Condition category
Nutritional, Metabolic, Endocrine
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Background and study aims
In view of the obesity epidemic, it is important to understand which factors determine the appetizing and/or satiating responses to food cues. It is well known that short exposure to food cues, e.g. the sight or odour of freshly baked bread or pizza, can enhance salivation and appetite feelings. On the other hand, people report to be less hungry after cooking a meal, which is exposure to sight and odour of food for a longer period of time. In this study, we want to investigate some aspects of this apparent paradox. The primary objective is to investigate the effect of exposure to several odours on appetite, appetite for the smelled food and salivation over time.

Who can participate?
Unrestrained healthy women, 18-45 yr old, BMI 18.5 – 25 kg / m2

What does the study involve?
Participants were expected in the lab for 6 times, around lunch time. During every visit, the response to two different test conditions was measured (two test sessions were conducted on one day), resulting in 12 sessions. The first session was a practice session to get the participants acquainted to the procedure. During the remaining 11 session, the participants were exposed to two control sessions with no odour and nine sessions with different odours. During each session, salivation, hunger, appetite, appetite for different kind of foods and food preference was measured. Each session started with baseline measurements in which participants answered the appetite questionnaire and salivation was measured, in a room with no odour present. Subsequently, each participant entered one of the test rooms that contained either one of the odours or no-odour. The participants were given instructions on a computer. The appetite questionnaire was filled out 1, 5 9, 13 and 18 minutes after entering the room and the saliva collected 0.5, 4, 8 and 17 minutes after entering the room. After 20 minutes, the participants entered another room with no odour to complete a food preference questionnaire. When finished, participants received a snack.

What are the possible benefits and risks of participating?
A fee of 90 euros was paid upon completion of the study. Compared to other studies the burden can be considered as low. No possible health benefits.
The risk associated with participation is negligible.

Where is the study run from?
Restaurant of the Future (Netherlands).

When is the study starting and how long is it expected to run for?
The start date was 2 May 2011. The duration of the trial was 8 weeks.

Who is funding the study?
Technology Foundation STW (Stichting Technische Wetenschappen) (Netherlands).

Who is the main contact?
Marielle Ramaekers

Trial website

Contact information



Primary contact

Mrs Marielle Ramaekers


Contact details

Bomenweg 2
6703 HD
+31 (0)317 482520

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

Effect of orthonasal odour exposure time on appetite, appetite for smelled foods and salivation, investigated for different odours: a cross-over study


Study hypothesis

1. One minute exposure to food odours increases appetite, appetite for the smelled food and salivation, compared to baseline (t=0).
2. Twenty minute exposure to food odours increases appetite and salivation, compared to baseline (t=0), but decreases the appetite for smelled foods.
3. Non-food odours evoke different appetite responses than food odours.

Ethics approval

Medical Ethical Testing Committee (METC), Wageningen University, April 2009, ref: NL35493.081.11

Study design

Cross-over study

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use the contact details below to request a patient information




Cross-over study with 8 odour conditions: 5 food odours, 2 odours in duplo (repeated two times), two non-food odours and no-odour (duplo). Each participant completed two sessions per day, in total 12 sessions.

Twenty minute odour exposure to eight different odour conditions: no-odour (duplo), bread odour, chocolate odour (duplo), banana odour, tomato soup odour, meat odour (duplo), grassy odour and pine tree odour. Exposure to one odour during one session.

Intervention type



Not Applicable

Drug names

Primary outcome measure

1. Appetite (on visual analogue scale) was filled out at baseline and 1, 5 9, 13 and 18 minutes after onset of odour exposure
2. Appetite for smelled foods (on visual analogue scale) was filled out at baseline and 1, 5 9, 13 and 18 minutes after onset of odour exposure
3. Appetite for smelled foods measured with food preference questionnaire was filled out 20 minutes after onset of odour exposure

Secondary outcome measures

Salivation at baseline and 0.5, 4, 8 and 17 minutes after onset of odour exposure

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. Women aged 18-45 years
2. Healthy, based on self report
3. Body mass index (BMI) 18.5-25 kg/m2

Participant type


Age group




Target number of participants


Participant exclusion criteria

1. Smoking
2. Restrained eater
3. Lack of appetite
4. Dieting for the past 2 months
5. Change in body weight > 5 kg during last 2 months
6. Vegetarian
7. Hyper sensitivity or allergy to any food product
8. Pregnant or breast feeding during last 6 months

Recruitment start date


Recruitment end date



Countries of recruitment


Trial participating centre

Bomenweg 2
6703 HD

Sponsor information


Technology Foundation STW (Stichting Technische Wetenschappen) (Netherlands)

Sponsor details

Postbus 3021
3502 GA

Sponsor type

Research organisation



Funder type

Research organisation

Funder name

Technology Foundation (STW) (Netherlands)

Alternative name(s)

Funding Body Type

Funding Body Subtype


Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes