Test meals 
The portion-manipulated test meals will consist of a pasta-based dish for lunch (3 cheese pasta), and 
a dish served with rice for dinner (chilli con carne), see Table 1 for more information about the 
dishes. The portion sizes are informed by pilot studies, including pilot studies conducted to assess 
the norm range, with portions in the larger portion size condition from the mid-higher end of the 
range, and portion sizes in the smaller portion size condition from the lower end of the norm range 
(see Appendix A). 
Table 1. Portion sizes for each portion-manipulated dish in g and kcal 
 
Larger portion size 
(100%) 
Smaller portion size 
(67%) 
 
g 
kcal 
£ 
g 
kcal 
£ 
Lunch  
3 cheese pasta 
563 
816 
2.46 
375 
544 
1.64 
Dinner  
Chili con carne & rice 
 
437 
509 
 
0.90 
 
291 
 
339 
0.60 
Dinner including cheese 
and vegetables on the 
side (totals) 
557 
737 
1.24 
411 
568 
0.94 
 
On each study day, all participants will receive the same ad libitum breakfast in the lab (initial 
serving providing 1437 kcal) and the same snack box for consumption away from the lab throughout 
the day (providing 906 kcal). At lunch, participants will have the opportunity to serve themselves 
more of the main dish. At dinner, participants will be served their main dish with a side of vegetables 
and they will also have the opportunity to request seconds of the main dish. After their dinner a 
dessert buffet with three options will be provided (providing 1528 kcal). Chilled water (500mL) will 
be served with each in-lab meal. The complete study menu can be found in SEP_portion_size 
MENU_UPDATED_TL.xlsx. 
Participants will be requested 1/ not to consume any additional food apart from the items provided 
as part of the study, and 2/ drink only tea, coffee, and no calorie drinks (water) as they usually 
would. 
Note for each self-service breakfast meal we will also vary the size of the dishware (smaller vs 
larger), the results of which will be reported in detail elsewhere. Given evidence to date (e.g. 
[47,48]), we expect this to have no impact on energy intake at breakfast, and this will be tested in 
analyses (see analysis plan). Manipulation of dishware size (smaller followed by larger dishware size 

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vs larger followed by smaller dishware size) will be fully counterbalanced with the order of portion 
size presentation (smaller followed by larger portions vs larger followed by smaller portions). 
 
5.2. Measures 
 
5.2.1. Energy intake during test meals (breakfast, lunch, dinner and dessert) 
All the foods served in the lab will be weighed before and after breakfast/lunch/dinner/dessert in 
order to determine how much of each food has been consumed by the participants. Energy intake 
will be calculated by multiplying the consumed weight of each food by the energy density (kcal/g) 
provided by the food manufacturer. 
5.2.2. Energy intake from the snack box 
Participants will be asked to take a photo of their snack box before bed and send it to the research 
team via email or WhatsApp. They will be told that all items must be photographed (e.g. if they have 
eaten a chocolate bar, the empty wrapper must be photographed). Participants will be asked to 
return the snack box including all food and wrappers the following day during the washout session. 
Returned items will be checked against the photo in case any items are missing on return, which can 
then be clarified with the participant. Energy intake from the snack box will be calculated by 
multiplying the consumed weight of each food by the energy density (kcal/g) provided by the food 
manufacturer.  
5.2.3. Additional energy intake 
Participants will be asked not to eat any food apart from the meals and snacks provided during each 
testing period. To assess compliance and to more accurately measure total energy intake, 
participants will be asked to provide details of any extra food and drink (excluding water) they 
consumed outside of the study, during the washout and final sessions. Participants will be reassured 
that they will not be penalised for eating additional food, only that we need to keep detailed records 
of it. To calculate additional energy intake, a researcher will enter the recorded additional food 
items into intake24, an online dietary assessment tool [26], [27]. 
5.2.4. Hunger and fullness 
Participants will rate their current level of hunger and fullness on visual analog scales ranging from 0 
to 100 before and after eating each meal in the lab. 
5.2.5. Physical activity 
Participants will be asked not to perform any vigorous physical activity during the study days and to 
keep their level of physical activity identical across all the testing days. To encourage compliance 
with the protocol and to control for potential variation in physical activity level, participants will 
wear an activity monitor (Fitbit Zip) continuously during each study day (except while bathing) to 
assess moderate-vigorous physical activity. Fitbit device estimates of active minutes have been 
validated against gold standard research-grade physical activity monitoring devices, and Fitbit 
devices have been demonstrated to have high reliability. 
5.2.6. Impulsivity 
We will use the 30-item Barratt Impulsiveness Scale to measure self-reported trait impulsivity [28] 
(APPENDIX B). 

