Unhealthy food bias in food addiction: behavioral evidence from a probabilistic image choice task

Food addiction (FA) shares behavioral and neurobiological similarities with substance use disorders, but objective behavioral measures of FA are lacking. We aimed to adapt the Probabilistic Image Choice (PIC) task to assess behavioral bias toward unhealthy food, and to determine its association with FA and obesity. Cross-sectional study with a 1-year follow-up in a subset of participants. Online study with participants from the UK and Ireland. 415 adults (50% women) recruited via the Prolific platform, with 72 completing a follow-up assessment after 12 months. Participants completed the Yale Food Addiction Scale (YFAS 2.0), reported height and weight for BMI calculation, and performed the adapted PIC task featuring four image categories: neutral, pleasant, healthy food, and unhealthy food. Primary outcome measures included unhealthy food bias (difference between unhealthy and healthy food image selections) and its relationship with food addiction and obesity status. Individuals with severe FA or obesity showed greater selection of unhealthy food images compared to those without food addiction or obesity. Gender analyses revealed that unhealthy food bias was larger in women than in men with food addiction. Test-retest analysis showed high stability of the unhealthy food bias over a one-year period. The FA PIC task provides an operant behavioral measure of unhealthy food bias that is associated with food addiction, particularly in women. The stability of this bias over time suggests it may represent a trait-like characteristic with potential diagnostic and prognostic value for FA and related disorders. People often struggle to regulate their eating behaviors, especially when it comes to foods high in sugar, fat, and salt. According to some researchers, this difficulty might be related to a behavioral process similar to substance use disorders. To test this idea, we used a computer task where people choose which pictures they want to see from different categories: everyday objects, pleasant scenes, healthy foods like fruits and vegetables, or unhealthy foods like pizza and cookies. We found that people showing signs of food addiction consistently chose to look more at pictures of unhealthy foods compared to healthy foods. This pattern was especially strong in women. When we tested some people again a year later, their choices remained remarkably similar, suggesting this preference is stable over time rather than just a temporary state. Importantly, not everyone who is obese shows this pattern, and not everyone with food addiction signs is obese, showing these are related but different processes. This behavioral task might help doctors and researchers better understand the behavioral and neurobiological mechanisms underlying food addiction. This understanding may eventually lead to more personalized approaches to supporting people struggling to control their eating behavior.