Anorexia
Eating disorders constitute some of the major medical health
problems in the western world. Sufferers share symptoms such as a
distorted view of one’s own body shape and weight, and extreme
disturbances in their eating behaviour, which may present a serious
health threat. Anorexia nervosa, bulimia nervosa and binge-eating are
some of the most common disorders associated with restricted food
intakes or bingeing, as well as distress or excessive concern about
body shape or weight.
We now know that the central nervous system plays a significant role
in the mechanisms behind the abnormal eating behaviour. In a world
surrounded by pressure to be thin, close to 80% of teenage girls start
a diet. Some slip down the dieting slope into anorexia.
Anorexia nervosa is an eating disorder of unknown origin that most
commonly occurs in women and usually has its onset in adolescence. It
affects around 4200 people in NSW alone. Interestingly, before puberty
one in every four sufferers of anorexia is male. After puberty, one in
eleven sufferers is male, though this ratio is on the increase for
males.
Patients with anorexia invariably have a disturbed body image and an
intense fear of weight gain. Anorexia is the third most common chronic
illness in girls and young women (after obesity and asthma) and as many
as one in 200 girls and young women will be affected. The average
duration of the illness is five to seven years. Anorexia has a high
mortality rate (20% eventually die of the consequences of the disease)
and one in five will at least attempt suicide. Sadly, anorexia nervosa
today has no definitive treatment.
One in three young children with anorexia nervosa are boys. After puberty, only one boy has the condition for every nine girls.
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People with eating disorders share symptoms such as a distorted view
of one’s own body shape and weight, and extreme disturbances in their
eating behaviour, which may present a serious health threat. These
include:
- Being afraid of gaining weight
- Feeling fat despite being very thin
- Preoccupation with food, such as obsessive calorie counting
- Rapid weight loss and not wanting to eat
- Maintaing a body weight below ones healthy resting weight
- Obsessive weighing
- Amenorrhea in women - irregular or absent menstrual cycle
- Feeling depressed and irritable
- Denying that anything is wrong
The causes of anorexia are unknown, but the risk factors associated
with eating disorders are becoming clearer. Some of the contributing
factors include:
- Gender – females are at a higher risk, particularly after
puberty
- Genetics – the risk of developing anorexia increases 10-fold if
another family member has developed anorexia
- Personality traits – characteristics such as perfectionism,
negative self- evaluation and food obsessions
- Dieting – dieting is the most common feature and a trigger for the
condition
- Traumatic events – physical, sexual or emotional abuse, bullying at
school, death or illness of a family member can all trigger or
exacerbate the condition
Anyone who is affected by an eating disorder, regardless of its
perceived severity, deserves access to support and treatment. It is
vital to get help sooner rather than later. The longer anorexia is
experienced the more difficult it is to start the recovery process.
At present, a variety of pharmacological treatments are used in
addition to psychotherapy, antidepressants being most common.
Unfortunately, currently available drugs, while helpful, fall far short
of the desired level of effectiveness.
The most effective strategy for anorexia nervosa is multidimensional
treatment that consists of nutritional rehabilitation, medical
attention, individual cognitive psychotherapy, and family counselling
or therapy.
Garvan’s Neuroscience Program is utilising the extensive experience
of our scientists and state-of-the-art technology to study the
significant role of a specific brain peptide system in the regulation
of energy balance and weight control. There is an intricate regulatory
system that governs our appetite and energy intake. Certain proteins
such as neuropeptide Y (NPY) enhance appetite and induce feeding while
others, such as leptin, act as a satiety factor.
Abnormalities in the neuropeptide system have been reported in
people suffering from anorexia nervosa. In addition to disturbances in
the brain, other factors linked to the brain and our responses to food,
such as taste, smell, palatability and visual appearance of food, may
also play a role in eating disorders. Recently, it has been discovered
that NPY also appears in the taste-bud cells, suggesting that this
molecule can exert its effect on appetite both via the brain and the
taste organs. This may represent a neural mechanism that links taste
aversion and eating disorders. The research carried out at Garvan will
investigate the functional contributions of the neuropeptide Y system
in relation to the development and manifestation of anorexia.
Studies have also shown that a gut-derived hormone called peptide YY
(PYY) which promotes satiety in normal subjects is abnormally high in
people with anorexia. Apart from inducing nausea, high PYY levels were
also found to be associated with decreased body weight, body mass index
and bone composition in subjects with anorexia.
In our laboratory, we have also shown that mice with high levels of
PYY have decreased fat and bone mass, suggesting that the loss of body
fat and bone tissue in young people with anorexia may be caused by
these high circulating PYY levels. Our aims are to determine whether
methods to block PYY levels in anorexia subjects may have beneficial
effects in restoring body weight, body composition and food intake.
We hope that eventually our research will lead to new, targeted
medicines for anorexia nervosa and will contribute to greater recovery
rates for sufferers.
News
Great opportunity for Garvan neuroscientist
30 Dec 2005
Dr Deborah Lin, a researcher in the Neuroscience program, has been awarded a full travel bursary to attend a training program at Japan’s prestigious RIKEN Brain Science Institute
Garvan researchers explain how stress makes us sick
05 Dec 2005
Garvan Institute scientists have discovered how a hormone known as neuropeptide Y (NPY) can prevent our immune system functioning properly paving the way for new opportunities for therapeutic intervention.