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5.2.7. Inhibition 
A Stroop task will be used to measure inhibition (≈2min.30sec.). In this task, participants are given 
colour words (e.g. “red”) written in colour and are asked to indicate the colour of the word (not its 
meaning) by key press as fast as they can without making too many errors. Congruent trials: colour 
word and the colour it is presented in are the same. Incongruent trials: colour word and the colour it 
is presented in are not the same. Control trials: coloured rectangles. The task includes 4 colours (red, 
green, blue, black) x 3 colour-stimuli congruency (congruent, incongruent, control) x 7 repetitions = 
84 trials randomly sampled. 
5.2.8. Portion size appropriateness 
Participants will complete a computerised task in which they will be asked to select the portion size 
they consider appropriate to consume for the test foods (portion-manipulated main dishes: lunch 
and dinner). Food pictures start at 40 kcal and increase in 40 kcal increments up to 1000 kcal. 
5.2.9. Satiety responsiveness 
We will use the satiety responsiveness subscale of the Adult Eating Behaviour Questionnaire (AEBQ) 
[29] (APPENDIX C). 
5.2.10. Plate clearing tendencies 
We will use the 5-item plate clearing tendencies measure developed by Robinson and colleagues 
[49] Participants rate questions (e.g. “I always tend to clear my plate when eating”) from 1 (Strongly 
disagree) to 5 (Strongly agree) (APPENDIX D). 
5.2.11. Perceived food insecurity 
Food insecurity is defined as “limited or uncertain ability to acquire nutritionally adequate and safe 
food in socially acceptable ways” [30], [31]. We will use USDA 12-month Food Security Scale 
Questionnaire, one of the most widely use self-report questionnaires to measure food insecurity 
[19]. Given the high volume of questionnaire measures in this study, we opt to use the 6-item short-
form version as this has been found to have reasonable sensitivity and specificity as compared to the 
full 18-item [32] with less burden to the participant (APPENDIX E). 
5.2.12. Resource availability in childhood 
Participants will complete a 3-item measure of perceived resource availability during childhood 
developed in 2011 by Griskevicius et al. [33] and used in previous studies investigating the 
relationship with obesity or eating behaviour [20], [21] (APPENDIX F). 
5.2.13. Food choice motives 
To assess food choice motives we will use the ‘Health’ (6 items, e.g. “Keeps me healthy”) and 
‘Weight control’ (3 items, e.g. “Is low in calories”) subscales from the Food Choice Questionnaire 
[50]. These questions are rated from 1 (Not at all important) to 4 (Very important) (APPENDIX G).s  
5.2.14. Compensatory health beliefs 
We will use two measures of compensatory health beliefs, forming a 7-item questionnaire (adapted 
from [51,52]). We will use the 3-item weight-regulation subscale developed by Knäuper and 
colleagues [51]. Participants rate from 1 (not at all) to 5 (very much) how much the compensatory 
health belief matches their own belief around weight regulation (e.g. “Eating dessert can be made 

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up for by skipping the main dish”). We will also use the 4-item portion size subscale developed by 
Poelman and colleagues [52]. Participants rate from 1 (not at all) to 5 (very much) how much the 
compensatory health belief matches their own belief around portion size (e.g. “If I eat a small meal, 
it’s fine to have a larger portion during the next meal”) (APPENDIX H).  
5.2.15. Other questionnaire measures 
We plan to collect some questionnaire items for the purpose of other research that will not be used 
in the present study (APPENDIX I). 
5.2.16. Demographic and socioeconomic status measures 
Participants will be ask to report their gender, age and ethnic group, employment status, and to 
report four measures of socioeconomic status: 
- 
their highest educational qualification; 
- 
their number of years in higher education; 
- 
their household income and their household composition; 
- 
a subjective measure of their socioeconomic status using the MacArthur Scale of Subjective 
Social Status (SSS) [34]. 
 
5.2.17. Study experience questionnaire 
Aims guessing. Participants will be asked to report what they thought the aims of the study were in 
an open-ended response format. 
Manipulation awareness. To assess awareness of the difference in portion sizes between the two 
study days, participants will be asked a series of questions with a yes/no response format about 
their experience of the study. The questions will consist of several filler questions to distract from 
the focus on portion size, and a single item to assess awareness of the portion size manipulation (“I 
noticed a difference in the size of the lunch and dinner portions between the two study days”). All 
the participants will also be asked to order the portion sizes (smallest and largest lunch and dinner 
portions) according to the study day (1 and 2) in which they were served. 
Food liking. Participants will be asked to report how much they liked (from 1 [not at all], to 7 [very 
much]), each of the specific foods presented in the study.  
Familiarity ratings. Participants will also be asked to indicate their agreement with the following 
statement, indicating familiarity with the foods served in the study: ‘’I would normally eat this type 
of food’ (rated from 1 [strongly disagree], to 7 [strongly agree]). 
Normality ratings. Participants will be shown a picture of each portion size of the portion-
manipulated lunch and dinner dishes and asked: “In your opinion, how normal is this portion? By 
‘normal’ we mean whether the portion contains a normal amount of food to eat for a single meal.” 
Responses will be collected on 7-point Likert scales ranging from 1 (not normal, it is far too small), to 
7 (not normal, it is far too big), with a midpoint of 4 (normal). 
5.2.18. Filler measures 
Participants will complete mood ratings before and after eating each meal (on visual analog scales 
ranging from 0 – 100 with embedded ‘hunger and fullness’ ratings) and computerised tasks assessing 
categorisation of positive versus neutral words during the lunch session each day as part of the 
cover story. Participants will also complete a daily sleep quality questionnaire to distract from the 
focus on food intake. 

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Computerised mood task. The computerised mood filler task consists of a 1-minute lexical decision 
task. The task will be introduced as “A new way to assess mood by measuring speed of responding to 
positive versus neutral words”. Five positive words, 5 neutral words, and 5 ‘non-words’ will be 
presented on the computer screen one by one in a random order. Participants will be asked to 
respond to each word/non-word by pressing the left or right key marked on the keyboard to indicate 
whether the task displays a word or non-word (according to the key assignment specified in the task 
instructions). There will be two different versions of the task, each consisting of different word sets – 
one for each study day. 
 
