Lack of sleep

One of the reasons is that your brain depends on glucose, body has more endurance compared to the nervous system. Without enough rest, it will need more to stay active because you don't give it enough time to reset itself, called sleep. For example, I tend to stay up late because of work and that's the only time I start really craving for sugar, the idea of tuna doesn't sound appealing because the brain wants fast energy. That partly explains your ravenous hunger. Sleep is good.