The effects of mastication and sweetness on cephalic phase responses

Obesity is one of the world*s major health problems and the number of obese
people in the western society continues to increase. 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
can be consumed at a fast rate. Quick eating and binge eating have an enormous
effect on body weight as it often leads to overconsumption.
The ability of the human body to regulate food intake plays a key role in the
prevention of overconsumption. Although feeding is necessary for survival it is
also a great challenge for the body to maintain homeostasis through metabolic
adaptations, which has been referred to as the paradox of feeding.
Intake regulation starts with the oral processing of food. During the chewing
process nutrients, odour and taste molecules are released from the food matrix
in the mouth, increasing oro-sensory exposure which stimulates the cephalic
phase response (CPR). 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 before
swallowing food.
The function of CPR is to prepare the body for incoming food and subsequently
digestion. The cephalic signals consequently help to induce satiation. A Lack
of, or diminished cephalic phase 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.
Mastication and oro-sensory exposure help to regulate food intake by inducing
the cephalic phase response consequently inducing satiation. Mastication
induces satiation through several mechanisms; a direct effect (shown in
rodents) through histaminergic activation of the hypothalamus and
paraventricular nucleus, by stimulating the cephalic phase responses through
increased effort and increased oral processing time duration and the
consequently slower ingestion rate and mere contribution to sensory specific
satiety. Besides the duration of the oro-sensory exposure as determined through
the mastication process the cephalic phase response could also be enhanced
through the intensity of the stimuli (i.e. taste) by for example changing the
sweetness of a food product.
Taken together; quick food consumption seems to play an important role in
weight balance. However, it is not known whether the chewing movements or the
sensation of (sweet) taste is most important in inducing the cephalic
responses. Therefore the main objective of this study is to determine the
effects of mastication duration and oro-sensory stimulation intensity
(sweetness) on the endocrine and metabolic cephalic phase hormonal responses.
This knowledge may be used to develop products or strategies that enhance
healthy choices and eating behaviour.

Primary aim: To determine the effects of oro-sensory exposure stimulation
through mastication duration and sweetness intensity on the endocrine and
metabolic cephalic phase responses.
Secundary aim: To determine whether the magnitude of cephalic phase responses
affects subsequent satiation.

The study has a randomized cross-over (2x2) study design with a control
condition; all participants (n=22) receive each treatment and are their own
control (within subject effects). Participants join an information meeting
during which they sign conformed consent if willing to participate, after that
participants fill in a questionnaire about the in- and exclusion criteria of
the study and taste the model foods. If eligible, participants come to the
modified sham feed training, after the training participants should be able to
have a recovery rate of at least 85% in order to pass the second screening. If
the participants is found to be eligible according to all study criteria he/she
participates in 5 test sessions during which the participant sham feeds either
a sweet or non-sweet chewy or non-chewy strawberry *gel like* model food.
During the control condition participants do not sham feed. Immediately after
the sham feed session participants are offered an ad libitum lunch.

At the day of the test sessions, a canulla is inserted after which the
participant has to feel " good" (this will be asked to the participant) for at
least 30 minutes. After that the sham feed experiment will start. Participants
will be asked to sham feed on one type of model food and will be instructed
when to eat a new gel and when to spit out. Participants will chew
approximately 30 gels of 5 gram in +/- 15 minutes. During the sham feed period
9 blood drawings will be taken and participants are asked to fill in appetite
questionnaires.
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 (22).
All subjects will eat all four types of model foods in a randomized order, one
type per session.
After the sham feeding experiment participants will be invited to the lunch
room where they will receive a glass of water and buns with cheese, ham,
hazelnut pasta, or strawberry jam from which they can eat until pleasantly
full. After the ad libitum breakfast/lunch participants will again be asked to
fill in an appetite questionnaire.

The intervention is non-therapeutic to the subjects. The risk associated with
participation is negligible and the burden can be considered as moderate.
During five morning sessions participants will sham feed on model foods which
is a common technique used in sensory research to study the cephalic phase
response. Ingredients used to make the model foods in this study are commercial
available or are present in commercially sold food products and are approved by
the FAO. Blood samples are taken by a qualified research nurse.Sometimes a
hematoma, feelings of dizziness, nausea or fainting due to fasting can occur,
but the risks of these events are minimal. If during the screening glucose
concentrations outside of the normal range are detected, subjects will be
notified by the research nurse and redirected to a general practitioner.
Permission for this will also be asked in the IC. Subjects who do not agree
with this requisite are excluded from participation in this study. 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 and consequently help prevent overweight and
obesity. In conclusion, we consider the knowledge obtained and possible
implications of this study to outweigh the small individual burden.