6. STUDY PROCEDURE 
To disguise the true purpose of the study, participants will be told that the study aims to investigate 
daily fluctuations in mood after accounting for lifestyle factors such as diet and sleep. To bolster the 
cover story, participants will complete mood ratings before and after eating each meal and 
computerised tasks assessing categorisation of positive versus neutral words at lunchtime during 
each study day. Participants will also complete a sleep quality questionnaire on each study day to 
distract from the focus on food intake. Data from mood and sleep measures will not be analysed.  
Figure 1 presents the sequence of steps in the study that are described Table 2. Occasionally, 
exceptions to the general rule will be made in order to fit within a participant’s schedule. 
 
Figure 1. Participants’ schedule 
Table 2. Description of the study procedure 
RECRUITMENT 
 
Participants respond to recruitment materials via email/phone 
 
Information sheet sent over email with link to online pre-
screening questionnaire (Qualtrics) 
 
Eligible participants are invited to a screening session in person 
to formally check that they meet the eligibility criteria 
1-6 weeks
Washout 
session
1-day experimental 
session 1
Mon/Tue/Wed/Thur/Fri
1-day experimental 
session 2
Mon/Tue/Wed/Thur/Fri
Final session
Screening 
session
Pre-screening 
online 
questionnaire
Response to 
recruitment 
materials
Informed consent
Randomisation

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SCREENING SESSION 
Informed consent 
o Ensure participants have read information sheet and 
explain the study in more details 
o Measure height and weight 
o Confirm eligibility 
o Participants sign the consent form and keep a copy 
o Organise the study with the participants: 
o Record contact information and preferred 
communication (text, call or email) 
o Organise individual schedule 
o Explain FitBit use and physical activity restriction 
o Discuss allowed food / drink  
o Participants complete the baseline questionnaire: 
o Demographic questions 
o Portion size appropriateness 
o Stroop task 
 
RANDOMISATION 
 
Participants will be randomly assigned to receive the larger 
portion sizes at the first experimental session and the smaller 
portion sizes at the second experimental session or vice versa. 
 
A randomisation sequence will be created using Random 
Allocation Software [35] with a 1:1 allocation stratified by 
highest educational qualification (Group 1: low ≤ A level, 18-25 
years; Group 2: low ≤ A level, 26+ years, Group 3: ≥ degree, 18-
25 years, Group 4: ≥ degree, 26+ years). 
 
The allocations will be placed inside envelopes for each group; 
the envelopes will be sequentially opened each time a 
participant from one group consent to take part in the study. 
 
Participants’ two experimental sessions should take place on the 
same day of the week 
STUDY DAY 1 
 
 
Remind allowed food / drink, physical activity restriction and 
install the FitBit 
 
Sleep, mood, and hunger ratings 
 
Breakfast 30 minute session between 7 am and 10:30 am 
 
Snack box 
o Provide the snack box after breakfast 
 
Lunch 30 minute session (between 12pm and 2pm) 
 
Dinner 30 minute session (between 5pm and 7pm – at least 4 
hours after lunch) 
 
Organise the following steps: 
o Remind the date of the next session (washout) 
WASHOUT SESSION 
 
Participants return FitBit device and snack box 
 
Check if any additional foods/drinks consumed 
 
Remind participants about date of next session (Study Day 2) 

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STUDY DAY 2 
 
 
Remind allowed food / drink, physical activity restriction and 
install the FitBit 
 
Sleep, mood, and hunger ratings 
 
Breakfast 30 minute session between 7 am and 10:30 am 
 
Snack box 
o Provide the snack box after breakfast 
 
Lunch 30 minute session (between 12pm and 2pm) 
 
Dinner 30 minute session (between 5pm and 7pm – at least 4 
hours after lunch) 
 
Organise the following steps: 
o Remind the date of the next session (final session) 
FINAL SESSION 
 
 
Participants return FitBit device and snack box 
 
Check if any additional foods/drinks consumed 
 
Battery of measures 
o Barratt Impulsiveness Scale 
o Satiety responsiveness 
o Plate clearing tendencies  
o Perceived food insecurity 
o Resource availability in childhood 
o Food choice motives 
o Compensatory health beliefs 
 
Study experience questionnaire 
 
Debriefing: explain the purpose of the study, the cover story and 
provide opportunity to ask questions 
 
Financial compensation (£70) 
 
7. STATISTICAL ANALYSIS 
All statistical analyses will be performed using SPSS (Version 26.0). The level of significance will be 
set at p < 0.05 for primary analyses and p < 0.01 for secondary analyses to account for multiple 
testing.  
7.1. Participant’s characteristics 
A table will present the baseline characteristics. The table will include gender, age, ethnic group, 
employment status, highest educational qualification, years in higher education, household income, 
subjective socioeconomic status and BMI for all the participants and for lower and higher education 
groups. Continuous variables will be summarised using means and standard deviations. Categorical 
variables will be summarised using counts and percentages. We will test for baseline differences 
between SEP groups (higher vs lower) on demographic variables using t-tests (or if data does not 
meet parametric assumptions – i.e. not normally distributed – Wilcoxon Mann-Whitney tests will be 
used) and chi-square tests.  
7.2. Variables description 
 
7.2.1. Primary outcome 
Daily energy intake i.e., energy (kcal) from breakfast, lunch and dinner (main and dessert) in the lab, 
from the snack box and any self-reported additional foods consumed, summed to provide daily 
energy intake. 
Secondary outcomes  

