So, the University of Adelaide takes the crown for the most awesomely-named facility ever: the Nerve-Gut Research Laboratory. Rather than sit in said lab, admiring the well-chosen moniker, researchers have discovered that there's more to hunger than your stomach being empty or full — apparently, the time of day plays an important role too.
The study, published in the Journal of Neuroscience under the title "Circadian Variation in Gastric Vagal Afferent Mechanosensitivity", posits that the sensitivity of the nerves responsible for determining fullness are increased at night, while they're at their least sensitive during the day. As a result, we're inclined to consume more food while awake.
One caveat though — the university's release on the research states that their discoveries have been "made in laboratory studies, not in humans", with the paper's abstract referencing tests conducted on mice. That said, the authors are confident that humans have the "same variations in nerve responses".
It goes on to mention that their findings could help us to understand the health problems related to irregular eating and sleeping patterns, with shift workers cited as an example.