Nutri-score Labelling in a UK Restaurant Setting: a Randomised Control Trial
Phase: NA
Conditions: PME, Food Choice, Food Labelling
Sponsor: University of Liverpool

 
 
 
Nutri-score labelling in a UK restaurant setting: a randomised 
control trial 
Clinical Trials Protocol 
02/04/2025 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
Description: An experiment exploring the perceived effectiveness of Nutri-score food labels with 
calorie labelling compared to calorie labelling only on food choice and consumption in a real-world 
setting 
Contributors: Amy Finlay, Andrew Jones, Rebecca Evans, Zoé Colombet, James Garbutt, Martin 
O’Flaherty, Zoi Toumpakari, Nick Townsend & Eric Robinson 
Category: Project 
Affiliated institutions: University of Liverpool, John Moores University, University of Bristol 
License: CC-By Attribution 4.0 International 
Subjects: Psychology, Life Sciences, Health Psychology  
Background:  
Data from the Food & You 2 survey conducted in 2022-2023 showed that between 60% and 72% of 
adults (according to age group) reported eating food out of home in the last four weeks while 
between 22% and 80% of adults reported ordering a takeaway in the last four weeks(1). 
Additionally, survey findings from 2024 suggest that 60% of UK adults eat food prepared outside of 
the home weekly(2). Individuals who eat out-of-home (OOH) food more frequently typically have 
poorer dietary quality due to a higher intake of energy and nutrients of concern (saturated fat, salt 
and sugar) and lower intake of fibre, dairy, fruit and vegetables(3). There is a need to improve the 
nutritional quality of meals selected by individuals in OOH settings. 
Interventions to improve eating OOH typically fall into three categories: structural (e.g. changing the 
presentation or availability of food items)(4), fiscal (e.g. changing the price of food items)(5) or 
informational (e.g. labelling food items)(6). Labelling is seen by consumers as the most acceptable 
type of policy for unhealthy commodities(7), and has been shown previously to prompt healthier 
food choices by consumers(8), and result in healthier offerings from outlets(9).  
Front of package (FOP) labels have been used in grocery store settings for some time. For example, 
in the UK multiple traffic light (MTL) labelling on packaged foods was introduced as a voluntary 
policy in 2013(10) while  Nutri-score (NS) labels were implemented as a voluntary policy in France in 
2017(11) and warning labels were mandated in Chile in 2016(12). A scoping review of FOP labelling 
strategies concluded that MTL, NS and warning labels were likely to be the most effective label types 
for informing consumers of the healthiness of food products(13), as opposed to informing 
consumers of guideline daily amounts. Warning labels highlight when a product is high in one 
specific nutrient (for example high in salt/high in sugar)(14), while MTL and NS use colour coded 
systems to summarise the healthiness of the product(15). Specifically, MTL labels report how various 
nutrients in a product (fat, saturated fat, sugar, sodium) compare to guideline daily amounts. Each 
nutrient is highlighted in red (signalling high content), amber (medium content) or green (low 
content)(16). In comparison, NS labels summarise the healthiness of a product as a whole and 
consider both positive and negative nutrients within the product (e.g., salt, saturated fat, fibre, 
protein). All items are categorised from A (Dark green - healthiest) to E (Red - least healthy) and 
highlighted in the corresponding colour(11). All three of these label types have been evaluated as 
high in Perceived Message Effectiveness (PME)(6), which is considered an early indicator of long-
term behaviour change(17), but NS labels were perceived as more credible by consumers than 
warning labels(6). 

NS labels, while first implemented in France (11), have since been adopted by a number of European 
countries(18). Evidence from online studies suggest that when NS labels are present, the nutritional 
quality of participant food choices is improved(19, 20), likely through decreasing the probability of 
choosing less healthy options while increasing the probability of choosing healthier options (6). A 
study in an experimental supermarket found similarly that NS labels improved the nutritional quality 
of a shopping cart when applied to three categories (breakfast cereals, sweet biscuits and 
appetizers)(21). When compared to pricing strategies, NS labelling was found to perform more 
effectively, through improving nutritional quality of selected foods(22). 
Research conducted in supermarkets in France found that the introduction of NS labels was 
associated with significantly improved nutritional quality of food shops (mean UK Nutrient Profiling 
Model (NPM) score lowered by -0.27, an improvement of 4.45%)(23). Effects were found to be 
greater for people making the least expensive purchases, the majority of whom were those with the 
lowest incomes. This suggests that such a policy could help to reduce social inequalities, a vital 
consideration for food policy(24). Comprehension of NS was high, with 92% of consumers able to 
rank items in order of healthiness correctly(23), demonstrating that such labels can be considered 
informative. A limitation of the existing research is that it typically fails to explore compensation. For 
example, whether there is a possibility of later compensation, e.g. through subsequent purchase or 
consumption of less healthy products.  
As NS has generally been considered a FOP label, to date there has been limited consideration of 
how this could be applied to the OOH food sector. A meta-analysis(25) of field studies of food 
labelling in a range of settings including cafeterias, supermarkets and a restaurant found that 
descriptive labels (e.g. calorie or other nutritional information) led to a directional overall reduction 
in unhealthy eating behaviour (selection/consumption of energy-dense, nutrient-poor foods), 
however this was not statistically significant. Conversely, evaluative labelling comprised of 
nutritional information alongside information to aid interpretation, such as colour coding (e.g. traffic 
light labels) or special symbols (e.g. warning labels/labels signifying healthier options) led to a 
significant reduction in unhealthy eating behaviour (effect size d=0.17). Greater effects are likely a 
result of increased drawing of attention and improved understanding of labels(6).  
Only one study has explored how NS impacted food choices in a work cafeteria(26). This study used 
a non-randomised design with no control group and found introduction of NS was associated with 
improved nutritional quality of food choices (UK NPM score -0.22; 11.5%), and lower selected energy 
content. However, due to data being gathered through receipts, this study did not collect 
information on consumption or demographic characteristics, so individual differences in impact of 
NS could not be explored. The impact of NS labels in a full-service restaurant setting has not yet 
been tested. Recent research has considered the role of expectations in determining the potential 
impact of NS labels(27). This study found that due to underlying expectations of healthiness, 
effectiveness of NS may be reduced. For example, if a product was anticipated to be the least 
unhealthy category (‘E’) but was rated healthier (e.g. ‘D’), there may be increased selection of the 
product marked ‘D’ due to reduced guilt around eating the product. Therefore, labelling combined 
with expectations may result in less healthy food selection. Due to this uncertainty surrounding NS 
labelling, it is important we test the effectiveness of NS in the OOH food sector.  
There have been a small number of cross-country studies assessing various food labels on consumer 
understanding and choice that have included UK participants(28, 29), and one online study of UK 
participants exploring the impact of labelling types on the ability of participants to rank packaged 
food items in order of healthiness(30). However, there is no research we are aware of that has 
tested NS labels on food choice in a UK OOH context.  

