Recovery and Reinstatement
Kristen Hurley
Saint Anselm College
KHurley@anselm.edu
Additional Information
Kristen Hurley
Saint Anselm College
KHurley@anselm.edu
Additional Information
|
|
|
|
|
|
|
|
Activity-based anorexia is a dangerous disorder that occurs mostly in young females. This study attempts to answer the question of whether activity-based anorexia occurs faster, slower, or at the same pace in a reinstated trial compared to the initial trial. The subjects included six female Sprague Dowley rats, three of which were six months old and three of which were a year old. All of the rats were housed in Whymann Running Wheels with passages controlled by a sliding door. To find significant differences between and within the groups in the initial and reinstated trials, independent and dependent t- tests were used. It was found that weight loss actually occurs slower in the reinstated trial, which was opposite of what was predicted. However, the rats ran for longer distances in the reinstated trial. These finding can be used as a starting point for further research on activity-based anorexia and the effects of relapse.
Activity-based anorexia can be studied in rats in
order to gain a better understanding of the parallel between physical
activity
and anorexia in humans. In modern Western culture thinness and
activity
are valued, especially for women. Today thinness is a sign of
beauty,
but unfortunately, some people would go to any length to obtain the
“perfect
body,” which is often a body that is too thin. If a person
obsesses about his or her body image and takes steps to reduce food
intake
and increase exercise, anorexia could result. Anorexia, the
self-starvation
eating disorder, can lead to health problems and even death. It
has
been noted that anorexics tend to be restless and have a higher level
of
hyperactivity than those who are not anorexic (Crisp, 1972).
Excessive
exercise is associated with a higher risk of an eating disorder (Epling
& Pierce, 1983). In an attempt to gain a better
understanding
of why this phenomenon occurs, activity- based anorexia can be induced
in rats in an attempt to model how activity and anorexia are related,
and
apply this knowledge to humans.
Activity-based anorexia can be induced in
rats when placed under several conditions. If rats are placed on
a restricted feeding schedule and are allowed access to a running
wheel,
the rats will begin to consume less food and exercise excessively until
the point of starvation. It has been shown that increased
physical
activity interferes with food ingestion in rats (Epling & Pierce,
1991).
In other words, when rats are allowed access to a running wheel, they
will
actually ingest less food than a control condition where rats do not
have
access to a running wheel (Dwyer & Boaks, 1997). The reason
for
the phenomenon of consuming less food while increasing exercise can be
explored by examining several studies. In a study by Boakes and
Dwyer
(1997), weight loss in rats produced by failure to adapt to a
restricted
feeding schedule was investigated. Boakes and Dwyer hypothesized
that rats that run excessively may fail to adapt to a restricted
feeding
schedule. In the study, rats were exposed to a running wheel for
two hours prior to a one and a half hour food access. The cycle
caused
a decrease in food intake, increase in running, and a drop in body
weight.
There was a delay before weight recovery began. It was observed
that
young rats with a low initial body weight predicted a greater chance of
activity-based anorexia. The experiment concluded that
activity-based
anorexia is related to a failure to adapt to a new feeding schedule,
which
is consistent with Boakes and Dwyer’s original hypothesis.
Hebebrand et al. (2003) compared hyperactivity in
patients with anorexia nervosa and in semi starved rats. It has
been
observed that mice treated with leptin will decrease body weight and
increase
spontaneous activity levels. Therefore, leptin may play a direct
role in increased activity. In mice, a decreased level of serum
leptin
was observed as a response to food deprivation. Leptin treatments
have a reversing effect on hormonal responses to food
deprivation.
However, the effects of leptin on a free feeding paradigm have shown to
have minor effects on hormonal responses. Therefore, it can be
concluded
that leptin may act as a starvation signal. Rats that are food
deprived
and exposed to running wheels may have decreased levels of serum
leptin,
enforcing the role of leptin as a signal of starvation.
Therefore,
leptin can represent a signal that triggers hyperactivity. The
study
contained two groups, one experimental group in which the rats received
leptin and one control group where no leptin was administered.
The
lighting consisted of twelve hours of light and twelve hours of
darkness.
Rats that were given leptin with a free feeding schedule remained
active
during the dark period. During the food restriction phase, the
rats
were given food one hour before the dark cycle. In the control
rats,
a significant increase of anticipatory behavior was noted that was
associated
with feeding time, which was diminished as a result of leptin
infusion.
When in the dark period, the activity level of the rats was also
diminished
as a result of the leptin infusion. The suppressive effects of
the
leptin can be observed in both the dark and light conditions. The
leptin-treated animals showed reduced semi-starvation induced
hyperactivity.
However, the decrease in body weight was the equivalent to those in the
control group. The reason for this equivalency between the
experimental
and control groups may have to do with the tachymetabolic effect of
leptin
in food-restricted rats. In food restricted mice, the metabolic
rate
becomes elevated to its normal level as a result of the leptin
injections;
however the leptin had no effect under the free feeding paradigm
(Hebebrand
et al., 2003).
Rats with semi-starvation induced
hyperactivity
have similar parallels to symptoms of anorexia nervosa seen in
humans.
Such symptoms include food restriction, weight loss, and
hyperactivity.
However, caution must be used when generalizing semi-starvation induced
hyperactivity from rats to humans. Humans with anorexia nervosa
may
experience drive for thinness weight phobia, and other
psychopathological
features that animals do not experience. Therefore, research on
this
topic can be extremely helpful to gain a better understanding for the
biological
aspects of semi-starvation induced hyperactivity but caution must be
used
when generalizing findings to humans because of the psychological
features
that occur in anorexia nervosa patients (Hebebrand, et al., 2003).
Several studies have focused on various
aspects
of activity based anorexia in rats including the injection of
benzodiazepines,
effects of food anticipatory behavior, and a variety of other
studies.
