RYGB leads to changed responsivity of the frontoparietal control network that orchestrates top-down control to high-energy food compared to low-energy food and non-food cues, rather than in reward related brain regions, in a satiated state. Together with correlations with the shift in food preference from high- to low-energy foods this indicates a possible role in new food preference formation.

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Neural changes indicate improved response inhibition towards high-energy food cues, altered influence of metabolic control during response inhibition towards low-energy food cues and a more positive attitude to both high-energy and low-energy food after RYGB. Alterations in neural circuits involved in inhibitory control, satiety signalling and reward processing may contribute to effective weight-loss after RYGB.

Introduction: The endocannabinoid system (ECS) plays an important role in food reward. For example, in humans, liking of palatable foods is assumed to be modulated by endocannabinoid activity. Studies in rodents suggest that the ECS also plays a role in sweet taste intensity perception, but it is unknown to what extent this can be extrapolated to humans. Therefore, this study aimed at elucidating whether Δ9-tetrahydrocannabinol (THC) or cannabidiol (CBD) affects sweet taste intensity perception and liking in humans, potentially resulting in alterations in food preferences.Materials and Methods: In a randomized placebo-controlled, double-blind crossover study, 10 healthy males participated in three test sessions that were 2 weeks apart. During the test sessions, participants received THC-rich, CBD-rich, or placebo Cannabis by inhalation divided over two doses (4 + 1 mg THC; 25 + 10 mg CBD). Participants tasted seven chocolate milk-like drinks that differed in sugar concentration and they rated sweet taste intensity and liking of the drinks. They were then asked to rank the seven drinks according to how much they liked the drinks and were offered ad libitum access to their favorite drink. In addition, they completed a computerized food preference task and completed an appetite questionnaire at the start, midway, and end of the test sessions.Results: Inhalation of the Cannabis preparations did not affect sweet taste intensity perception and liking, ranking order, or ad libitum consumption of the favorite drink. In addition, food preferences were not influenced by the interventions. Reported fullness was lower, whereas desire to eat was higher throughout the THC compared to the CBD condition.Conclusions: These results suggest that administration of Cannabis preparations at the low doses tested does not affect sweet taste intensity perception and liking, nor does it influence food preferences in humans.

11 modulation on sweet taste intensity perception and liking, and food preferences are investigated in this thesis. Neurophysiological perspective: brain imaging Neurophysiological responses can also provide more insight into underlying mechanisms of food reward and therefore brain imaging studies have been performed. Often used paradigms are food versus non-food viewing paradigms (see e.g. Killgore et al., 2003; LaBar et al., 2001), which are suggested to signal food anticipation (McCrickerd and Forde, 2016). In general, these studies find increased activation in reward-related brain areas, including the orbitofrontal cortex, striatum and insula, for viewing of foods over non-foods. In addition, looking at pictures of high-energy foods elicits more activation than looking at pictures of low-energy foods (van der Laan et al., 2011). Other studies used odours to signal food anticipation. In these studies, an olfactometer was used to deliver specific odours for short periods of time, that is, seconds. Similar to looking at pictures, smelling food odours elicits more reward-related activation than smelling non-food odours