The effects of mastication and oro-sensory exposure on satiation

Despite the progressed insights in the causes of the obesity problem, much
remains unknown while the number of obese people in the western society
continues to increase. Many factors have been identified that contribute to the
problem. One of the major contributors to obesity is the obesogenic food
environment that is characterised by large portion sizes of palatable, high
energy dense foods that are relatively inexpensive, making it possible for
susceptible individuals to overconsume.However, despite this tempting food
environment there are individuals that do not seem to overconsume and are able
to maintain a healthy body weight.
The ability of the human body to regulate food intake plays a key role in the
prevention of overconsumption. Oro-sensory exposure to food and mastication
help to regulate food intake. One of the theories is that these factors
regulate intake by inducing and stimulating the cephalic phase response. The
cephalic phase response is the first phase of digestion, including all
physiological, endocrine and autonomic responses stimulated by sensory cues
such as taste, smell and the sight of food. A Lack of, or diminished cephalic
phase response induced by modified sham feeding or as a result of quick food
consumption has been shown to disrupt the digestive system. Processes affected
are metabolism systems such as the insulin and blood glucose regulation and
lipolysis together with the reward and satiety systems. In both animal and
human studies it has been shown that this disruption of the digestive system is
related to decreased appetite responses and weight gain.
In line with this, studies have found that a decreased oro-sensory stimulation
due to a fast ingestion rate and little chewing effortare associated with
obesity. Ingestion rate determines the size of the meal, as faster consumption
leads to a higher intake. For example, liquids are consumed much faster
compared to solid- or semisolid foods and therefore ad libitum intakes are
found to be higher, even when energy density was kept equal. This confirms the
adverse effects of foods that can be eaten in a fast rate without (chew) effort
as they induce a shorter orosensory exposure per food unit, resulting in a
delayed or decreased satiation response and consequently higher food intake.
This suggests that proper (oro-) sensory stimulation and the enhancement of the
cephalic phase response may play an important role in the prevention of the
obesity problem.
Individuals not affected by the obesogenic food environment may feature
distinctive eating behaviour that stimulates the cephalic phase response
causing them to refrain from overconsumption through fast increased satiation
feelings.
The way food is processed in the mouth when first ingested is one of the
characteristics of eating behaviour. Oral processing includes the mastication
motility and secretory contributions and has as a primary function to breakdown
food in the mouth. Mastication motility affects the oro-sensory stimulation and
perception and is dependent of the food properties such as texture and flavour.

Chewing behaviour is consistent within individuals but varies widely between
subjects. Typical chewing patterns in adults are developed in early childhood
with only some minor adaptations due to positioning of permanent teeth and
tooth loss. Four main eating behaviour patterns have been described in
literature; chewers, crunchers, smooshers and the suckers. Chewers and
crunchers are characterised by their preference to break down food with their
teeth. Crunchers are distinct from chewers as they prefer foods for which more
force is needed to breaking down the food, chewers on the other hand prefer a
long chewing time. Smooshers and suckers prefer to manipulate foods with use of
their tongue and palate. The main difference between these two eating types is
mouth behaviour and the preference for hard foods (lolly pops) by the suckers
and soft foods (pudding) by the smooshers. Although a person may be classified
in one of these eating behaviour types based on his or her preferences they may
still show other eating styles upon eating certain products.
How food is processed in the mouth determines the sensations that are perceived
when eating the food. However, the manner of food processing is also dependent
of the food eaten, for example, a study of Wijk et al. found that oral
processing time and oral movements increases when increasing the sweetness of a
semi-solid food. It has been suggested that the balance between efficiency and
perception determines the individuals eating behaviour or oral processing style
and that this is dependent of the food and its pleasantness. Meaning that
individuals chew food in such a way that it provides the, for them, optimum
flavour and flavour intensity.
Mastication and orosensory exposure are therefore closely related but the
respective roles of both factors in their effect on satiation are unknown.
Therefore the main objective of this study is to determine the independent and
combined effects of mastication duration and oro-sensory stimulation intensity
on satiation (ad libitum intake). The second objective is to investigate
whether chewing behaviour type affects satiation through orosensory exposure
time.

