So ... they tested whether the participants have more energy on sugar rush or hungry. And the ones having fuel had more mental endurance. Surprise. To actually

So ... they tested whether the participants have more energy on sugar rush or hungry. And the ones having fuel had more mental endurance. Surprise. To actually test the glucose hypothesis you have to compare fast with same calorie intake of sugar/starch/fat/protein/ and see the results. Currently it just means you make better decisions while not hungry.