If you ain't hungry, don't eat. That said, not everyone feels hunger in their stomach. Everyone has different hunger triggers, from becoming an utter grouch, to a headache, to grumbly stomach. If you're feeling/ noticing YOUR hunger symptom, eat. If food sounds like a good idea, and it's not boredom/ time of day related, eat. If food sounds like a good idea, but the thought of eating doesn't sound too appetizing, wait. You get the idea.