People hold diverse beliefs about obesity causes which can be biological, behavioural, psychological and environmental. In a society with increasing levels of information about obesity causes and healthy dietary behaviour, it is important to understand how that information influences eating behaviour. This study aimed to investigate whether inaccurate thinking about causes of obesity is linked to eating behaviour and actual weight. In a cross-sectional study, 176 participants performed causal reasoning tasks with obesity-related and general content and completed several validated questionnaire measures in order to examine relationships between causal conditional reasoning and factors including weight, personality, and behaviour. Preliminary findings show a significant difference between reasoning in the general and obese tasks, with more accurate responses evident in obese reasoning paradigms. Restrained eating negatively correlated with obese but not general reasoning, and this significant effect increased for participants with a BMI >25. When comparing current dieters and non-dieters there were significant differences including dieters exhibiting significantly poorer obesity reasoning, but not general reasoning, than non-dieters regardless of BMI. This indicates that the act of dieting reduced individuals’ ability to make accurate obesity related causal judgments. To conclude, accuracy in causal reasoning judgements appears to differ depending on context. Moreover, eating behaviour influences accuracy with both restrained eating behaviour and dieting negatively affecting accuracy of obese, but not general, reasoning. The findings indicate that logic does play a part in obesity with an interaction between reasoning and behaviour which warrants further investigation.