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Hunger and fullness. Each participant will have 12 measures of hunger and fullness: [breakfast, 
lunch, dinner] x [pre meal, post meal] x [larger portion size, smaller portion size]. Daily hunger and 
fullness ratings across time will be summarised by calculating the area under the curve (AUC) using 
the trapezoid function [36]. 
Physical activity will be operationalised as ‘active minutes’ per day which are logged for activities 
with a metabolic equivalent (MET) of ≥3. 
7.2.2. Independent variables 
Socioeconomic position (SEP)  will be derived from highest educational qualification, coded as lower 
(1 = No formal qualifications; 2 = 1–3 GCSEs; 3 = 4+ GCSEs; 4 = A level) or higher (5 = Certificate of 
higher education (CertHE); 6 = Diploma of higher education (DipHE); 7 = Bachelor; 8 = Master’s 
degree; 9 = Doctorate). 
Impulsivity. Items from the Barratt Impulsiveness Scale will be coded from 1 to 4. The higher the 
summed score for all items, the higher the level of impulsiveness (min. = 30, max. = 120).  
McDonald’s Omega will be calculated as an indicator of internal consistency. 
Inhibition. For correct responses, the median reaction times (RTs) in incongruent and congruent 
trials will be calculated [53,54]. The difference in median RTs between incongruent vs congruent 
trials will be calculated [incongruent RT – congruent RT] = The Stroop interference effect. Higher 
scores indicate poorer response inhibition. 
Portion size appropriateness. For each participant the average selected portion size will be 
calculated in kcal. 
Satiety responsiveness. Items will be coded from 1: strongly disagree, to 5: strongly agree and their 
mean will be calculated. A higher score indicates a higher satiety responsiveness. McDonald’s 
Omega will be calculated as an indicator of internal consistency. 
Plate clearing tendencies. Response options range from 1 to 5: 1 = strongly disagree, to 5 = strongly 
agree. Responses will be averaged. Higher scores indicate higher plate clearing tendencies. 
McDonald’s Omega will be calculated as an indicator of internal consistency. 
Perceived food insecurity. Based on the recommendations of the authors of the questionnaire [55] 
responses to the 6 questions about food insecurity will be coded as affirmatives (i.e. “yes”, “often 
true”, “sometimes true”, “almost every month”, “some months but not every month”) and negatives 
(i.e. “no”, “never true”, “only 1 or 2 months”). Coding of food security is based on the number of 
affirmatives as follows: 0-1 =“food secure”, 2-4 = “food insecure without hunger”, 5-6 = “food 
insecure with hunger”. The responses “don’t know” and blank responses reflect missing data, which 
will be imputed following best practice guidance [55].   
Resource availability in childhood. Each item will be coded from 1 = strongly disagree, to 7 = 
strongly agree and an index of resource availability in childhood will be calculated as the mean of the 
three items. McDonald’s Omega will be calculated as an indicator of internal consistency. 
Food choice motives. Both health and weight control scores will be computed by averaging ratings 
for individual items of each dimension (health motivation: 6 items; weight control motivation: 3 
items). Response options range from 1 to 4: 1 = Not at all important; 2 = A little important; 3 = 
Moderately important; 4 = Very important. Higher scores indicate stronger motives around health 
and weight control respectively. McDonald’s Omega will be calculated as an indicator of internal 
consistency for both scores.  

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SEP and portion size effect protocol 
Compensatory health beliefs. Response options range from 1 to 5: 1 = not at all, 2 = a little, 3 = 
somewhat , 4 = quite a bit, 5 = very much. Higher scores indicate stronger compensatory health 
beliefs. McDonald’s Omega will be calculated as an indicator of internal consistency and if this is 
consistent across the two measures (weight regulation and portion size) scores will be averaged. 
7.2.3. Other variables 
BMI. Calculated as weight (kg) / Height (m2) 
Aim guessing. Participants who identify the aim of the study as being to examine the influence of 
portion/meal size on food intake/appetite will be coded as being aware of the study aims. Responses 
will be independently coded by two researchers, with discrepancies in coding decisions resolved by a 
third researcher. 
Manipulation awareness. Two binary variables: self-reported awareness (0: unaware, 1: aware) and 
observed awareness (0: wrong answer to ordering task, 1: right answer to the ordering task). 
Liking, familiarity, and normality ratings. Scores range: 1 to 7. 
7.3. Missing data 
We do not anticipate missing data on energy intake due to participant non-attendance (if a 
participant misses a meal and it is not possible to reschedule for a later time that day, they will be 
required to begin that study day again). Every effort will be made to keep the number of missing 
data due to researchers’ error to the lowest. The extent of the missing data will be reported. We 
plan to analyse complete cases only. 
Missing data on other variables will not be allowed by the experimental procedure because the 
record for each participant will be checked after each study day and the participants will be asked to 
provide their answers again if case of any missing data. 
 
7.4. Primary analyses 
 
7.4.1. Confirmatory analyses 
To be consistent with previous studies we ran investigating the effect of SEP on intended energy 
consumption (e.g [45]), the primary measure of SEP used in our primary analysis will be will be 
highest educational qualification (binary – lower vs higher). 
A mixed ANOVA will be used to test the effect of portion size (categorical: larger, smaller; within-
subject), SEP (categorical: lower (≤ A level), higher (> A level), between-subjects), the interaction 
portion size*SEP on daily energy intake.  If the interaction between portion size*SEP is significant the 
analysis will be stratified by SEP (≤ A level, > A level) and two repeated-measures t-tests will be used 
to examine the effect of portion size (larger vs smaller) on daily energy intake in the two groups of 
participants separately. We will not correct for multiple comparisons as we specified a priori 
hypotheses. 
7.4.2. Sensitivity analyses 
Sensitivity analyses will be conducted to examine whether the pattern of results from the main 
analyses differ after 1/ excluding participants guessing the aims of the study, 2/ excluding outliers on 
main outcome variables (identified as those with a value > 3SD from condition mean) and influential 
cases (identified as those with a Cook’s distance > 1, indicating a multivariate outlier [37], 3/ 

