Body & HealthFact
Your stomach sends hunger on a timetable, not on demand.
Ghrelin is the hunger hormone. It is produced mainly in the stomach wall, rises before your usual mealtimes and falls again after eating. Its counterpart leptin comes from fat tissue and tells the brain over the long term how much energy is stored. Sleep loss shifts both: ghrelin goes up, leptin goes down, and appetite grows.
Useful: Hunger at your usual mealtime is often the hormone system's habit, not an empty tank.
Source: en.wikipedia.org