Mapping the 'Sweet Brain' in Healthy Participants
Condition: Obesity; Sweeteners
Study type: Interventional

Summary: 
      The human brain has a central role in regulating appetite and food intake. It integrates many
      metabolic, hedonic and trait-related signals that affect eating behaviour and determine when
      and how much we eat. The effects of non-nutritive sweeteners (NNS) that provide sweet taste
      with no calories on appetite, food intake thus weight status remain a subject of debate. In
      this study, the investigators aim to investigate whole brain response to the ingestion of
      beverages sweetened with caloric sugars (glucose, maltodextrin) or NNS (stevia) as well as
      neural substrates of attentional bias to food (pre-and post consumption) in healthy lean
      participants.
    

Detailed description: 
      Non-nutritive sweeteners (NNS) are zero or no calorie alternatives to caloric sugars and
      their role in appetite and weight status remains inconclusive. NNS similarly as caloric
      sweeteners activate the oral sweetness receptors and conscious perception of sweetness.
      However caloric sugars and NNS differ in their metabolic fate after ingestion, so that
      caloric sugars lead to raised blood glucose, insulin and satiety inducing gut-peptide levels
      after meals, but NNS do not influence postprandial metabolism. A recently proposed model
      suggests that metabolic signals may have indirect effects on food reward processing via
      alterations in higher cognitive function such as attention (Higgs et al. 2017), the role of
      sweetness in this model is yet to be examined.

      In the proposed study stevia-sweetened beverage will be used as the NNS, glucose-sweetened
      beverage as the caloric sweetener, water as a non-sweet non-caloric control and maltodextrin
      as a non-sweet caloric control. The study has two aims: first to investigate whole brain
      responses following the oral consumption of caloric sugars versus NNS using and physiological
      MRI, and second to examine the neural correlates of the attentional bias to food cues
      following the consumption of caloric sugars- vs. NNS-sweetened beverages using task-based
      functional Magnetic Resonance Imaging (fMRI).

      In this study participants will be asked to come to the imaging facility on four separate
      occasions, corresponding to the four study beverages, glucose, stevia, maltodextrin and
      water. Before coming to an imaging session participants should consume a breakfast of their
      preference at home (which will be repeated before each session) and then fast for 3-4 hours.
      Upon arrival subjects will fill in their mood ratings, and the breakfast composition
      questionnaire and will be ready to start. Firstly, neural responses will be measured (before
      consumption of the study beverages) while subjects perform a food visual dot probe task (VPT)
      previously validated to show differences in attentional bias to food between fasted and fed
      states (Stamataki et al. 2019). Secondly, a physiological MRI measurement will be performed
      (Little et al. 2013) which will last 40 minutes. Third, subjects will perform again the VPT
      (after the consumption of the study beverage) whilst an fMRI measurement will be performed.
    

Intervention name(s): Stevia; Glucose; Maltodextrin; Water
Intervention type(s): Dietary Supplement; Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): Participants will be administered one of the study beverages at each one of the 4 imaging sessions.; Participants will be administered one of the study beverages at each one of the 4 imaging sessions.; Participants will be administered one of the study beverages at each one of the 4 imaging sessions.; Participants will be administered one of the study beverages at each one of the 4 imaging sessions.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Counter-balanced, double-blind, crossover, within-subject design.
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Basic Science