Short CommunicationResponsivity to food stimuli in obese and lean binge eaters using functional MRI
Introduction
Functional brain imaging has been advancing rapidly from studies of sensation and cognition, to major psychiatric disorders, such as schizophrenia and depression, and more recently to eating disorders and obesity (Chowdhury & Lask, 2001). Using SPECT, Karhunen, Lappalainen, Vanninen, Kuikka, and Uusitupa, (1997) found increased activation in the right parietal and temporal lobe after visual food exposure in obese but not lean subjects. Wang et al. (2004) employing PET showed that food stimuli activated the orbitofrontal cortex (OFC) in lean individuals. In a recent fMRI study, healthy normal-weight women had activation of the medial and dorsolateral prefrontal cortex in response to high calorie food stimuli (Killgore, Young, Femia, Bogorodzki, Rogowska and Yurgelun-Todd, 2003). In the only imaging study in BED, Karhunen, Vanninen, Kuikka, Lappalainen, Tiihonen and Uusitupa (2000) using SPECT, observed greater left prefrontal and frontal activation following food exposure in BED than non-BED obese subjects. Hirsch, Moreno, and Kim (2001) developed an fMRI paradigm with multisensory stimuli to identify conjointly activated brain areas. We therefore employed fMRI, which has better spatial resolution than PET or SPECT, to examine conjoined brain activation to visual and auditory stimuli in obese and lean individuals, who were binge or non-binge eaters. We predicted that the obese binge eaters at the high end of both the weight and eating disorder spectrum would exhibit the most activation, especially in frontal and prefrontal cortical areas (involved in inhibition, decision making, ingestive behavior, and reward) in response to binge food stimuli.
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Subjects
Ten obese (BMI=29–41) and 10 lean (BMI 20–24) right-handed women participated. Exclusions included significant health problems, medications influencing body weight, smoking, alcohol >3 drinks/day or other substance dependence, suicidal ideation, psychotic disorder, claustrophobia, and presence of metallic implants, non-removable metallic dental retainers, or pacemakers. Subjects were weight stable for the past 3 months (±5%) and premenopausal, not pregnant or lactating, and not in treatment for
Results
The obese subjects had a higher body weight (P<0.0001), BMI (P<0.0002) and percentage body fat (P<0.001) than the lean subjects, without interactions by binge eating category (Table 1). There were no group differences in age or in depression and self-esteem. The binge eaters had higher scores on the BES (P<0.01), the total DEBQ (P<0.006) and all three subscales (P<0.02), without a weight-group interaction.
Conserved activation (strict) was seen only following binge food stimuli for the obese
Discussion
As predicted, brain activation areas were greatest for the obese binge eaters. Only they showed conserved activation (5/5) in response to binge food stimuli in the frontal precentral area, involved in planning of motor behavior (Chung, Han, & Kim, 2000), primarily in the ventral premotor cortex adjacent to the mouth region of the motor homunculus. This may reflect encoded or concurrent motor planning (Bischoff-Grethe, Goedert, Willingham, & Grafton, 2004) about eating such foods, including
Acknowledgements
Presented at the Society for the Study of Ingestive Behavior (SSIB) Satellite Symposium, Hueston Woods Resort, Ohio, July 18–20, 2004, chaired by Allan Geliebter and Harry R. Kissileff. The satellite was supported in part by the New York Obesity Research Center, SSIB, General Mills Foods, McNeil Nutritionals, Ortho-McNeil Pharmaceuticals, and Procter & Gamble. Some findings were also presented at NAASO, Nov 14–18, 2004, Las Vegas, Nevada. (Geliebter, Logan, Ladell, Feldman, Sharafi and Hirsh,
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