NEDA TOOLKIT for Parents
Appetite For people with eating disorders, the decision of what
to eat is a complicated snarl of anxiety and guilt. And
it’s not much less complicated for people without
eating disorders. Our appetites — for what and how
much we eat — are regulated by a complex array of
hormones, hunger, and desire. When these systems
are working properly, everything is great. We eat
what we need and want, more or less. Our weight is
appropriate for our genes and body type. Our diet is
varied and tasty.
As in any complex system, however, things can go
wrong. Research has shown us that eating disorder
sufferers have problems regulating feelings of hunger
and satiety that can perpetuate and perhaps even
contribute to the onset of illness. Scientists have
identified several key hormones and brain processes
that may be malfunctioning in people with eating
disorders. Leptin and ghrelin, discussed below, also
interact with a variety of other hunger and satiety
signals to help keep our bodies fueled properly.
Leptin is a hormone produced by fat cells that
signals satiety. Researchers at Rockefeller University
discovered the leptin gene almost 20 years ago (Zhang
et al., 1994), and researchers soon showed that leptin
is one of the (many) reasons why diets don’t work. As
body fat stores go down, so do leptin levels. Lower
leptin levels mean that it takes longer to feel full after
eating, which serves to bring the body back to its
original weight.
Since leptin is a key component of appetite and body
weight regulation, scientists suspected that leptin
might be involved in eating disorders. Researchers
measured leptin levels in 67 women with eating
disorders (21 had anorexia, 32 had bulimia, and 14 had
binge eating disorder), and compared this to 25 healthy
women (Monteleone et al., 2000). As expected, leptin
levels were significantly elevated in the women with
binge eating disorder compared to healthy women, but
they were significantly lowered in women with anorexia
or bulimia.
Normally, high levels of leptin are associated with
lower levels of endocannabinoids, brain chemicals
that, among other things, regulate appetite (DiMarzo
et al., 2001). Low levels of endocannabinoids should
make a person feel less hungry. This isn’t the case
in people with binge eating disorder; their elevated
leptin levels are actually associated with high levels of
endocannabinoids, which could help promote further
binge eating (Monteleone et al., 2005a). It’s not clear,
at this point, whether these alterations are a cause or a
result of regular binge eating.
When researchers compared leptin levels in women
with anorexia to women who had low weights for
other reasons, they found that leptin was significantly
higher in the women with anorexia. This blunted leptin
response could help explain why people with anorexia
are hyperactive and can continue starving themselves
for long periods of time. They are hungry, yes, but not
as hungry as they should be (Frederich et al., 2002).
In bulimia, leptin levels appeared somewhat lower than
expected, and lower leptin levels were associated with
more frequent binge eating (Jimerson et al., 2000). A
later study found that low leptin levels in women with
bulimia were also associated with more chronic, severe
illness (Monteleone et al., 2002).
Ghrelin is secreted by the stomach and acts opposite to
leptin. Whereas high levels of leptin help trigger satiety,
high levels of ghrelin help trigger hunger. Ghrelin levels
typically rise before a meal and decrease afterwards.
The hormone is thought to work in part by helping
to stimulate the brain’s reward system to encourage
eating. The links between ghrelin and eating disorders
aren’t quite as straightforward as those seen with
leptin. Scientists found that, in women with binge eating
disorder, ghrelin levels were lower than in women with
similar BMIs (Geliebter, Gluck, & Hashim, 2005). Other
researchers have found similar results (Monteleone
et al., 2005b), indicating that decisions about eating
aren’t dictated just by hunger and fullness, but by other
emotions as well.
When researchers measured ghrelin in women with
bulimia, they found that levels of this hormone didn’t
decrease as much as it did in control women. Since
women with bulimia don’t feel as full after a meal, they
may be more likely to binge or overeat (Monteleone
et al., 2003). In anorexia, ghrelin levels are elevated,
as expected with someone who is starving. During
the refeeding process, however, ghrelin levels drop
dramatically, which could help explain why many
people with anorexia struggle to put on weight: their
hunger signals aren’t working properly (Cano et al.,
2012). Page | 65