The present study will be conducted in multiple independent outlets in the UK OOH food sector and 
examine the impact of NS menu labelling. Participants will visit an outlet and be randomized to order 
from the restaurant’s menu with calorie information or a menu with calorie information and NS 
labelling. The main objective of this study is to assess differences in PME according to labelling 
condition. Secondary objectives are to measure the effect of NS labels on the nutritional quality of 
food selected (UK NPM scores), energy content of the meal (both ordered and consumed) and 
likelihood of selecting a healthier and a less healthy option. Whether impacts of NS labelling differ 
based on participant characteristics will be explored (Socioeconomic Position (SEP), food choice 
motives) and we will also examine later food intake to assess whether there is any evidence of 
between condition differences (e.g., compensating for healthier meal choice in the NS condition by 
consuming less healthy food later in the day).  
Study Information 
Hypotheses:  
Participants in the NS with calorie labelling condition will score higher on PME relating to the menu 
compared to participants in the calorie labelling only condition.  
Participants in the NS with calorie labelling condition will order a meal with greater nutritional 
quality compared to participants in the calorie labelling only condition. 
Participants in the NS with calorie labelling condition will order fewer calories from food overall 
compared to participants in the calorie labelling only condition. 
Participants in the NS with calorie labelling condition will be more likely to choose healthier items 
(categorised as A/B) from the menu, and less likely to choose less healthy items (categorised as D/E) 
from the menu compared to participants in the calorie labelling only condition. 
Design Plan 
Study type: Experiment - A researcher randomly assigns treatments to study subjects; this includes 
field or lab experiments. This is also known as an intervention experiment and includes randomised 
controlled trials. 
Blinding: Participants will not know the treatment group to which they have been assigned. 
Is there any additional blinding in this study? To attempt to reduce the likelihood of aim guessing, 
participants will be recruited to a study described as ‘A study of consumer behaviour in different 
restaurants’.  
Study design: Businesses are being actively recruited for this study. We aim to have a minimum of 
two outlets available for participants to visit. This study is a randomised controlled trial using a 
between-subjects design. Participants will be asked to visit a restaurant to eat lunch and complete 
some questionnaires. Participants will select one of the available restaurants to visit and will be 
randomly assigned to one of two conditions: Calorie labelling only or NS with calorie labelling. Later 
intake (over the rest of the day, after the lunch time study session) will be self-reported by 
participants. If one outlet is more popular than the other outlet(s), and we are not obtaining a 
similar number of participants for the outlets on offer, then we will actively recruit participants to 
each of the outlets to ensure a similar number of participants are recruited to each outlet tested.  

Randomisation: Participants will be randomised to one of the two conditions. Data collection days at 
each of the outlets will be randomised as either NS with calorie labelling or calorie labelling only. 
Data collection days will be randomly assigned to condition using the RANDBETWEEN function in 
excel.  
Sampling Plan 
Existing Data: Registration prior to creation of data 
Explanation of existing data: N/A 
Sample 
Data collection procedures: We will use an existing participant database consisting of local volunteer 
participants recruited through social media advertising. Only participants who have not taken part in 
previous similar research conducted by the appetite group at the University of Liverpool will be 
contacted. If required, more participants will be recruited from the local community (e.g. adverts on 
social media/posters in the university). Participants who sign up to the study can bring up to 4 guests 
with them to also take part. Tables of 5 participants were determined as the upper limit as it was 
deemed a manageable size for researchers to effectively monitor individual orders. Over the course 
of the study, we will attempt to ensure our sample is representative of the UK population in terms of 
gender (50% male, 50% female), age (36% aged 18-39; 64% aged 40+(31)), and SEP - education level 
(50% level 3 and above (2+ A-levels or equivalent, not including apprenticeships(32)).  
 Inclusion criteria:  
• 
Can visit a restaurant in Liverpool city centre  
• 
Regularly eat food prepared out of the home (from restaurants, cafes, fast food etc., at least 
once a month) 
• 
Over the age of 18 years 
• 
Fluent English speaker 
Exclusion criteria:  
• 
Pregnant/breastfeeding 
• 
You have been diagnosed with a current or historic eating disorder 
We will check whether participants have any food allergies prior to taking part in the study and 
ensure that if there are allergies this information is communicated to the food outlet by a 
researcher. All participants will be aware of the nature of the study (i.e. consuming food/drink in a 
food outlet) - this will be explicitly stated in the Information Sheet. The information sheet will also 
draw attention to the potential risks of taking part if a participant has a food allergy and that they 
should consider this before deciding whether to visit the food outlet. 
Procedure:  
Participants will be contacted via email and asked to complete a short online screening 
questionnaire. Screening will ensure participants meet the inclusion criteria.  
Participants that pass the screening questionnaire will be contacted to book the date and time of 
their meal at one of the food outlets in Liverpool city centre. There will be 6 time slots available over 
lunch time (between 12 and 2.30). Participants will be able to bring up to four guests with them to 
take part in the study. All guests must meet the inclusion criteria. 

