Grab to eat! Eating motivation dynamics measured by effort exertion depend on hunger state

A crucial challenge in investigating motivated human eating behaviour is to go beyond subjective measures, by developing reliable methods capable of objectively quantifying the dynamic aspects of appetitive motivation. We developed and tested a novel effort-based task (Grab-to-Eat Task (GET)), utilising handgrip force as a motivational measure, to capture eating motivation dynamics throughout consumption. Sixty normal-weight young adults were allocated to one of two hunger state conditions (hungry or satiated) and performed a continuous reinforcement-based task, during which sips of chocolate milk were self-administered with a handgrip force transducer. Motivation was covertly assessed by the magnitude of effort exertion towards each sip. Cumulatively, hungry subjects exerted more effort and consequently consumed more chocolate milk than satiated ones. Effort exertion declined throughout consumption in both groups, with the rate of decline being two-fold greater in hungry subjects. Furthermore, effort exerted in the initial stages of consumption predicted subsequent intake. Present results fit in the theoretical framework of reward-related motivation and suggest that the developed paradigm is sensitive to eating motivation dynamics throughout consumption and to differences in eating motivation related to hunger state. Further validation, ideally involving functional neuroimaging, would be imperative. In the future, this paradigm could be used to investigate eating motivation dynamics in various populations, conditions and food products.