Primary Objective: To determine the independent and combined effects of
mastication duration and orosensory stimulation intensity on satiation.

Secondary Objective: To investigate whether chewing behaviour type affects
satiation through orosensory exposure time.

Primary study hypothesis:
When magnitude of the oro-sensory stimulation intensity and mastication are
increased this will lead to an equal and additive reduction on food intake.

Secondary study hypothesis: People with chewing and crunching eating styles
have shorter orosensory exposure time compared to smooshers and suckers and
consequently will have greater reduction of the ad libitum intake when
mastication and orosensory factors are increased.

The study has a randomized cross-over (2x2) study design; all participants
receive each treatment and are their own control (within subject effects). The
duration of the study will be approximately 3-6 months (depending on the
recruitment) and will take place in the sensory lab of Wageningen University.

Information meeting and first part screening:

Once the study is explained to the participants and when willing to participate
the participants sign informed consent. After that, participants take part in
the first part of the screening where they will be asked to fill in the Dutch
Eating Behaviour Questionnaire and texture preference questions together with
questions about the in- and exclusion criteria questions. When subjects fulfil
all in- and exclusion criteria they will be invited for the second part of the
screening.

Second part screening:
During the second part of the screening participants will be asked to answer
general questions about the model food including the liking. Subjects will only
join the four test sessions when they score at least once (out of two) a 5 on a
nine point hedonic scale for both model food structures (chewy and not chewy).
The model foods have a gel-like structure similar to pudding or panna cotta.
The four types will differ either in structure (chewy vs. not chewy) or
perceived sweetness (low and high intensity) in a 2x2 design:
Model food 1: Chewing duration Long, sweetness Intensity High (CLIH)
Model food 2: Chewing duration Short, sweetness Intensity Low (CSIL)
Model food 3: Chewing duration Long, sweetness Intensity Low (CLIL)
Model food 4: Chewing duration Short, sweetness Intensity High (CSIH)

During the second part of the screening subjects will also be asked to rate
liking for the sweetness of 6 gels with different sweetness levels, on a line
scale (100 mm visual analogue scale VAS). Based on this, two individual based
sweetness levels will be chosen in such way that palatability for both
sweetness levels is equal. Meaning that 2 sweetness intensities for each
subject will be chosen, one that is *just not sweet enough* and one that is
*just too sweet*. Furthermore, weight and height will be measured to calculate
their daily energy need (based on the Schofield formula) and food neophobia
level will be determined based on a questionnaire.

Test sessions:
When sweetness levels and overall liking of the model foods is determined, and
participants fulfill al in- and exclusion criteria four sessions will be
scheduled.
The evening before each session participants will be asked not to do intensive
exercise (walking and biking is allowed). Before each session participants will
be asked to refrain from eating and drinking (besides water) 4 hours before the
measurement.
Before the start of the test session participants will be given pieces of bread
with light butter (halvarine) and cheese and one glass of water (150 ml) for
them to eat to standardize thirst and hunger/satiation feelings. The amount of
bread given will be determined based on the average energy need calculated by
the age, weight and height of the participant.
During the sessions subjects will be asked to eat one of the four types of
model foods until comfortably full (ad libitum intake). All subjects will eat
all four types of model foods in a randomized order, one type per session.
During the ad libitum intake video recordings will be made. Markers (stickers)
will be placed on the chin and nose of the participant to measure chin
movement. Based on the movements of the chin chewing behaviour will be
determined. Furthermore they will be asked to rate some model food -specific
and appetite related questions.

During the last test session participants will be asked to fill in the eating
behavior type questionnaire to determine whether they are 'chewers, crunchers,
smooshers or suckers'.

The risk associated with participation is negligible and compared to other
studies the burden can be considered as low. Performing sensory tests and ad
libitum intake experiments is considered to be a low burden for participants.
Participating in the study takes 6 hours per participant and only the 4 hours
refraining from eating can be considered a small burden but is considered to be
standard practice in sensory research. With this study we would like to
determine how mastication and oro-sensory exposure are contributing to the
regulation of food intake as they are closely related. This knowledge may be
used to develop products or strategies that enhance healthy choices and eating
behaviour. In conclusion, we consider the knowledge obtained and possible
implications of this study to outweigh the small individual burden.