Each study day will be randomised to one of the two conditions: 
• 
Calorie labelling only condition  
• 
NS with calorie labelling condition 
Upon arrival, all participants will be asked to provide verbal consent to take part in the study. The 
menu randomised according to day using the RANDBETWEEN function in excel (Calorie labelling only 
or NS with calorie labelling) will be provided to all participants, and they will order their meals and 
drinks with the wait staff when they are ready.  
Participants will be provided with their lunch. Before serving foods, away from the view of 
participants, researchers will take a picture of each plate of food. Each picture will be uploaded to a 
personal folder labelled with each participant ID.  
When they have finished each food course, plates will be cleared by wait staff and taken to another 
part of the restaurant, away from view of the participants. Researchers will take photographs of the 
plates to document any food left over, and images will be uploaded to participant personal folders. 
Participants will each pay for their meal once they have finished.  
Participants will be asked to complete a questionnaire on an iPad to collect demographic 
information, assess health food choice motives, PME relating to the menu labels and to guess the 
aim of the study. Participants will also be asked to confirm the food items they ordered, whether 
they had any additional components such as condiments, and to report whether they shared any 
items with others at the table and if so, how much was shared. Participants will be given clear 
examples of how to report this. Upon completion of the study session, participants will complete a 
payment form to receive monetary reimbursement. This reimbursement will compensate 
participants for travel and time.  
The next morning, participants will be emailed with a link to Intake 24, an online programme for 
dietary recall. They will be asked to report anything that had been eaten after the lunch time meal 
the previous day. Following this, all participants will be fully debriefed. 
The restaurants in which this study will take place will be independent restaurants in Liverpool city 
centre. As they are small, independent businesses, they are not required to report any nutritional 
information. Researchers liaised with restaurant owners, chefs and front of house staff to gather the 
required menu information (ingredients, cooking method) to calculate the nutritional content of 
meals using Nutritics(33), a platform which can be used to estimate the nutritional content of meals 
using validated methods. The NS values for all items on the food menus of the outlets were 
calculated using the NS spreadsheet available online (34). There are currently three outlets where 
data collection is planned to take place. These are all in Liverpool city centre and are 1) a plant-based 
café, 2) a café in the university campus and 3) a street-food inspired café.  
Variables 
Manipulated variables: Whether participants are provided with a calorie labelled menu or a menu 
where each item is also labelled with a NS classification from A (healthiest) to E (least healthy). 
Adapted NS: The NS classification was created in France to apply to packaged food products, and the 
calculations are made based on energy, nutrients (saturated fat, sugar, salt, fibre, protein) and fruit, 
vegetable and nut content per 100g of the food product. Fruit, vegetable and nut content for each 
menu item was estimated by two researchers individually. Any disagreements were resolved by 

discussion. In order to accurately categorise food products in an OOH venue, some adaptations were 
made to account for the serving size of items. Cut off values for energy content (kcal) based on UK 
nutrition guidance were used according to menu category. If the kcal content of items was below the 
lower cut off value, items were upgraded a NS value (e.g. from C to B). If the kcal content of items 
was above the higher cut off value, items were downgraded a NS value (e.g. from C to D) 
• 
Starters and sides 280kcal/600kcal 
• 
Mains 600kcal/860kcal 
These cut-off values were informed by UK Public Health guidance, where available. 280kcal was 
deemed a suitable size for a small dish to accompany a main meal, based on NHS guidance for 
snacks(35). 600 kcal was selected as the recommended energy content for main meals(36), 
therefore was deemed suitable for main meals but excessive for starters and side dishes. Above 860 
kcal was deemed excessive for main meals, as it would exceed the average calorie guideline for a 
main meal set out in the calorie reduction technical report(37).  
As an additional measure to accurately represent the healthiness of items, if any items contained 
≥100% of the average guideline daily allowance of energy, saturated fat, salt, or sugar, it was not 
possible for the item to score higher than an E.  
On the NS labelled menus, there will also be a short description of how the labels are calculated:  
“Nutri-score represents the overall healthiness of menu items on a scale of A (healthiest) to E (least 
healthy). This score is calculated according to the content of energy and key dietary nutrients (e.g. 
saturated fat, sugar, salt, protein, fibre). 
This does not differentiate between fructose (i.e. sugar found in fruit) and refined sugar or directly 
account for vitamin/mineral contents or level of processing.” 
 
 
 
 
Measured variables:  
Perceived Message Effectiveness 
An adapted version of the University of North Carolina PME scale(38) will be used to measure health 
concern, product attitude, and discouragement of item consumption in response to the food menu. 
Participants will be given the menu they ordered from to look at. All participants will answer 3 
questions using a Likert scale ranging from 1 – 5 anchored by “not at all” and “a great deal”. The 
mean response to the three items will be calculated. PME is used as an early indicator of a health 
message’s potential to change behaviour (e.g., reduce selection of less healthy items)(17). The scale 
has been used previously to identify the potential impact of food labels and is predictive of long-
term behaviour (39-45). 
NS label of each item selected (A,B,C,D,E).  
A NS category value will be recorded for each item selected by participants. 
Nutritional quality of each item and for the full meal 

