Influence of macronutrient-related ambient odours exposure on (congruent) appetite and actual food intake.
Cover story (for information brochure): The influence of hunger and satiety on abilities of logic reasoning

Living in an obesogenic environment, we are surrounded by food odour cues that
trigger these unconscious decisions and induce us to (over)eat. Olfaction plays
an important role in eating behaviour by detecting foods, attracting our
attention, and triggering our appetite. However, the effect of food odours on
subsequent behavioural responses remains unclear.
Olfaction may play a role in appetite and meal initiation. Some studies have
suggested that food odours increases appetite for foods with similar
properties, sensory-specific appetite, and may generalize across foods within
certain categories as taste and energy-density.
On the other hand, contradictory findings have been reported between the
influence of odours on appetite versus actual food choice and intake.
Differences in intensity, type of exposure (explicit or implicit), and
awareness of the odour cue could be responsible for the lack of consistency in
these findings.
Therefore, we propose a series of behavioural studies to extend the knowledge
in the (macronutrient signalling) function of odours and its impact on appetite
and actual food intake. We aim to disentangle the differential effects of
intensity, exposure method (explicit and implicit), and awareness of the cue:
Aware and actively smelling of odours (part A; NL66580.081.18) and unaware
smelling by means of ambient odours (part B).
Results of part A showed that food odours influence SSA but did not affect food
intake. The knowledge learned from part A was used to establish the methods in
the current protocol (part B).

The primary objectives of the current study are to determine the influence of
unaware and passively smelled macronutrient-related odours on appetite, and
actual food intake, in normal weight and unrestrained individuals.
The secondary objectives of the current study are to determine the influence of
unaware and passively smelled macronutrient-related odours on food preferences.
Also, we will determine the correlation between self-reported macronutrient
preference and actual macronutrient intake.

Cover story for participants: The influence of hunger and satiety on abilities
of logic reasoning. Participants will be debriefed at the end of the last test
session.

The current study is a counter-balanced cross-over intervention study.
Subjects will take part in an information meeting and four test sessions. In
each test session, subjects will be exposed to one of the four conditions
(odour representing food high in carbohydrates, protein and fat, and low in
calories) and tested for behavioural measures. In each test session, subjects
will be asked to rate their general and specific appetite and stress, to
perform a computer-based task on food preferences (MTPRT), and some
psychometric tasks (to assess logical reasoning ability; this is done to
distract subjects from the actual goal of the study). Participants will be
provided with lunch to covertly measure ad libitum food intake.

In each test session, participants will be exposed to one of the four
conditions (odour representing food high in carbohydrates, protein and fat, and
low in calories) for a few minutes.

This study is non-therapeutic. The risk associated with participation is
negligible. The burden can be considered as low. The study includes five site
visits in a non-satiated state and an information meeting (approx. total
duration of 5 hours). All odours and food products are considered safe to
use/consume and commercially available. The level of the questionnaires to
measure your ability to reason logically is average to difficult.