Human Food addiction?
Marcia Levin Pelchat, Ph.D.
Monell Chemical Senses Center
Outline
Most discussions of food addiction focus on
parallels between drug craving and food
craving mechanisms:
Behavioral
Neurochemical
Neuroanatomical
Hippocampus Insula caudate
A dependent person has to meet at
least 3 of the following criteria:
Taken in larger amounts or over a
longer period than intended.
Persistent desire or unsuccessful
attempts to cut down or control
use.
Large amounts of time spent
seeking the substance, using it, or
recovering from its effects.
Tolerance
Withdrawal – almost always
includes craving.
Important social, occupational, or
recreational activities given up or
reduced because of substance use.
Continued use despite knowledge
of harmful consequences.
Bulimia?
Obesity?
DSM-IV TR, American Psychiatric Association Dietary restraint?
Craving is an intense
desire to eat a particular food
or to engage in a particular
activity.
Craving - Nutritional
Impact
Cravings predict high BMI
(Wurtman, 1988; Schlundt et al., 1993; Delahanty, Meigs, Hayden, Williamson,
& Nathan, 2002).
Snacking/compliance with
dietary restrictions (Sitton, 1991; Basdevant,
Craplet, & Guy-Grand, 1993; Schlundt et al., 1993; Fedoroff, Polivy, & Herman,
1997).
Binge eating/bulimia Drewnowski, 1991;
Gendall & Joyce, 2001; Waters, Hill & Waller, 2001; Hetherington &
Macdiarmid, 1993
Liking, wanting, craving , and
reward -defined
Liking – pleasantness or hedonic response or
evaluative response to a stimulus.
Wanting – desire
Craving – very strong, desire.
Reward enhances desire and pleasure
Pleasure may be rewarding, but other reinforcers
may be rewarding without conscious pleasure e.g.,
repletion.
Specificity
These concepts have specific
objects of reference
Unlike hunger
Craving: sensory template
Olds & Milner (1954)
Rats press to receive electrical
brain stimulation.
Will maintain rates as high as
7000 presses per hour
Choose self-stimulation in
preference to food and sex
“pleasure, or reward circuit”
Medial forebrain bundle
Neurotransmitter =
Mesolimbic dopamine
Pleasure vs. desire
Reports of patients implanted
with self-stimulation electrodes:
•Sensation not pleasant!!!
•Yet, compelled to continue
pressing the for stimulation (Heath, 1963).
Drug addicts crave, but do
not enjoy drug, (Robinson & Berridge, 1993).
Happens with food as well 2 deep stimulation electrodes
(Pelchat & Schaeffer, 2000).
Neurotransmitters have similar
effects on desire for foods and
drugs:
Reward Circuit
•Dopamine
•Endogenous opiates
Striatal dopamine released
by feeding and by cocaine
Dopamine release
induced by feeding in
dorsal putamen and
caudate. Coronal section
from raclopride binding
study (Small et al., 2003).
Change in binding
correlated with rated
meal pleasantness but
not hunger/satiety.
From Small et al., 2003
•Drug abuse associated
with decrease in sensitivity
of the dopamine-reward
system
•Same seen in obese
individuals
Decreased raclopride binding means fewer D2 receptors
No difference in global glucose metabolism
Inverse relationship between D2 receptors and BMI
Direction of causality????
Wang, Volkow, et al., 2001
Opiates?
BUT Dopamine depletion or
blockade doesn’t diminish
pleasurable responses to
palatable foods in animals or
humans (Berridge & Robinson,
1998).
Endogenous opiates: Lead to
higher levels of striatal
dopamine - rewarding properties
of alcoholic beverages and of
sweet (or palatable) foods
Through other pathways,
play a role in pleasure.
Neurochemistry of pleasure
Naltrexone reduces
short term food
intake
May be limited to
palatable foods
Does lead to reduced
pleasantness ratings
(Yeomans & Gray, 2002)
Doesn’t appear to affect
hunger
Doesn’t lead to weight
loss (Mitchell et al., 1987)
Nutritional deprivation is not necessary
Pelchat & Schaeffer, 2000
Method – fMRI study
• 2 groups – monotonous diet (MD) for 1
1/2 days or unrestricted diet with
sampling of monotonous diet (ND).
• Bold fMRI, 4T(tesla) scan
High field gives better signal-to-noise
ratio & visualizes capillaries which gives
better resolution.
• Imagine two liked foods or imagine
monotonous diet in block design.
• Why use imagination rather than
video?
Pelchat, Johnson, Chan, Valdez & Ragland, 2004
Behavioral results
All participants in the MD group
experienced cravings when
imagining the liked foods.
No one experienced cravings
when imagining the monotonous
diet.
We were very successful at
turning craving on and off in 30
sec bins.
Pelchat et al., 2004
Craving or liking- specific activation?
Liked - Monotonous
MD group ND group
No above threshold activation
fusiform gyrus (-36, -38, -12; Z=4.5);
parahippocampal gyrus (-20, -30, -12; Z=4.0);
amygdala (28, -6, -12; Z=3.6); caudate nucleus (-4,
6, 16; Z=3.5; 0, 6, -4; Z=3.2); putamen (24, 10, 0;
Z=3.0); cingulate gyrus (8, -42, 16; Z=3.6); and
middle frontal gyrus (-16, 2, 44; Z=4.1).
Brain activation associated
with food craving
Hippocampus Insula Caudate
Pelchat et al., 2004
Results and Conclusions - fMRI
Food craving accompanied by
activation of structures involved in
memory, emotion, decision making,
and habit learning.
All of these structures have been
reported to be activated in drug-
craving studies.
Importance of memory and habit in
food craving.
Conditioning
• Conditioning effects used to explain
compulsion to use drugs long after
withdrawal (e.g. O’Brien et al., 1998).
• Nutritional deprivation not
necessary to produce food cravings
(Pelchat & Schaeffer, 2000).
• Sight, smell or imagery may trigger
food craving (Federoff et al., 1997; Tuomisto et al.,
1999).
Externality scale (van Strien et al., 1986)
Externality hypothesis (e.g. Schacter, 1971).
Craving may be an acquired
response based on repeatedly eating
the craved food when hungry (Gibson &
Desmond, 1999; Pelchat & Schaeffer, 2000).
Current emphasis
How are cravings learned?
Can we produce cravings for a
neutral or disliked food?
Healthy foods?
fMRI tool
Conclusions
Many parallels between feeding behavior and
drug addiction.
Neuropharmacology
Neuroanatomy
Behavior/learning
Many studies of obesity focus on mechanisms of
hunger.
Treatments for drug abuse focus on craving,
impulsivity, learning.
Diet failure – always due to hunger?
Should we outlaw tasty food?
Many don’t become addicted to food.
Like alcohol – lessons from prohibition.
Predisposition interacts with experience to
produce eating-related problems. E.g.
Hoebel/Corwin intermittent access.
Use lessons from drug addiction to treat
obesity.