Nutritional quality for meal choices will be calculated using the UK NPM scoring system(46). This 
calculates a score (continuous variable) for a product by deducting a total score for positive nutrients 
from a total score for negative nutrients. A lower score represents greater nutritional quality and a 
higher score represents poorer nutritional quality.  
We will calculate the mean NPM score weighted by energy content of items for each participant. 
This will ensure that the NPM score of main dishes will be weighted higher than that of starters or 
sides (assuming energy content of selected main is higher than any starters or sides), leading to a 
more representative overall NPM score for food orders. This will be done using the weighted.mean 
function in R(47). This function multiplies each value (i.e. NPM scores for individual items) by its 
corresponding weight (kcal content of individual items), sums all items and then divides this by the 
sum of the weights.  
Energy content of all food ordered 
The sum of energy (kcal) across all foods ordered for the meal will be calculated 
Energy and nutrients consumed 
Researchers will take pictures of plates before and after each item is given to participants. 
Researchers will estimate the percentage of each dish consumed, by estimating the percentage of 
individual meal components that have been eaten. Estimations will be guided by the information 
available from the nutritional analysis of items, which details the proportion of the meal that is 
made up by individual components. For example:  
Fish and chips: Total energy comes from 41% fish, 41% chips, 12% mushy peas, 5% tartare sauce, 1% 
watercress. 
• 
If 50% of chips are left (20.5% total) and 1/3 mushy peas left (4% total), then 24.5% of the 
meal was not eaten and 75.5% of the meal was eaten.  
Participants will also be asked whether they shared any of their meal with someone else and this will 
be taken into account when making percentage estimates. A random 10% of percentage estimates 
will be performed by a second researcher to measure reliability.  
Energy and nutrient consumption will be calculated by multiplying the total energy/nutritional 
content of food items selected/consumed by the estimated proportion of the item consumed. 
Nutrients explored will be salt, sugar, fat, saturated fat, protein and fibre.  
Later intake 
The morning after participants take part in the study, they will be emailed with a link to complete a 
dietary recall survey (via intake 24, https://intake24.co.uk/). Participants will report everything they 
ate after the study session up until they went to bed. They will be asked to provide as much detail as 
possible on what they had for dinner, snacks, and drinks after the study session. We will estimate 
based on data from Intake 24, later consumption (kcal, salt, fat, saturated fat, sugar, protein, fibre). 
Participant characteristics 
To characterise the sample and present outcomes by individual participant variables, participants 
will be asked to report their gender, age and ethnicity. Height and weight data will also be collected 
to calculate body mass index (BMI), so participants can be classified into underweight, healthy 
weight, overweight or obesity.  

Highest educational qualification: measure of socioeconomic position (SEP) 
Participants will be asked to report their highest educational qualification. If they are still studying, 
they should report the diploma they are currently studying for. The categories provided will be: 
• 
Less than high school 
• 
High school completion 
• 
College or foundation degree 
• 
Bachelor’s degree 
• 
Master’s degree 
• 
Doctoral or professional degree  
Frequency of eating OOH 
Participants will be asked to report how often they eat food prepared OOH. They will be provided 
with an explanation of what constitutes OOH (e.g., “How often over the past year on average have 
you eaten food prepared out of the home? This includes food from a restaurant, café, pub or similar 
venue”). The response options will be:  
• 
Not in the last year 
• 
Less than once per month 
• 
1-3 times per month  
• 
1-2 times per week 
• 
3 times per week or more  
Measure of health food choice motives 
The Food Choice Questionnaire(48) is comprised of nine factors (health, mood, convenience, sensory 
appeal, natural content, price, weight control, familiarity & ethical concern). We will include the 
health motive scale into our questionnaire to assess whether the value of health is associated with 
the impact of NS labelling on participant food choices. 
Attention check 
An attention check will be placed in the questionnaire: “This question is an attention check, so 
please answer truthfully. How many times have you visited the planet Mars? Several times / Just 
once / Never”.  
Correct answer: Never 
Aim guessing 
Participants will be asked what they believe the aims of the study to be. Anyone that guesses the 
study aims to be investigating the influence of food labels on food choice or consumption will be 
coded as being aware of study aims. Two researchers will independently code awareness of aims 
and any discrepancies will be judged by a third researcher.  
Label awareness/understanding 
Participants will be asked the following questions using a funneled approach whereby questions will 
be presented one by one: 
1) Did you notice any labels or additional information on your food menu? (Yes/No) 
[If no, skip to Q5] 

2) Which labels/information did you see on the food menu? (select one of the following) 
 
 
 
 
 
[If incorrect, skip to Q5] 
3) Did the labels/information influence your food selection? (Yes/No) 
[If no, skip to Q5] 
4) How did the labels/information influence your food selection? (I chose a meal with a 
healthier classification/I avoided a meal with a less healthy classification/Other)  
 
5) Nutri-score is a labelling strategy used in several European countries on food packaging. 
Nutri-score represents the healthiness of menu items on a scale of A (healthiest) to E (least 
healthy). This score is calculated according to the amount of healthy and unhealthy 
nutrients.  
 
 
 
If the UK government introduced a policy requiring the use of a ‘Nutri-score’ system on food 
menus, how would you feel? (Likert scale ranging from 1 – 5 anchored by “strongly oppose” 
and “strongly support”) 
 
Study flow 
Recruitment 
• 
Participants will be identified via an existing database of 
individuals who expressed interest in taking part in research or 
through social media advertisement. 
• 
Prospective participants will be emailed with a brief study 
overview (consumer behaviour at different restaurants) and a link 
to complete the screening questionnaire (Appendix A). 
• 
Throughout the study (e.g. after 25%, 50% and 75% completion 
achieved), we will examine the characteristics of participants to 
ensure the sample is broadly representative of the UK population. 
If this is not the case (e.g. there are 70% female participants) then 
recruitment will be altered to source the participants needed (i.e. 
to recruit an equal number of male participants). This will be done 
through targeted advertising.  
Information sheet 
and informed 
consent 
• 
Eligible participants will be e-mailed an information sheet 
(Appendix B) and consent form (Appendix C). Participants will be 
told they can ask any questions about the study via e-mail. 
Calorie 
information 
None of the above 
labels/information 

• 
The researcher will schedule a study visit day. For each of the 
restaurants, there will be 6 available lunch time study slots 
scheduled every 30 minutes between 12pm and 2.30pm. 
Participants may bring a maximum of four guests aged 18 years or 
older to the restaurant, and must confirm the final number of 
participants, and that all guests meet inclusion criteria.  
• 
As the additional guests would not have received an online 
information sheet and consent form, upon arrival at the 
restaurant all participants will be provided with information by 
the researcher and will give verbal consent. The researcher will 
answer any questions prior to the study. 
• 
Study days will be randomised as calorie labelling only or NS with 
calorie labelling condition. 
Meal choice task 
• 
Participants will be given a participant number which must be 
entered in the follow-up questionnaire they complete.  
Control condition 
Participants will 
receive a calorie 
labelled menu 
without NS labels. 
The menu will 
include a 
statement that 
‘Adults need on 
average 2000 kcal 
per day’. 
Experimental condition 
Participants will receive a menu with each item 
labelled with calorie content and a NS value (A to E, 
where A is the healthiest in dark green and E is the 
least healthy, in red). The menu will include a 
statement that ‘Adults need on average 2000 kcal 
per day’. Text at the bottom of the menu will show 
the full Nutri-score diagram and read:  
“ 
 
 
 
 
 
Nutri-score represents the overall healthiness of 
menu items on a scale of A (healthiest) to E (least 
healthy). This score is calculated according to the 
content of energy and key dietary nutrients (e.g. 
saturated fat, sugar, salt, protein, fibre). 
 
