Higher levels of movement in the day (as well as less physical activity at night) were associated with more continuous and less disrupted sleep, which in turn predicted increased alertness from the participants in the morning.
Morning meals with more carbohydrates led to better alertness levels, while more protein had the opposite effect.
Lastly, a surge in blood sugar levels after breakfast – tested using a pure glucose liquid drink – was associated with reduced alertness.That said, in addition to reporting their daily behaviors, participants ate standardized meals and wore an accelerometer wristwatch (to measure sleep and activity) and a continuous glucose monitor (to measure blood sugar levels after meals), which is better than most studies that rely on questionnaires alone.