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SEP and portion size effect protocol 
substituting SEP measure (highest educational qualification, ≤ A level, > A level) with alternative 
measures of SEP (level of education – composite score, subjective socioeconomic status (1-10), and 
household income).  
The main analyses will also be repeated controlling for any non-SEP based demographic variables 
(e.g. BMI, age) that significantly differ between the higher vs. lower SEP groups in order to examine 
if results remain consistent. To examine whether the order that portions are presented impacts the 
findings, the main analyses will be repeated with an additional 2-level between-subjects factor 
(portion size order: smaller, larger vs larger, smaller). Finally, the main analyses will be repeated with 
dishware size as an additional 2-level within-subjects factor (dishware size: smaller vs larger). 
We will report whether sensitivity analyses result in deviations from the pattern of significance to 
the main analyses (i.e., any significant differences between conditions becoming not significant, and 
vice versa). 
Note if >30% participants guess the study aim we will include aim guessing as a between-subjects 
factor in ANOVA rather than use listwise removal. 
 
 
7.5. Secondary analyses 
 
7.5.1. Mediation analyses 
For each participant, we will compute the average daily energy intake in the larger portion condition 
minus average daily energy intake in the smaller portion size condition, referred below as the 
portion size effect (PSE).  
We will first report and compare the individual measures of impulsivity, inhibition, portion size 
appropriateness, satiety responsiveness, plate clearing tendencies, perceived food insecurity, 
resource availability in childhood, food choice motives, and compensatory health beliefs for lower 
and higher SEP groups using means, standard deviations and T-tests. If we find individual differences 
for any of these measures between participants of lower and higher SEP, mediation analyses will be 
performed in order to examine the extent to which it mediates the effect of SEP on the PSE (Figure 
2). 
 
 
 
 
 
 
Figure 2. Mediation diagrams for the PSE. Indirect effect of SEP on the PSE through a mediator M = 
c-c’ = ab. 
 
SEP 
c 
PSE 
SEP 
PSE 
c' 
M 
a 
b 

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SEP and portion size effect protocol 
The mediation will be tested by estimating the indirect effects of SEP on the PSE through all the 
potential mediators and testing their indirect effect using bias-corrected bootstrap. We will use the 
PROCESS macro (Model 4 – one mediator at a time and all together) in SPSS that provides 
asymmetric bias-corrected bootstrap confidence intervals for inference about the indirect effects 
using 5,000 bootstrap samples [38]. Mediation will be tested by determining whether or not the 
confidence intervals of the indirect effects estimates contain zero. 
If we do not find evidence that the PSE is moderated by SEP or that our individual difference 
measures do not explain moderation by SEP, we will repeat the primary analysis replacing SEP with 
the individual measures, to examine whether any of the individual difference measures moderates 
the main effect of portion size on daily energy intake.  
 
7.5.2. Hunger and fullness 
To investigate whether portion size reduction is associated with increased hunger/decreased 
fullness repeated-measures t-tests will be used to test the effect of portion size (categorical: larger, 
smaller; within-subject), on AUC for hunger and fullness. 
7.5.3. Physical activity 
To check whether the participants followed the instructions properly, we will investigate whether 
portion size reduction is associated with compensatory reductions in physical activity. A repeated-
measures t-test will be used to test the effect of portion size (categorical: larger, smaller; within-
subject) on the number of active minutes per day.  
7.5.4. Study experience 
We will report liking, familiarity, and normality ratings for each portion-size manipulated dish. We 
will also report the number of participants (total and in each group) who declared being aware of 
the portion-size manipulation and compare their observed awareness to chance expectation and to 
observed awareness of participants who declared not to be aware of the portion size manipulation 
(Chi-square test). 
 
7.6. Sample size 
In a previous study that used the same basic methodology but investigated the PSE over a 5-day 
period [39], the main effect of portion size on daily energy intake was partial η2 = 0.41 – considered 
a statistically large effect size. From other studies examining shorter time frames, the effect of 
portion size on energy intake is medium-sized [7, 57]. To be conservative we will power the present 
study to be able to detect a small to medium size main effect of portion size on daily energy intake 
(f=0.175, p < .05, 85% power, within-subject correlation of 0.7 conservatively estimated from [39]), 
resulting in a minimum sample size of 46 participants. As there is limited evidence on the size of 
moderating effect of SEP on portion size, this sample size also provides adequate power to detect 
the same small to medium sized portion size and SEP interaction (within-between-subject 
interaction) on energy intake. Due to on-going COVID restrictions there is uncertainty over 
recruitment rates and it may be plausible to recruit more participants into the study. If it is feasible 
in the time frame of the project, we will aim to recruit up to a further 14 participants, resulting in a 
final N=60. This decision will be made prior to conducting any data analyses. Increasing sample size 
by approximately 30% would address uncertainty for power analysis parameters (e.g. a smaller than 

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SEP and portion size effect protocol 
anticipated sized effect being observed in the study) by increasing power. Furthermore, empirical 
estimates of sample sizes needed for reasonable power (e.g. 80%) in mediation analyses indicate 
that a sample of ≈ 60 would be sufficient to detect mediation through pathways that are medium 
and above in statistical size using bias-corrected bootstrap tests [40].  
 
