I heard a sleep doctor give a lecture awhile ago who repeated the advice of eating a hearty breakfast, primarily as a way to encourage good sleep. She said that our bodies interpret food within 30 mins of waking up as a signal that food is abundant, which lowers our general stress levels and makes it easier to sleep.

Skipping breakfast, on the other hand, signals food scarcity or higher predator threat, increases stress hormones, and encourages lighter sleep so you can be woken more easily.

No idea how true it actually is, but it seems to make sense from an evolutionary standpoint.