THE NEUROBIOLOGY
OF BINGE EATING
Introduction
Various
studies have been carried out to investigate overeating in both clinical and
pre-clinical research. This has been as a result, in part, of the scientific
interest to understand the etiology as well as treatment methods for the
increasing problem of obesity. Rats have been commonly used in the development
of the models of binge eating. According to Avena (2007) palatable diets have
been used in most of the studies in inducing overeating in the animals. The
results of the studies are pertinent to the reported neurobiology of addition.
Nevertheless, it has been noted that non-homeostatic feeding behavior or over-eating
can happen without necessarily causing an increase in body weight or becoming
obese. It is common knowledge that increased body weight or being obese can
have detrimental implications on physiology, neural processes, and behavior. It
is also important to understand the way these factors are impacted by
overeating behavior (Rebecca et al. 2011).
Animal
models of binge eating
One
of the animals models used in explaining binge eating is the sugar addiction
model. A study carried out in 1987 study revealed that sugar operated as a kind
of analgesic drug. Morphine blocker was found to work positively in blocking
the effects of the drug. Just like drug addition, it was revealed in the study
that animals can become addicted to sugar (Hagan, et al. 2002). DesMaisons (1998)
highlighted that idea of sugar addiction as a quantifiable physiological state.
She suggested that this state was as a result of opioid receptors activation.
The hypothesis of her model was that sugar addiction fell in the same DSM IV for
other drug abuse.
In
2002, fifteen years after the model was suggested, a study carried out at Princeton
started revealing the neurochemical implications of sugar. The study suggested
that as a result, sugar could play the role of a gateway drug. In the study,
chow was fed to rats, together with a 25 percent solution of sugar the same
concentration as available in soft drinks. The results of the study were
collected one month later (Deroche-Gamonet, Belin and Piazza, 2004). It was
revealed that the rats had become addicted to the solution; they were also
revealed to eat less chow and had an increased intake of the sugary drink to
200 percent. It is asserted by the sugar firms that the same kinds of effects
are evident in animals consuming drinks which tasted sweet, even if they did
not have any calories. Nevertheless, it is suggested by some researchers that
the caloric value may not have any impact. It is sugar as well as the taste of
sweetness that cause brain stimulation through activation of endorphin receptor
regions. These are the same chemicals which use of morphine and heroine
activate in the brain (Rebecca et al. 2011).
According
to Hagan, et al. (2002) another study carried out in 2008, revealed that sugar
has effects on dopamine and opioids in the brain. This means that there is the
possibility of having addictive possibility. The study referred to bingeing, craving
withdrawal, and cross-sensitization, and provided each of the factors with
operational definitions demonstrating that bingeing of sugar acts as a
reinforcer. The behaviors are suggested to be associated with neurochemical
alterations occurring in the brain when one is addicted to drugs.
Research
has developed methods of diagnosing food addiction with the application of the
model. To establish the guidelines for identification of addicted individuals,
such methods or scales as the Yale Food Addiction Scale, have been created. This
tool is the initial psychometrically validated method for the establishment of
the criteria for food addiction, on the basis of DSM-IV criteria for substance
abuse modification. Together with the development of definite identifying
behavioral method, studies of genetics and the brain have supported the idea
that food addiction is as possible as drug addiction and can be easily diagnosed
using the same methods used in the diagnosis of drug addiction (Volkow and Li, 2004).
One
of the main strengths of the model is that it is the very first model that has
established an inclusive set of criteria related to addiction when rats are fed
with palatable food (Deroche-Gamonet, Belin and Piazza, 2004). This means that
the model presents an effective mechanism in the study of mechanisms of the
brain related to regular binge-like bouts. The model has the potential of
helping with the creation of pharmacotherapies with the aim of suppressing bingeing
or possible food addiction. These kinds of treatments might be important in
those persons with binge eating disorders comorbid substance use. Avena (2007) posits
that an additional strength of the model is that, given the fact that the
bingeing animals do not necessarily become obese or overweight; it is possible
to separate the behavioral factor of binge-type eating. This is particularly
important given that the implications of overweight or obesity can cause
alterations in the brain which has an impact on reward. This means that by
separating the factor of binge-type and the results of overweight, it is
possible to determine the impact of bingeing palatable food.
Other
studies have revealed opposing results that have suggested indications of
addiction when utilizing other alternating sucrose access programs. Irregular
access to sucrose cross-sensitizes with a drug such as cocaine. There is thus,
facilitated sensitizing of the DA agonist quinpirole. Additionally, in the
animals, anxiety-like behaviors have been revealed where there is restricted
availability of diet high in sucrose. Some studies have also noted some
behavioral and physiological alterations that propose a negative state in
animals which consume sugar sporadically. For example, the withdrawal of sugar
has been shown to lower the temperature of the body as well as instigating some
indications of aggressive behavior (Berridge, 2009).
The
neural changes that are observed in binge eating
According
to Berridge (2009) various neural changes entail needing a reward, enjoying it
and creating predictions from cues. These chances are experienced regardless of
whether the reward is a drug or a food. Enjoyment
of the reward and wanting the food or drug rewards are behaviors having neural
impacts. The neural chances that occur
in bingeing are such changes as in opioid and dopamine receptor binding, acetylcholine
and dopamine releasing in the nucleus accumbens, and enkephalin mRNA expression
(Szczypka, Rainey and Palmiter, 2000).
