How can you go from Starving, to stuffed without really eating?

Ok, so my kids claimed they were starving.

We had a large lunch at the mall (a treat)

They had munchies (i.e. samples) at Costco while shopping (again, a treat)

They had a real snack of (Costco-bought) granola bars.

When we arrived home. "MOMMMMMM, You didn't give us snack, we're starving!!!"

I gently reminded them, they had eaten, at which point they stopped complaining. But they said they wanted to eat dinner soon.

Dinner was cooked and served.

Yummy pizza (I was hungry - I hadn't had all their snacks, It tasted good). They barely touched their food.

When asked by their father "why aren't you eating"

"Dad, we're stuffed... we had too much to eat"

go figure.