Increasing blood glucose level via breakfast meals is not connected with changes in delay discounting

Previous studies have revealed that increasing people's blood glucose level via drinking a soft drink containing sugar makes their financial decisions more future-oriented. This study extends these previous findings, testing whether the effect holds when blood glucose level is increased via intake of a normal meal (i.e., breakfast) rather than a sweet drink. Moreover, we test whether the size of the meal consumed (i.e., a normal vs. an oversized meal) can have a quantitatively different impact on levels of delay discounting. In two experiments using different time intervals between food consumption and discounting tasks (i.e., 60 min and 10 min), we successfully increased both blood glucose level and satiation level. Despite this, our results revealed that neither consumption of the meal itself nor the size of the meal influenced a preference for future rewards over present rewards. This suggests that satisfying hunger and increasing blood glucose level are not sufficient to make people more future-oriented.