 
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9. Appendices 
9.1. APPENDIX A: SUMMARY OF PILOT STUDIES  
Based on two previous pilot studies, we selected foods that are palatable for the study population 
and portion sizes that are perceived as ‘normal’ in order to limit potential compensatory eating after 
consuming a meal perceived as being ‘smaller than normal’. 
In a first pilot study, a selection of seven candidate main meal dishes (3 pasta lunchtime dishes: 
penne with pesto, spaghetti carbonara, spaghetti Bolognese; 4 dinner dishes: beef curry, chicken 
korma curry, chilli con carne, sweet and sour chicken [all served with rice]) were photographed on 
standard-sized (28.5cm diameter) dinner plates at portion sizes ranging from 40 to 300% of a 
reference portion (equal to the manufacturer’s recommended serving for commercially available 
foods, or equivalent to similar commercially available foods for recipes prepared from ingredients). 
Participants (N = 30, 50% female) completed a computer-based rating task in which they viewed 
each portion size in a randomised order, and indicated whether they perceived that portion as a 
‘normal’ or ‘not normal’ amount to eat. The proportion of the sample that perceived each portion 
size as ‘normal’ in size to determine the ‘norm range’ for each dish (i.e., the range of portions 
perceived as ‘normal’ by at least 60% of the sample) was calculated. The reduced portion size for 
each food was selected from the lower end of the norm range, the large portion size from the mid-
high end of the norm range. 
In a second pilot study, 10 participants (50% female) viewed each main meal dish in the two portion 
sizes in person. Participants rated the perceived normality of each portion for each dish (grouped by 
dish, such that they rated the normality of each portion for the first dish, followed by each portion 
size for the second dish, and so on) on a Likert scale ranging from 1 (“not normal – too small”) to 7 
(“not normal – too large”), with a midpoint of 4 (“normal”). Participants subsequently tasted each 
dish and rated how much they liked the taste on a 7-point Likert scale ranging from 1 (“dislike very 
much”) to 7 (“like very much”). All dishes were at least moderately liked by all participants, such that 
only a small number of participants rated their liking of the meals below the midpoint of the scale (n 
= 0 participants for chilli, n = 2 participants for Bolognese, carbonara, pesto, beef curry), and the 
mean liking rating was above the midpoint of the scale for all dishes (mean ratings for each rice 
dishes was significantly larger than 4, while the mean ratings for each pasta dish was at least 4.5, but 
did not significantly differ from 4). For most dishes, the mean ratings of the reduced portion sizes did 
not significantly differ from the midpoint of the scale, and the majority (at least 60%) of participants 
provided a normality rating of ‘4’ for most dishes indicating that participants perceived these 
portions as ‘normal’. There were two exceptions: the mean normality rating for the reduced portion 
of pasta with pesto was significantly higher than 4 (indicating perceived ‘larger than normal’), and 
the mean normality rating for the reduced portion of chicken with sweet and sour sauce was 
significantly lower than 4 (indicating perceived ‘smaller than normal’). To ensure that the portions 
were perceived as at least normal in size, sweet and sour chicken with rice was omitted from the 
menu.  
Finally, given logistical considerations (in part relating to running experiments during COVID-19), we 
decided that each experimental session would last 1 day, meaning only one lunch option and one 
dinner option would be required. We decided on a final menu based on these pilot studies and 
logistical considerations, giving 1 lunchtime pasta dish (3-cheese pasta) and 1 dinner dish (chili-con-
carne with rice). 
 
 

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9.2. APPENDIX B: BARRATT IMPULSIVENESS SCALE 
Instruction: “Read each statement and select the appropriate response. Do not spend too much 
time on any statement. Answer quickly and honestly.” 
 
 
Rarely/Never 
 
1 
Occasionally 
 
2 
Often 
 
3 
Almost 
always/Always 
4 
1. 
I “squirm” at plays or lectures. 
o 
 
o 
 
o 
 
o 
 
2. 
I am restless at the theatre or lectures. 
o 
 
o 
 
o 
 
o 
 
3. 
I don’t “pay attention.” 
o 
 
o 
 
o 
 
o 
 
4. 
I concentrate easily.* 
o 
 
o 
 
o 
 
o 
 
5. 
I am a steady thinker.* 
o 
 
o 
 
o 
 
o 
 
6. 
I act “on impulse.” 
o 
 
o 
 
o 
 
o 
 
7. 
I act on the spur of the moment. 
o 
 
o 
 
o 
 
o 
 
8. 
I buy things on impulse. 
o 
 
o 
 
o 
 
o 
 
9. 
I make-up my mind quickly. 
o 
 
o 
 
o 
 
o 
 
10. 
I do things without thinking. 
o 
 
o 
 
o 
 
o 
 
11. 
I spend or charge more than I earn. 
o 
 
o 
 
o 
 
o 
 
12. 
I am happy-go-lucky. 
o 
 
o 
 
o 
 
o 
 
13. 
I am a careful thinker.* 
o 
 
o 
 
o 
 
o 
 
14. 
I plan tasks carefully.* 
o 
 
o 
 
o 
 
o 
 
15. 
I am self-controlled.* 
o 
 
o 
 
o 
 
o 
 
16. 
I plan trips well ahead of time.* 
o 
 
o 
 
o 
 
o 
 
17. 
I plan for job security.* 
o 
 
o 
 
o 
 
o 
 
18. 
I say things without thinking. 
o 
 
o 
 
o 
 
o 
 
19. 
I like to think about complex problems.* 
o 
 
o 
 
o 
 
o 
 
20. 
I like puzzles.* 
o 
 
o 
 
o 
 
o 
 
21. 
I save regularly.* 
o 
 
o 
 
o 
 
o 
 
22. 
I am more interested in the present than the 
future. 
o 
 
o 
 
o 
 
o 
 
23. 
I get easily bored when solving thought 
problems. 
o 
 
o 
 
o 
 
o 
 
24. 
I change residences. 
o 
 
o 
 
o 
 
o 
 
25. 
I change jobs. 
o 
 
o 
 
o 
 
o 
 
26. 
I am future oriented.* 
o 
 
o 
 
o 
 
o 
 
27. 
I can only think about one problem at a time. 
o 
 
o 
 
o 
 
o 
 
28. 
I often have extraneous thoughts when 
thinking. 
o 
 
o 
 
o 
 
o 
 
29. 
I have “racing” thoughts. 
o 
 
o 
 
o 
 
o 
 
30. 
I change hobbies. 
o 
 
o 
 
o 
 
o 
 
*reverse scoring 
 
 

