Several theories suggest that goal conflict leads to loss of control, but few studies have tested this proposal objectively. A transdiagnostic approach to CBT based on Perceptual Control Theory proposes that conflict between superordinate goals is at the heart of loss of control, and in turn, psychological distress. This study used the example of goal conflict around eating in a non-clinical sample as proof-of-concept to test whether it predicted loss of control. We examined whether the conflict regarding reasons to eat tasty food (e.g. ‘Eating tasty food helps me feel better’) versus reasons not to eat tasty food (e.g. ‘I want to lose weight’) correlated with weight fluctuations over 6 weeks in 33 students. At baseline, higher levels of goal conflict were associated with greater state and trait food cravings, and more problems with control over eating. As predicted, people with higher levels of goal conflict showed greater weight fluctuation. The effect diminished when controlling for trait food craving, and exercise fluctuation remained an independent predictor. We discuss the implications for future research on goal conflict, and for interventions that raise awareness of goal conflict to improve wellbeing via the enhancement of self-control.