Bloody buffet food

Why is it that even though I eat a filling lunch, if there is leftover buffet food in the office, I have to eat it?

I managed to resist the scones that were there earlier, but this food has been looking at me funny all afternoon and - just as I'm about to leave - I just ate a sandwich and a handful of crisps.

Defeated by a crinkly-cornered sandwich from a leftover buffet lunch. Tragic really.