This does not differentiate between fructose (i.e. 
sugar found in fruit) and refined sugar or directly 
account for vitamin/mineral contents or level of 
processing” 
• 
The participants will be asked to order lunch from the menu. The 
procedure of placing orders will be finalised with the restaurant 
staff. 
• 
When meals are ready, researchers will take a picture of each plate 
of food and serve to participants. A second photo of each plate will 
be taken when meals are finished, and plates are cleared.  
Post-meal 
assessments 
(Qualtrics)  
• 
After finishing their meal, participants will be provided with an 
iPad to complete a follow-up questionnaire (Appendix D), which 
will ask them to guess the aim of the study, collect information on 
perceived message effectiveness, health food choice motives, 

demographic characteristics, and label awareness and 
understanding. 
Reimbursement 
• 
Participants will pay for their meals individually before being asked 
to complete a payment form.  
• 
Participants will receive reimbursement for their time and travel 
and serve as an incentive for people from different SEP strata to 
participate.  
Later intake 
• 
After the restaurant visit (the next morning), participants will 
receive a link to Intake 24, an online programme used for dietary 
recall. This will be used to estimate intake for the remainder of the 
day after the study session.  
Debrief 
• 
Participants will be sent a debrief sheet which will detail the full 
aims of the study. (Appendix E) 
Analysis Plan 
Participant characteristics: 
Only participants who completed the restaurant visit (consumed a meal and completed the 
questionnaire) will be included in analysis. We will report analyses with any participants who guess 
the aims of the study included and excluded. We will identify any cases where the height and weight 
data provided has resulted in an implausible BMI value (<12kg/m2 and >100kg/m2(49)) and exclude 
these subjects from analysis involving BMI. 
Participant characteristics will be presented in a table. Data will include age, gender, ethnicity, BMI 
and highest education level. Continuous variables will be summarised by means and standard 
deviations, categorical variables will be summarised by counts and percentages. The descriptives 
table will report variables overall and split by condition and outlet.  
Descriptive analyses: 
We will report quantitative questionnaire findings and main outcomes by condition in a table. This 
will consist of: frequency of eating OOH food, health food choice motive scores, label 
awareness/understanding, PME, UK NPM score, kcal selected and consumed and the proportion of 
participants selecting food with each label (A-E). As above, these variables will be reported overall 
and split by condition and restaurant. 
Anticipated primary analyses:   
Shortly after starting data collection and prior to any interim analyses, we will finalise the full 
analysis plan and publish this alongside the protocol on the Open Science Framework. The 
anticipated analysis approach is briefly stated below.  
PME 
A linear mixed model will be used to assess the impact of labelling condition (calorie labelling 
only/NS with calorie labelling) on PME relating to the food menu (a mean score).  
Nutritional quality of ordered meal (UK NPM score) 

A further Linear mixed model will be conducted to explore the impact of labelling condition (calorie 
labelling only/NS with calorie labelling) on the nutritional quality of the participant’s full meal (mean 
weighted UK NPM score: linear outcome variable).   
Secondary analyses:  
Likelihood of selecting a healthier option (A/B)  
Any participants who have selected a healthier item (A/B) as part of their meal will be coded as 1 
and participants who have only selected options with a C/D/E value will be coded as 0. We will 
conduct a logistic regression to test whether NS labelling (Y/N) is associated with the likelihood of 
selecting a healthier item. 
Likelihood of selecting a less healthy option (D/E) 
Similar to the above, any participants who select a less healthy item (D/E) as part of their meal will 
be coded as 1, and participants who have only selected options with a A/B/C value will be coded as 
0. We will conduct a logistic regression to test whether NS labelling (Y/N) is associated with the 
likelihood of selecting a less healthy item.  
Energy and nutrient content consumed at lunch 
Similar to primary analyses, we will explore the impact of NS labelling on total energy and nutrient 
content of food consumed (linear outcome variables) through n=8 linear mixed models. The 
nutrients explored will be salt, sugar, fat, saturated fat, protein, fibre and fruit vegetable and nut 
content.  
Transformations: N/A 
Inference criteria: Results for primary analyses will be considered significant at p<0.05, and to 
account for multiple comparisons, secondary analyses will be considered significant at p<0.01.  
Data exclusion: If participants leave the restaurant study session without ordering food their data 
will be excluded from analyses. 
Missing data: If participants do not complete the dietary recall survey, and therefore do not provide 
data of later intake, then we will impute the missing data for this variable. Any missing data for other 
outcomes (e.g., PME) will also be imputed. We will complete multiple imputation with 5 imputed 
datasets(50) in R using the ‘mice’ package. Imputation will be reported in line with published 
guidance(51). 
Exploratory analysis:  
Other:  
Sample size:  
We conducted a simulation to estimate sample size required for two primary outcomes: PME and 
NPM scores. Our simulation was based on previous research and knowledge of the outlets 
confirmed for data collection.  
We simulated running the study with 20 participants a day for 20 days (400 total data points). For 
PME, we estimated from previous research that we may have an intercept PME value of 1.85 (SD: 
1.08), with an intervention effect of 1 (the intervention group will have PME values 1 unit greater 
than the control group on average, based on previous research(52)), and minimal difference in PME 

