Differences in brain responses between lean and obese women to a sweetened drink

Abstract

Background: Ingestion of sweet food is driven by central reward circuits and restrained by endocrine and neurocrine satiety signals. The specific influence of sucrose intake on central affective and reward circuitry and alterations of these mechanisms in the obese are incompletely understood. For this, we hypothesized that (i) similar brain regions are engaged by the stimulation of sweet taste receptors by sucrose and by non-nutrient sweeteners and (ii) during visual food-related cues, obese subjects show greater brain responses to sucrose compared with lean controls.

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

Key results: Viewing food images after ingestion of either drink was associated with engagement of similar brain regions (amygdala, hippocampus, thalamus, anterior insula). Obese differed from lean subjects in behavioral and brain responses rating both beverages as less tasteful and satisfying, yet demonstrating greater brain responses. Obese subjects also showed engagement of an additional brain network (including anterior insula, anterior cingulate, hippocampus, and amygdala) only after sucrose ingestion.

Conclusions & inferences: Obese subjects had a reduced behavioral hedonic response, yet a greater engagement of affective brain networks, particularly after sucrose ingestion, suggesting that in obese subjects, lingual and gut-derived signaling generate less central hedonic effects than food-related memories in response to visual cues, analogous to response patterns implicated in food addiction.

Figure 1

Study protocol. On the scanning day, subjects underwent three types of scans: a brief structural scan, a resting state scan, and a food images scan. Ten minutes before both the resting state and food images scans, subjects received a fullness questionnaire (FQ) and either a non-nutrient sweetened drink or a sucrose beverage. Immediately prior to scanning, subjects were given another FQ as well as a palatability questionnaire (PQ). This scanning day was repeated with the order of the drinks counterbalanced. The resting state scan along with the drink and questionnaires given prior to the scan were analyzed together as study 1 (results presented in a different paper). The food images scan and accompanying drink and questionnaires (study 2) are analyzed in this article.

Figure 2

Obese subjects show greater engagement of brain network including posterior INS (left panel) and bilateral amygdala (right panel) to viewing food images, using a multivariate functional magnetic resonance imaging analysis approach, as described in the Methods section. A blue circle marks respective brain regions.

Figure 3

Obese subjects had greater engagement of a network including the anterior INS (blue circle) following the high-calorie sucrose beverage, using multivariate functional magnetic resonance imaging analysis approach, as described in the Methods section (P < .001).