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SEP and portion size effect protocol 
9.3. APPENDIX C: SATIETY RESPONSIVENESS 
 
 
 
 
 
Strongly 
disagree 
1 
Disagree 
 
2 
Neither agree 
nor disagree 
3 
Agree 
 
4 
Strongly 
agree 
5 
1. 
I often leave food on my plate at the 
end of a meal. 
o 
 
o 
 
o 
 
o 
 
o 
 
2. 
I often get full before my meal is 
finished. 
o 
 
o 
 
o 
 
o 
 
o 
 
3. 
I get full up easily. 
o 
 
o 
 
o 
 
o 
 
o 
 
4. 
I cannot eat a meal if I have had a 
snack just before. 
o 
 
o 
 
o 
 
o 
 
o 
 

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SEP and portion size effect protocol 
9.4. APPENDIX D: PLATE CLEARING TENDENCIES 
 
 
 
Strongly 
disagree 
1 
Disagree 
 
2 
Neither agree 
nor disagree 
3 
Agree 
 
4 
Strongly 
agree 
5 
1. 
I always tend to clear my plate when 
eating. 
o 
 
o 
 
o 
 
o 
 
o 
 
2. 
I normally finish eating when my 
plate is empty. 
o 
 
o 
 
o 
 
o 
 
o 
 
3. 
Before I start eating, I normally plan 
to finish the serving I am about to 
eat  
o 
 
o 
 
o 
 
o 
 
o 
 
4. 
I rarely leave food on my plate  
o 
 
o 
 
o 
 
o 
 
o 
 
5. 
It is normal for me to have very little 
food left or an empty plate at the 
end of a meal 
o 
 
o 
 
o 
 
o 
 
o 
 
  
 
 

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SEP and portion size effect protocol 
9.5. APPENDIX E: PERCEIVED FOOD INSECURITY 
Instructions: These next questions are about the food eaten in your household in the last 12 months 
and whether you were able to afford the food you need.  
Here are two statements that people have made about their food situation. Please tell me whether 
the statement was OFTEN, SOMETIMES, or NEVER true for (you/you and the other members of your 
household) in the last 12 months. 
 
 
 
 
NOTES.  
If any of the first 3 questions are answered affirmatively (i.e., if either Q3 or Q4 are "often true [1]" 
or "sometimes true [2]" or Q8 is "yes" [1]), the participant will proceed to Q8a. Otherwise, they will 
skip to Q9. 
All questions are optional (meaning there can be missing data). 
 
 
 
Often true 
1 
Sometimes true 
2 
Never true 
3 
Don’t know 
DK 
Q3 
The food that (I/we) 
bought just didn't last, 
and (I/we) didn't have 
money to get more 
 
 
 
 
Q4 
(I/we) couldn't afford 
to eat balanced meals 
 
 
 
 
 
 
Yes 
1 
No 
2 
Don’t know 
DK 
Q8 
In the last 12 months, since (date 12 
months ago) did (you/you or other 
adults in your household) ever cut the 
size of your meals or skip meals because 
there wasn't enough money for food? 
o 
 
o 
 
o 
 
 
 
Almost every 
month 
1 
Some months but 
not every month 
2 
Only 1 or 2 
months 
3 
Don’t know 
 
DK 
Q8a 
How often did this 
happen? 
o 
 
o 
 
o 
 
o 
 
 
 
Yes 
1 
No 
2 
Don’t know 
DK 
Q9 
In the last 12 months, did you 
ever eat less than you felt you 
should because there wasn't 
enough money to buy food? 
o 
 
o 
 
o 
 
Q10 
In the last 12 months, were you 
ever hungry but didn't eat 
because you couldn't afford 
enough food? 
o 
 
o 
 
o 
 

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9.6. APPENDIX F: PERCEIVED RESOURCE AVAILABILITY IN CHILDHOOD 
 
Instructions: Think about your childhood before age 12 and rate your agreement or disagreement 
with the following statements. 
 
Strongly 
disagree 
1 
 
 
 
 
 
Strongly 
agree 
7 
My family had enough money for things growing up. 
o 
 
 
 
 
 
 
o 
 
I grew up in a relatively wealthy neighbourhood. 
o 
 
 
 
 
 
 
o 
 
I felt relatively wealthy compared to others my age. 
o 
 
 
 
 
 
o 
 
 
 
 
 

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9.7. APPENDIX G: HEALTH AND WEIGHT CONTROL FOOD CHOICE MOTIVES 
Instruction: “Several different factors influence our choice of food. Read each item carefully and 
decide how important the item is to you. There are no right or wrong answers, we are interested in 
what is important to you.” 
It is important to me that the food I eat on a typical day… 
 