scores between the two outlets (0.2). We also assumed ICC of approximately 0.200, and a standard  
deviation of the random intercept of eating group in a mixed model of 1. Across 200 simulations 
using a regression model clustered by day, we would have 94% power (95% CI 89.75, 96.86) to 
detect differences in PME between the two conditions.  
For NPM scores, we calculated using the two confirmed outlet menus, that we may have an 
intercept NPM score of -0.27 (SD: 3.29) with an intervention effect of 0.22 (the intervention group 
will select meals with with greater nutritional quality, shown by a 0.22 higher NPM score) based on 
previous research(26) and a mean difference between the two outlets of 1.4 (the difference in mean 
NPM scores for the two outlets). We also assumed ICC of approximately 0.819, and a standard 
deviation of the random intercept of eating group in a mixed model of 1. Across 200 simulations 
using a regression model clustered by day we would have 88.5% power (95% CI 83.25, 92.57) to 
detect differences in NPM scores between the two conditions. 
Due to uncertainty over size of anticipated effects and available resources, we will increase the 
above desired maximum sample size (400) by 12.5% to 450 participants.  
Stopping rule 
Prior to the study we do not know with certainty what the rate of participant recruitment will be, 
and effect size estimates have a degree of uncertainty. To balance the trade-off between costs (e.g., 
in research time, participant burden) and likelihood of the study providing convincing evidence, we 
will conduct interim analyses to assess whether the results are convincing enough to conclude that 
effects on PME and nutritional quality of food order are present(53). The interim analyses will 
examine the effect sizes of these two primary outcomes and observed statistical significance. We 
will also calculate Bayes Factors to assess the strength of evidence for the experimental vs null 
hypotheses.  
We will conduct the interim analysis when we have obtained approximately 50% of the full sample 
(224 participants, ~112 completers in each condition). If at this point, the data suggests that it is 
extremely unlikely that either of the predicted effects would be observed up to maximum sample 
size capacity (described above), and if Bayes Factors suggest there is evidence for the null hypothesis 
(BF10 < 0.3) then we will cease data collection and conduct full planned analyses.  
However, if the observed effect size suggests that an effect size statistically detectable at N=450  is 
present but is not statistically significant at interim, or Bayes Factors do not provide support for 
either the null or alternative hypothesis (BF10 > 0.3 and < 3), we will continue data collection to 
recruit the largest possible sample size and adjust p values (dividing by 2 for outcomes examined at 
interim to account for multiple analyses) to account for error rate inflation for final full sample 
analyses.   
Due to the sample size required and potential difficulties in recruiting sufficient numbers for each 
stratum (e.g., lower SEP individuals, males) we may need to adjust plans during data collection. If we 
experience recruitment difficulty during the first month of data collection, we will prioritise 
stratifying by SEP ahead of age and sex, as individuals with a higher education level are more 
motivated by health when making food choices (16). 
 
 
 

Appendix A: Recruitment text 
This is a study exploring eating out at restaurants. If you wish to take part, you will need to complete 
a short screening questionnaire to ensure you are eligible to take part.  
If you would like to take part, please make sure: 
• 
You currently reside in Liverpool and can visit a restaurant in the city centre for lunch on a 
weekday. 
• 
You regularly eat food prepared out of the home (from restaurants, cafes, fast food, etc.) 
• 
You are over the age of 18 years 
• 
You are a fluent English speaker 
• 
You are not pregnant/breastfeeding 
• 
You have no current or historic eating disorder 
If you are eligible, you will be asked to come to a restaurant in Liverpool city centre for lunch at a 
pre-specified time between 12 and 2:30pm on a weekday. You can bring up to 4 friends with you to 
take part. All participants must meet the above criteria.  
You will be able to choose a meal from a full restaurant menu and asked to complete a couple of 
short questionnaires. You will each pay for the meal yourself and receive monetary reimbursement 
of £20 for your time once the study is complete. This reimbursement should cover meal and travel 
costs associated with taking part in the study.  
The following morning you will be sent a link to follow to report what you ate for the rest of the day 
following the meal.  
To complete the screening questionnaire, please follow the link below:  
[insert link] 
 
 
 
 
 
 
 
 
 
 
 
 
 

Appendix B: Participant information sheet 
 
 
A study on consumer behaviour in different restaurants 
 
You are being invited to participate in a research study. Before you decide 
whether to participate, it is important for you to understand why the research is 
being done and what it will involve. Please take time to read the following 
information carefully and feel free to ask us if you would like more information 
or if there is anything that you do not understand. We would like to stress that 
you should only agree to take part if you want to. 
 
What is the purpose of the study? 
The purpose of the study is to understand consumer habits in different types of 
restaurants. 
  
Why have I been chosen to take part? 
   We are recruiting volunteers who fulfil the following criteria: 
• You can visit a restaurant in Liverpool city centre for lunch on a weekday. 
• You regularly eat food prepared out of the home (from restaurants, cafes, etc.) 
• You are over the age of 18 years 
• You are a fluent English speaker 
• You are not pregnant/breastfeeding 
 
Please be aware of the potential risks of taking part if you have a food allergy. These 
risks are no higher than if you were to eat food at a restaurant generally, however, 
please consider this before deciding whether to take part in the study. If you do have a 
food allergy and still wish to take part in the study, please inform the researcher of your 
allergy so they can ensure the restaurant are aware.  
 
Do I have to take part? 
No. Participation in this research is completely voluntary. You are free to 
withdraw at any time without explanation and without incurring a disadvantage. 
 
What will happen if I take part? 
Following a short online screening questionnaire, you will be required to come 
to a restaurant in Liverpool city centre for your lunch on a weekday. You can 
come alone or with up to four friends. You will be asked to order your meal and 
then provide some information about yourself (e.g., age, gender). You will then 
be served your lunch. When you have finished your food you will be asked to 
complete another short questionnaire and pay for your meal. The following 
morning you will be sent a link to follow where you will be able to report what 
you ate for the rest of the day following the lunch time meal. So that your 
awareness of the study hypotheses does not affect your behaviour in the study 
we will provide more detailed information about the study aims at the end of 

the study. If you feel uncomfortable about this then you are free not to 
participate in this study. The study should take approximately 60-90 minutes, 
depending on how long you take to eat your lunch. You will be reimbursed for 
your time, the reimbursement provided should cover meal costs plus travel 
expenses incurred.  
 
