Background: In our increasingly obesogenic environment, the factors that enable some individuals to maintain control over their eating habits while others continue to develop obesity remain largely unknown. Behavioural attributes (traits) reflecting shared genetic and/or biological aetiologies likely interact with a person’s environment to drive overeating and, consequently, diet-induced obesity. Yet determining whether these behavioural attributes pre-date obesity or emerge as a consequence of extended high-fat/high-sugar food consumption in people with obesity is not a question easily answered in humans. This study utilized an established rat model of diet-induced obesity to determine, for the first time, specific neurobehavioral markers predictive of vulnerability to obesity.
Methods: Outbred Sprague Dawley rats (n = 35) were allowed free access to a high-fat/high-sugar diet (52% kcal fat) for 10-weeks then separated by weight gain into obesity-prone and obesity-resistant subgroups. Multidimensional behavioural profiling was performed prior to the diet period to examine predisposing risk traits (novelty seeking, anxiety-like behaviour, sign/goal tracking, attribution to incentive salience, cognitive inflexibility, impulsivity). Structural magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (FDG-PET) were conducted pre- and post- diet to examine structural and functional neuroimaging correlates of diet-induced obesity, and to determine the mechanistic trajectory towards the pathological state of obesity.
Results: The future tendency to develop diet-induced obesity was found to correlate with the reversal learning parameter α (p = 0.0409), which plays a central role in cognitive flexibility. MRI and PET scan analyses are still ongoing. It is hypothesised that, as brain plasticity mechanisms are tightly linked to learning, functional connectivity between the prefrontal cortex (PFC) and posterior dorsomedial striatum (pDMS) may be related to these findings.
Conclusion: Outcomes from this study can provide valuable insight into the neurobehavioral underpinnings of pathological overeating and diet-induced obesity, and allow early identification of at-risk individuals.