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Differeneces in Brain Responses Between Lean and Obese Women to a Sweetened Drink


Background: Ingestion of sweet food is driven by central reward circuits and restrained by interoceptive satiety signals. Obesity is in part related to an upregulation of these reward mechanisms in association with a downregulation of vagally mediated satiety mechanisms. The specific influence of sucrose intake on central affective and reward circuitry, and differences in these influences in the obese population is incompletely understood.

Hypotheses: 1) Similar brain regions are engaged by the stimulation of sweet taste receptors by sucrose and by non-nutrient sweeteners. 2) During visual food related cues, obese subjects show greater brain responses specifically to sucrose compared to lean controls.

Methods: In a two-day, double blind, crossover design, 10 obese and 10 lean healthy females received either a sucrose or a non-nutrient sweetened beverage prior to viewing agreeable food or neutral images. BOLD signal was measured using a 1.5Tesla MRI scanner.

Results: Viewing food images after ingestion of either the sucrose or the non-nutrient drink was associated with engagement of similar brain regions, including the amygdala, hippocampus, thalamus and dorsolateral prefrontal cortex, Obese differed from lean subjects in both behavioral and brain responses: While obese subjects rated both beverages as less tasteful and satisfying, they showed greater brain responses. Obese subjects also showed engagement of an additional brain network (including anterior insular and anterior cingulate cortices, hippocampus, amygdala), and this was only seen after sucrose ingestion.

Conclusion: Obese subjects had a reduced behavioral hedonic response yet a greater engagement of affective brain networks in response to food images, particularly after sucrose ingestion. These findings suggests that in obese subjects lingual and gut derived signaling generate less central hedonic effects than recalling memories of food experiences in response to visual cues, analogous to response patterns implicated in food addiction.

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