There is a small part in the nucleus accumbens shell that with the use of
endocannabinoid and opioid transmission regulates the craving responses to
sweet foods. An important role is played by the ventral pallidum in enjoying
the sweet food, as a blocking or abrasion of γ-aminobutyric acid transmission
in the part of the brain eliminating liking responses. Alternatively, in the
reflexive, wanting is a non-cognitive feeling that depends on the transmission
of dopamine from the ventral tegmental part. The chemical is transited to the
nucleus accumben, the process also involves the hypothalamus and the amygdale.
The main point in this case is that transmission of the chemical tends to be
associated with the wanting of the food, and not enjoying or knowledge of the
rewards. The release of the chemical can be triggered simply by learning about
the cues, such as smell (Volkow and Li,
2004).
The
neural changes that accompany binge-eating are similar to those seen following
drug use. The neural changes that accompany binge eating are so similar to
those that are evident in the use of drugs. This is because the neural changes
work on the idea of reward seeking, whether from the food or drug. The changes
start with a behavior that is consciously motivated as a result of expecting a
reward. Various neurotransmitters, such
as including γ-aminobutyric acid), dopamine, glutamate, serotonin,
acetylcholine and endogenous opioid peptides have been suggested to play a part
in the addiction to drugs. Among them, dopamine has been showed to play a major
role in the reinforcement of the use of drugs. This has emerged as the case
with addition to food. Abuse of drugs or food has been reveled to increase
concentrations of the chemical. Particularly, it is evident that the
reinforcing impact of drugs or food is caused by the incapacity to exceed the level
and period of the rapid increases in dopamine happening when triggered by the
reinforcers. The neural effects are the same for drugs and food, only that
different foods and drugs triggers the changes differently (Berridge, 2009).
Experiment
In
the experiment, rats are maintained 12-hour food deprivation daily. This is
followed by access of 12 hours daily to a 25 percent glucose and chow. There is
also a control group that is fed on sugar ad libitum. The results of the
experiment are that in a few days, the rats start to increase their consumption
of the sweet solution and less consumption of chow. The feeding pattern of the
rats completely changes such that they consume larger amounts of sugary
solution during the access period. When the solution is withdrawn, there are
signs of efforts by the sugar bingeing rats to access the solution. This shows
that there is an effect of bingeing on the neurology of the rats that is out of
their control. In the study, bingeing has been found to release the neurotransmitter
dopamine in the brain (Rebecca et al. 2011).
Similar
results are revealed in the form of strong cravings of sweet food on
individuals who binge. This is because of the release of dopamine which sends
an internal message for them to consume sugary foods even when they are aware
of the negative effects. It is only when they consume sugar that they feel
satisfied. Just like with the rats, when the sugar is withdrawn the individuals
who binge become anxious (Smith and Schneider, 1988).
The animal model of
binge eating
The
sugar addiction model, already described earlier in the discussion will be used
in explaining sugar addiction on the subjects of the experiment. The model
shows that exposure to sugary food or solutions cause addiction on the subjects
in the same way drugs do. The model has been used in the interest to understand
why addiction to sugar happens in animals exposed to sugary solutions (Smith
and Schneider, 1988).
Testing
Studies
of the brain on regions such as the medial orbitofrontal cortex, the anterior
cingulate cortex and the amygdale have been used in testing whether they are
responsible for individual’s failure to control their consumption of food. This
is because these are the parts of the brain that are activated by the use of
palatable food. Testing of these parts of the brain with the use of mechanisms
such as Scores on the Yale Food Addiction Scale can reveal whether they have a
role to play in the craving of some food, similar to craving for drugs. Brain
scans can also be used in testing these parts of the brain to come up with
conclusive evidence. This is because these changes are more related to binge
eating than they are related to increased body weight. This only means that
increased body weight cannot be used as a conclusive indicator for food
addiction (Smith and Schneider, 1988).
The treatment of binge eating
The
results of the experiment can be used to positively inform the treatment for
binge eating. Binge eating has been found to increase the release of dopamine
in the brain the same way as addictive drugs. This leads to food addiction or
binge eating (Szczypka, Rainey and
Palmiter, 2000). This means that with the increase in the release of
dopamine, individuals will continue to binge. Withdrawal symptoms are noted in
the withdrawal of the food. The results suggest a close association between the
levels of dopamine and the urge to eat sugary food. This means that a change in
the consumption behavior for people who are already bingeing lies in the
changes in the dopamine levels. Regulating the release of the chemical can play
a major role in the treatment of bingeing according to the results of the
experiment. Research suggests that regulation of the neural chemicals can play
a major role in the controlling of bingeing Berner et al. (2011).
Conclusion
Neurological
and behavioral research has provided evidence of a similarity between addiction
to food and addiction to other drugs.
The similarity has been found stronger in the case of craving for food
or drugs. This has led to the lack of control over the craving for eating or
using drugs. Research has revealed that the main reason for the inability to
control the craving lies in the release of chemicals in the brain such as
dopamine. Treatment for bingeing lies in the ability to control the release of
these chemicals. A very interesting direction in the research on binge eating
is the determination of whether individuals can train to control their craving
for the food. If this is possible, it would be an important milestone in the
control of obesity and related disorders. The results of such research would
also inform health care providers and therapists on advising people to work on
their craving.
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