Sniffing out obesity: Neurobiological mechanisms of odour-induced food cue reactivity

Imagine this situation: you walk past a bakery, and you sense the smell of freshly-baked bread. Mmm delicious, your mouth starts to water, and your stomach starts to growl.

Whether you would ignore these sensations and continue on your way, or enter the bakery to buy some croissants is determined by several factors, such as reward sensitivity and impulsivity. Increased reward sensitivity and lower impulse control appear to be critical features for overeating and hence obesity. This research proposal focusses on the underlying behavioural and neuronal mechanisms of these differences in food cue reactivity, in order to ultimately reduce those responses. As illustrated above, the olfactory sense plays a crucial role here.

In a randomized counterbalanced design, obese and lean subjects will participate in a series of experiments, in which I aim to identify the behavioural and neuronal (EEG and fMRI) responses to fat- and food odours, and subsequently try to infer causality between aberrant brain activation and eating behaviour using an interventional technique. I hypothesize that obese subjects will show no difference in their sensory response to food odours, but will have greater food intake and increased arousal of the autonomic nervous system after olfactory food cues and lower impulse control in a Go/No-Go task; they will show increased activity in brain networks involved in reward and palatability, especially towards fat odours, and will be less effective in recruiting brain regions involved in response inhibition. By means of transcranial magnetic stimulation of brain areas implicated in impulse control, I expect to be able to simulate heightened food cue reactivity in lean subjects.

This project is innovative in its approach to use olfactory stimuli to study heightened food cue reactivity in obesity, combine behavioural and neuroimaging methods, and the use of a cutting-edge intervention technique.

In addition, we are currently investigating patients who undergo gastric bypass surgery (RYGB). Their food preferences are thought to change to due surgery, from preferring high-fat, high-sweet foods to more healthy options afterwards. We are exploring whether these changes are due to a shift in the brain reward circuitry, comparing brain responses (fMRI BOLD) before and after surgery to palatable odors and pictures of foods differing in taste and energy content.

More research: Food-Gut-Brain interplay