The present study aims to investigate whether energy intake is reduced when participants consume a reduced portion size (15% compared to the 'control' portion), and also to see whether awareness of this reduction affects energy intake.

In the present study, all participants will participate in two sessions - the baseline session and the experimental session. In the baseline session, participants will be given ad libitum access to a lunch meal (followed by ad libitum access to dessert), and ad libitum access to a dinner meal (followed by ad libitum access to dessert). Then, after a washout period of between 1-6 weeks, participants will return to complete the experimental session, where they will be randomised to one of three conditions:

Condition 1 (control condition): The same as the baseline condition except that the lunch will be of a fixed portion which participants must consume all of - this portion size will be the same amount of food as was consumed in the ad libitum lunch meal in the baseline session (participants will be told that the amount of food served is the same as the amount they consumed in the baseline session).

Condition 2 (reduced aware condition): The same as the baseline condition except that the lunch will be of a fixed portion which participants must consume all of - this portion size will be 15% less than the amount of food consumed in the ad libitum lunch meal in the baseline session (participants will be told that the amount of food served has been reduced from the amount they consumed in the baseline session).

Condition 3 (reduced unaware condition): The same as the baseline condition except that the lunch will be of a fixed portion which participants must consume all of - this portion size will be 15% less than the amount of food consumed in the ad libitum lunch meal in the baseline session (participants will be told that the amount of food served is the same as the amount they consumed in the baseline session).

Inclusion Criteria:

• United Kingdom (UK) residents able to visit laboratory on campus in Liverpool, aged ≥ 18
• Body Mass Index (BMI) between 18.5 and 32.5 kg/m2
• Proficiency in English language
• Self-report willingness to eat each of the test foods

Exclusion Criteria:

• Current medication use which affects appetite
• Pregnant
• Currently or previously diagnosed with an eating disorder
• Currently on a diet
• Have any food allergies or intolerances
• Are vegan

An anonymised data set will be published on the open science framework for anyone to access.

Data will be available after data collection has finished, this will be available indefinitely.