Title: ENDO: Tasting Food May Cause Elevated Brain Activity in the Obese
"ENDO: Tasting Food May Cause Elevated Brain Activity
in the Obese"
By Mike Fillon NEW ORLEANS, LA -- June 18, 2004 -- The
activity of some brain regions is especially high in
obese individuals compared to the nonobese, in
particular those regions involved in generating
emotions in response to and in recognition of the
taste of food. The new findings, reported here on June
16th at the 86th Annual Meeting of The Endocrine
Society, could help in the understanding of why some
people overeat, the researchers say. According to lead
author Angelo Del Parigi, MD, Clinical Diabetes and
Nutrition Section, Phoenix Epidemiology and Clinical
Research Branch, National Institutes of Health,
Phoenix, Arizona, it is believed that for some
individuals there is some irresistible force driving
them to eat more food than they need to, ultimately
increasing their risk of becoming obese. Dr. Del
Parigi says there are reasons to think that the
culprit may be emotions -- especially pleasure --
derived from the sensations of taste, smell and
texture, for example, generated by the passage of food
through the mouth. Dr. Del Parigi and colleges used
positron emission tomography imaging to measure
changes in regional cerebral blood, a marker of neural
activity, in 21 obese and 20 lean subjects before and
after they fasted for 36 hours then tasted a liquid
meal (Ensure Plus). The obese subjects were 10 males
and 21 females, and had a body mass index (BMI)
greater than 35 kg/m[2. Controls were 10 males and 10
females, and had a BMI below 25 kg/m2. Activity of
some brain regions, especially those involved in
generating emotions to and recognition of the taste of
food, was especially elevated in obese subjects.
"Abnormally high activity in the insular cortex region
of the brain, which responds to the sensory experience
of food, may put people at an increased risk for
obesity," Dr. Del Parigi explained.
Differences in changes to regional cerebral blood flow
(rCBF) were seen in several brain regions (middle
dorsal insula and cerebellum, precuneus, posterior
cingulate, and temporal and orbitofrontal cortices) in
obese as compared to lean subjects. The group
difference in the insula was observed in both men and
women separately. This activity is only partially
explained by the elevated glycaemia and high level of
disinhibition (i.e., the susceptibility of eating
behavior to emotional factors and sensory cues) that
characterise obese individuals, the researchers note.
Using multiple regression analysis, the researchers found
that
percentage of body fat (P =.04), glycaemia (P =.01), and
disinhibition (P
=.07) were associated with changes in rCBF measured in the
=insula (R2 =.45).
They do not know if this activity is caused by a
particular sensitivity to food stimuli in the
brains of obese individuals or if another aspect of
being obese changes the way the brain responds to
any stimulus.
The researchers believe that abnormal activity in the
insular cortex may represent a marker of increased
risk for obesity and, therefore, that continuing to
study the human brain and its response to food will
eventually answer why so many people eat more than
they should and are so susceptible to gaining weight.
[Presentation title: "Taste and Obesity: A Positron
Emission Tomography (PET) Study of the Brain Regions
Affected by Tasting a Liquid Meal after a Prolonged
Fast." Abstract #OR19-4]