How will my data be used? 
The University processes personal data as part of its research and teaching 
activities in accordance with the lawful basis of ‘public task’, and in accordance 
with the University’s purpose of advancing education, learning and research for 
the public benefit. University of Liverpool employee Amy Finlay 
(amy.finlay@liverpool.ac.uk) acts as the Data Protection Officer for this study 
and any queries relating to the handling of your personal data can be sent to 
her. Further information on how your data will be used can be found in the table 
below. 
  
Are there any risks in taking part? 
How will my data be collected? 
Through measurement of in-person tasks, 
questionnaires and food ordered.  
How will my data be stored? 
On a password protected computer server. 
How long will my data be stored for? 
Your personal data will be stored for up to 28 
days and then deleted. All other information will 
be stored indefinitely. 
What measures are in place to protect the 
security and confidentiality of my data? 
We will store all data on password protected 
computer servers and we never share any of 
your personal data outside of the research team 
for this project.  
Will my data be anonymised? 
After the study your personal information will be 
stored separately from your other questionnaire 
responses to create an anonymised data set. 
After 28 days all personal information will be 
deleted, but up to this point you can contact us 
and ask to see your information or have it 
deleted. 
How will my data be used? 
Your anonymised data will be combined with 
other participants’ data in order to be analysed. 
Who will have access to my data? 
The research team for this project will have 
access to your data. 
Will my data be archived for use in other 
research projects in the future? 
After the research team have anonymised your 
data and completed this research project, they 
will place the anonymised data sets on an 
archive (e.g. Open Science Framework) in case 
any other researchers want to use it for future 
research purposes.  
How will my data be destroyed? 
Your 
personal 
data 
will 
be 
destroyed 
electronically (deleting the files and removing 
them from the computer server).  

There are no anticipated risks to you if you take part in the study. 
 
Are there any benefits in taking part? 
There are no direct benefits, other than the monetary reimbursement. 
 
What will happen to the results of the study? 
We intend to publish the results from this study in a scientific journal. However, 
as explained above any personal information you provide is deleted before this 
and you would therefore not be identifiable in report. If you are interested in 
the results of the study, please let us know and we will share the results of the 
study with you when we publish it. 
 
What will happen if I want to stop taking part? 
You are under no obligation to take part in this study; it is completely your 
choice. If you do decide to take part, you are free to withdraw at any time and 
without giving any reason or explanation. Data collected up until the period you 
withdraw may be used, but only if you are happy for this to be done. Otherwise 
you may request that your data be destroyed and no further use is made of 
them. We cannot guarantee payment if you do not complete all three visits.  
 
What if I am unhappy or if there is a problem? 
If you are unhappy, or if there is a problem, please feel free to let us know by 
contacting Amy Finlay or Eric Robinson (contact details below) and we will try to 
help. If you remain unhappy or have a complaint which you feel you cannot come 
to us with then you should contact the Research Governance Officer on 0151 794 
8290 (ethics@liv.ac.uk). Please provide details of the name or description of the 
study (so that it can be identified), the researcher(s) involved, and the details of 
the complaint you wish to make. 
 
Who can I contact if I have further questions? 
Please contact the principle investigator: Amy Finlay (amy.finlay@liverpool.ac.uk) 
2.80, Eleanor Rathbone Building 
University of Liverpool, 
L69 7ZA, 
 
or the senior researcher: Prof. Eric Robinson (robinsoe@liverpool.ac.uk) 
 
I confirm I have read the information sheet 
o Yes 

Appendix C: Consent form 
 
 
 
A study of consumer behaviour in different restaurants 
I confirm that I have read and have understood the information sheet for the 
above study. I have had the opportunity to consider the information, ask 
questions and have had these answered satisfactorily. 
 
I understand that taking part in the study involves completing questionnaires 
and ordering and eating lunch in a restaurant. 
 
I understand that my participation is voluntary and that I am free to stop taking 
part and can withdraw from the study at any time without giving any reason and 
without my rights being affected. I also understand that I have the right to lodge 
a complaint. 
 
I understand that the information I provide is for research purposes and it will be 
held securely in line with data protection requirements at the University of 
Liverpool. In addition, I understand that personal information collected about 
me that can identify me will never be shared beyond the study team. 
 
I understand that shortly after completing the study, researchers will keep my 
personal data and store it separately from my other questionnaire responses for 
up to 28 days on a computer, so that my anonymised questionnaire responses 
can later be deposited in an online data archive for sharing and used by other 
authorised researchers to support other research in the future. 
 
I understand that I can ask for access to any of the information I provide and I 
can request the destruction or alteration of that information if I wish for up to 
28 days after participating in the study. I understand that following this I will no 
longer be able to request access to or withdrawal of the information I provide 
because this information will have been deleted. 
 
I provide my consent as a legal basis for the processing of my data as detailed 
previously, including the purposes of data processing, recipients of data and the 
right to withdraw my data. 
 
I agree and consent to take part in the above study 
 
o Yes 

Appendix D: Follow up questionnaire  
1. How comfortable did you feel in this restaurant? 
 Very uncomfortable  
 Slightly uncomfortable 
 Neutral 
 Comfortable 
 Very comfortable 
 
2. Was this restaurant representative of restaurants you normally eat in?  
 Yes 
 No 
 
3. Would you eat in this restaurant again?  
 Yes 
 No 
 Maybe 
3a. Please elaborate on the reasons behind your answer to the previous question. 
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________ 
 
4. What do you think the aim of this study was?  
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________ 
 
5. Did you share any of the food or drink items? 
 Yes 
 No 
5a. [if yes] What items were shared? Please give an estimation in % of how much of each item was 
shared and specify what was (i) given to others and (ii) received from others. 
 
