Effect of satiation on brain activity in obese and lean women

Objective: To investigate the response of the brains of women to the ingest ion of a meal. Research Methods and Procedures: We used measures of regional cerebral bloo d flow (rCBF), a marker of neuronal activity, by positron emission tomograp hy to describe the functional anatomy of satiation, i.e., the response to a liquid meal in the context of extreme hunger (36-hour fast) in 10 lean (BM I less than or equal to 25 kg/m(2); 32 +/- 10 years old, 61 +/- 7 kg; mean +/- SD) and 12 obese (BMI greater than or equal to 35 kg/m(2); 30 +/- 7 yea rs old, 110 +/- 14 kg) women. Results: In lean and obese women, satiation produced significant increases in rCBF in the vicinity of the prefrontal cortex (p < 0.005). Satiation als o produced significant decreases in rCBF in several regions including the t halamus, insular cortex, parahippocampal gyrus, temporal cortex, and cerebe llum (in lean and obese women), and hypothalamus, cingulate, nucleus accumb ens, and amygdala (in obese women only; all p < 0.005). Compared with lean women, obese women had significantly greater increases in rCBF in the ventr al prefrontal cortex and had significantly greater decreases in the paralim bic areas and in areas of the frontal and temporal cortex. Discussion: This study indicates that satiation elicits differential brain responses in obese and lean women. It also lends additional support to the hypothesis that the paralimbic areas participate in a central orexigenic ne twork modulated by the prefrontal cortex through feedback loops.