 
Not at all 
important 
1 
A little 
important 
2 
Moderately 
important 
3 
Very 
important 
4 
Health 
1. 
contains a lot of vitamins and 
minerals 
o 
 
o 
 
o 
 
o 
 
2. 
keeps me healthy 
o 
 
o 
 
o 
 
o 
 
3. 
is nutritious 
o 
 
o 
 
o 
 
o 
 
4. 
is high in protein 
o 
 
o 
 
o 
 
o 
 
5. 
is good for my 
skin/teeth/hair/nails etc. 
o 
 
o 
 
o 
 
o 
 
6. 
is high in fibre and roughage 
o 
 
o 
 
o 
 
o 
 
Weight control 
7. 
is low in calories 
o 
 
o 
 
o 
 
o 
 
8. 
helps me control my weight 
o 
 
o 
 
o 
 
o 
 
9. 
is low in fat 
o 
 
o 
 
o 
 
o 
 
10. 
This is an attention check. 
Please choose the answer (2) 
‘A little important’ 
o 
 
o 
 
o 
 
o 
 
 
 

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SEP and portion size effect protocol 
9.8. APPENDIX H: COMPENSATORY HEALTH BELIEFS 
Instruction: “Different people believe different things regarding their health. Below is a list of beliefs 
that everyone may hold to some degree. Please read each sentence carefully and rate how closely 
the idea matches your own belief. Since we all believe different things, there are no correct or 
incorrect choices. As well, most of these beliefs have not been scientifically tested. How closely does 
each of the following ideas match your own belief?’’ 
 
 
 
 
 
 
 
 
 
 
 
 
 
Not at all 
1 
A little 
2 
Somewhat 
3 
Quite a bit 
4 
Very much 
5 
Eating dessert can be made up for by skipping the 
main dish 
o 
 
o 
 
o 
 
o 
 
o 
 
Using artificial sweeteners compensates for extra 
calories 
o 
 
o 
 
o 
 
o 
 
o 
 
Breaking a diet today may be compensated for by 
starting a new diet tomorrow 
o 
 
o 
 
o 
 
o 
 
o 
 
If I eat a small meal, it’s fine to have a larger 
portion during the next meal 
o 
 
o 
 
o 
 
o 
 
o 
 
To maintain your weight, it is fine to eat a large 
meal, if you eat a small portion during the next 
meal 
o 
 
o 
 
o 
 
o 
 
o 
 
To maintain your weight, it is fine to eat a high 
caloric snack in between meals, if you compensate 
for this by eating a smaller portion later in the day 
o 
 
o 
 
o 
 
o 
 
o 
 
If I eat a small meal, there is no harm in eating 
more cookies and candies 
o 
 
o 
 
o 
 
o 
 
o 
 

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9.9. APPENDIX I: INTEROCEPTIVE ACCURACY SCALE 
 
Below are several statements regarding how accurately you can perceive specific bodily sensations. 
Please rate on the scale how well you believe you can perceive each specific signal. For example, if 
you often feel you need to urinate and then realise you do not need to when you go to the toilet you 
would rate your accuracy perceiving this bodily signal as low. 
Please only rate how well you can perceive these signals without using external cues, for example, if 
you can only perceive how fast your heart is beating when you measure it by taking your pulse this 
would not count as accurate internal perception. 
 
 
Strongly 
disagree 
 
1 
Disagree 
 
 
2 
Neither 
agree 
nor 
disagree 
3 
Agree 
 
 
4 
Strongly 
agree 
 
5 
1. I can always accurately perceive when my heart is beating fast 
o 
 
o 
 
o 
 
o 
o 
 
2. I can always accurately perceive when I am hungry 
o 
 
o 
 
o 
 
o 
o 
 
3. I can always accurately perceive when I am breathing fast 
o 
 
o 
 
o 
 
o 
o 
 
4. I can always accurately perceive when I am thirsty 
o 
 
o 
 
o 
 
o 
o 
 
5. I can always accurately perceive when I need to urinate 
o 
 
o 
 
o 
 
o 
o 
 
6. I can always accurately perceive when I need to defecate 
o 
 
o 
 
o 
 
o 
o 
 
7. I can always accurately perceive when I encounter different 
tastes 
o 
 
o 
 
o 
 
o 
o 
 
8. I can always accurately perceive when I am going to vomit 
o 
 
o 
 
o 
 
o 
o 
 
9. I can always accurately perceive when I am going to sneeze 
o 
 
o 
 
o 
 
o 
o 
 
10. I can always accurately perceive when I am going to cough 
o 
 
o 
 
o 
 
o 
o 
 
11. I can always accurately perceive when I am hot/cold 
o 
 
o 
 
o 
 
o 
o 
 
12. I can always accurately perceive when I am sexually aroused 
o 
 
o 
 
o 
 
o 
o 
 
13. I can always accurately perceive when I am going to pass 
wind 
o 
 
o 
 
o 
 
o 
o 
 
14. I can always accurately perceive when I am going to burp 
o 
 
o 
 
o 
 
o 
o 
 
15. I can always accurately perceive when my muscles are 
tired/sore 
o 
 
o 
 
o 
 
o 
o 
 
16. I can always accurately perceive when I am going to get a 
bruise 
o 
 
o 
 
o 
 
o 
o 
 
17. I can always accurately perceive when I am in pain 
o 
 
o 
 
o 
 
o 
o 
 
18. I can always accurately perceive when my blood sugar is low 
o 
 
o 
 
o 
 
o 
o 
 
19. I can always accurately perceive when someone is touching 
me affectionately rather than non-affectionately 
o 
 
o 
 
o 
 
o 
o 
 
20. I can always accurately perceive when something is going to 
be ticklish 
o 
 
o 
 
o 
 
o 
o 
 
21. I can always accurately perceive when something is going to 
be itchy 
o 
 
o 
 
o 
 
o 
o