Example response: Potato bites, 20% given to others. Greek salad, 10% received from others.  
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________ 
 

6. Did you add any condiments (e.g., sauce, salt, pepper) to your food? 
 Yes 
 No 
 
6a. [if yes] What condiments did you add? Please give an estimation in teaspoons of how much of 
each condiment was added. 
Example response: ½ teaspoon of salt 
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________ 
 
7. [Health food choice motives measure] 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 
1 
Is high in fibre and roughage 
o 
 
o 
 
o 
 
o 
 
2 
Is nutritious 
o 
 
o 
 
o 
 
o 
 
 
This is an attention check.  
Please select the answer (2) ‘A little important’ 
o 
 
o 
 
o 
 
o 
 
3 
Contains a lot of vitamins and minerals 
o 
 
o 
 
o 
 
o 
 
4 
Is high in protein 
o 
 
o 
 
o 
 
o 
 
5 
Keeps me healthy 
o 
 
o 
 
o 
 
o 
 
6 
Is good for my skin/teeth/hair/nails etc. 
o 
 
o 
 
o 
 
o 
 
 
8. This is an attention check. How many times have you visited the planet Mars? 
o Several times 
o Just once 
o Never 
 
9. What is your age (in years):  
 
10. What is your sex? A question about gender identity will follow 
 Male 
 Female 
 
11. Which of the following best describes your gender? 
 Man 

 Woman 
 Non-binary 
 Other 
 Prefer not to say 
 
12. What is your highest educational qualification? If you are a student please select the qualification 
being studied for. 
 Less than high school 
 High school completion 
 College or foundation degree 
 Bachelor’s degree 
 Master’s degree 
 Doctoral or professional degree  
13. Please select your ethnicity:   
 White English/Welsh/Scottish/Northern Irish/British 
 White Irish 
 Any other White background 
 White and Black Caribbean 
 White and Black African 
 Any other mixed/multiple ethnic background please describe  
 Indian 
 Pakistani 
 Bangladeshi 
 Chinese 
 Other Asian 
 African 
 Caribbean 
 Arab 
 Any other ethnic group 
 
14. What is your weight 
 In KG ________ 
 In Stone and pounds __________ 
 Prefer not to say 
 
15. What is your height  
 In centimetres__________ 
 In feet and inches _________ 
 Prefer not to say 
 

16. How often, on average, over the past year have you eaten out (e.g., at a restaurant, café)? 
 Not in the last year 
 Less than once per month 
 1-3 times per month 
 1-2 times per week 
 3 times per week or more 
 
 
17. Did you notice a label on the food menu? [If no, skip to Q21] 
 Yes 
 No 
18. Which labels/information did you see on the food menu? (select one of the following) [If 
incorrect, skip to Q21] 
 
 
 
 
 
 
 
 
 
 
 
19. Did the label/information influence your food selection? (Yes/No) [If no, skip to Q21] 
 Yes 
 No 
 
20. How did the label/information influence your food selection?  
a. I chose a meal with a healthier classification 
b. I avoided a meal with a less healthy classification 
c. Other 
 
None of 
the labels 
shown 
Calorie 
information 

21. Nutri-score is a labelling strategy used in several European countries on 
food packaging. Nutri-score represents the healthiness of menu items on a 
scale of A (healthiest) to E (least healthy). This score is calculated according to 
the amount of healthy and unhealthy nutrients.  
If the UK government introduced a policy requiring the use of a ‘Nutri-score’ system on food menus, 
how would you feel? (Likert scale ranging from 1 – 5 anchored by “strongly oppose” and “strongly 
support”) 
 
 
 
 
22. [PME measure - participants in both conditions (calorie labels/NS with calorie labels) will be given 
the menu they ordered from]. 
Please look at the menu you were given, and think about the menu.  
 
 “The menu made me concerned about the health effects of consuming less healthy menu items” 
 Strongly disagree 
 Slightly disagree 
 Neither agree nor disagree 
 Slightly agree 
 Strongly agree 
 
“The menu made consuming less healthy items seem unpleasant” 
 Strongly disagree 
 Slightly disagree 
 Neither agree nor disagree 
 Slightly agree 
 Strongly agree 
 
“The menu discouraged me from wanting to consume less healthy items”.  
 Strongly disagree 
 Slightly disagree 
 Neither agree nor disagree 
 Slightly agree 
 Strongly agree 
 
 
 
Strongly 
Oppose 
Oppose 
 
Neutral 
 
Support 
 
Strongly 
Support 

Appendix E: Debriefing text 
In this study we were interested in the effect Nutri-score labels on perceived effectiveness of labels, 
food choice and consumption. Nutri-score labels are used on food packaging in a number of 
European countries.  
In order to categorise items, scores are calculated by considering the 
healthy aspects of an item (e.g.  fibre, protein, fruit, vegetable and nut 
content) and the less healthy aspects (e.g. salt, sugar, fat and saturated 
fat). Scores correspond to a letter where A (dark green) represents the 
healthiest items and E (red) represents the least healthy items. 
Participants were presented with a regular menu, or a menu where all items were given a Nutri-
score categorisation.  
We wanted to investigate whether being shown a menu with Nutri-score would make people rate 
the menu as more effective in terms of communicating the healthiness of items. We also wanted to 
see if being shown the menu made participants more likely to select a healthier option and order 
fewer calories.  
Finally, we wanted to see if being provided with Nutri-score labels was associated with later intake. 
Specifically, if healthier choices are made at lunch time, are these compensated for later in the day 
(e.g. by eating unhealthy food or more food later on).  
The questionnaire about food choice motives and compensatory health beliefs will be used to test 
any characteristics and motivations that may impact the amount of food eaten. 
If this study has raised any issues regarding your weight or eating behaviours, we recommend 
contacting your doctor. 
The following NHS page provides information and guidance on eating a healthy, balanced diet: 
https://www.nhs.uk/live-well/eat-well/ 
Thank you very much for your participation in our study. 
 
 
 
 
 
 
 
 
 
 
 

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