It is important to observe the rate at which rats recover from activity
induced anorexia and how quickly body mass decreases in a reinstatement
as compared to the first trial. These findings may help
researchers
gain a better understanding of how recovery and relapse into an
anorexic
state can have an effect in humans. Many anorexics successfully
recover
from the disease but relapse can occur at any time during
recovery.
It is important to understand what relapse in anorexia entails.
Since
relapse is a prevalent possibility in individuals suffering with
anorexia,
it would be extremely helpful to understand the nature of how relapse
compares
to the initial anorexic state. In learning more about initial
relapses,
hopefully future relapses can be prevented. In this study, rats
will
be given access to a running wheel and will be placed on a restricted
feeding
schedule. The rats will be weighed once a day and will remain on
the restricted feeding schedule for a ten day period. If the rat
loses thirty percent of its body weight before the ten days are
finished,
the rat will be removed from the study. After ten days the rats
will
be taken off the restricted feeding schedule and allowed to gain back
their
original body weight. The rats will then be reinstated into the
activity
induced anorexic condition for ten days. The rate at which the
body
mass decreases will be compared to the original condition. This
process
will be conducted twice in an attempt to determine if body weight is
lost
faster in a reinstated trial.
Subjects
The subjects in this experiment consisted of six
female Sprague Dowley rats. Three of the rats were one year old
and
the remaining three rats were six months old. All of the rats
were
obtained from the psychology department, which obtained the rats from
Harlan
Breeders in Indianapolis. The rats were housed individually in
separate
cages. All rats were allowed scheduled feedings of one hour per
day
and access to water at all times. The rats were weighed at 8:15
am
each morning. The lighting schedule consisted of twelve hours of
light and twelve hours of darkness.
Apparatus
Six Whymann Running Wheels with odometers were
used
to house each rat. The running wheels were connected to home
cages
with passages controlled by sliding doors. Each of the rats was
weighed
individually on a standard scale, each morning. Water was
provided
in bottles for each rat at all times. The rats were kept at room
temperature in the laboratory at all times. Access to the
laboratory
was limited strictly to weighing and feedings to avoid interference
with
activity.
Procedure
Six rats were placed in cages with a running wheel attachment. The rats had access to the running wheels at all times, except during a one hour duration feeding time. On day one of the experiment, the rats were weighed in order to obtain an initial body weight. The rats were then placed in their individual cages and given ad lib access to food in order to obtain baseline data. On successive days, the rats were restricted to a one hour feeding period, from 8:15am until 9:15am. The morning feedings of one hour continued for ten days. If a rat lost thirty percent of its initial body weight or more, the rat was removed from the study. After ten days the rats were placed into cages with no running wheels. The rats were fed and allowed to gain their original body weights back. When the rats obtained their original body weights, they were placed into the cages with the attached running wheels. The rats were weighed and placed on the same restricted feeding schedule as the initial trial. In this second procedure, the exact same procedure as the initial procedure was used. Originally, the rats were supposed to be housed in the cages with the attached running wheel until each rat lost thirty percent of its original body weight. However, due to a time restriction, the rats were not allowed to reach criterion. Therefore, the rats were compared based on ten day time spans. The rats were housed in the cages with the attached running wheel for ten days in the initial trial and the reinstated. The data was based on the comparison between the initial ten days and the reinstated ten days instead of a thirty percent weight loss criterion. One of the younger rats in the initial trial lost just under thirty percent of its original body weight at the end of the tenth day. However, because the rat exercised excessively, the rat died.
The hypothesis stated that the rats would lose
more
weight and lose it faster in the reinstatement of the experiment.
However, both t-tests indicated that there was no difference between or
within the two groups or the two trials in the amount of weight that
was
lost. Also, both t-tests indicated that there was no difference
between
the two groups or the two trials in the amount of food consumed.
Although the results for the number of revolutions between subjects
were
not significant, the results for the number of revolutions within
subjects
were significant. This means that the rats ran a significantly
greater
distance in the reinstated trial compared to themselves in how far they
ran in the first trial.
Although few significant differences were found
between the groups, some of the differences in the groups results
would have been more accurate with a larger sample size. Some of
the results were close to being significant, for example, the number of
revolutions measured by an independent t-test equaled .074.
Perhaps
with a larger sample size this difference would have proved to be
significant.
This study only contained two young rats and three older rats.
The
research presented can be used as a starting point in later research
with
a larger sample size to obtain more accurate results.
The results of this study indicate that activity
based anorexia in female rats actually does not significantly occur
faster
in a reinstated trial. However, the rats did run significantly
more
revolutions in the second trial. The reason the rats did not lose
weight faster the second time may have to do with the fact that the
rats
consumed more food in the reinstated trail. Although the
difference
in food intake in the reinstatement compared to the first trial did not
reach statistical significance, the small sample size may have been a
factor.
Therefore, if there were more subjects in the population, food intake
in
the reinstatement may have shown a significant increase.
One possible confounding variable in this study
may be the fact that one of the younger rats had died of activity based
anorexia in the first trial. The data for this rat could not be
included
in the reinstatement phase. Therefore, the population was even
smaller
than at the start of the study. The rat which was lost in the
first
trail had lost just under thirty-percent of its original body weight
and
ran almost three and a half miles in a twenty four hour period.
This
amount of running was extraordinary compared to that of the rest of the
rats in the sample.
Crisp, A.H. (1965). Primary anorexia nervosa or weight phobia in the male: Report on 13 cases. British Medical Journal,
Additional Information
Saint Anselm
College Department of Psychology
About Journal of
Experimental
Psychology- Animal Behavior Processes
Animal Learning and Behavior.
APA Journals
KHurley@anselm.edu