With pizza, here's my thought process. Firstly, overnight has no special significance for food. If you order a pizza at 9 PM and wake up at 7 AM, then that is r

With pizza, here's my thought process. Firstly, overnight has no special significance for food. If you order a pizza at 9 PM and wake up at 7 AM, then that is roughly the same as ordering pizza at 11 AM and eating it later at 9 PM. So just thinking in terms of hours, I think I've seen bad pizza (ie, pizza with visible mold growth) at 48 hours. I do not remember having any bad experiences with pizza that has been out for 12 hours or so. Usually my rule-of-thumb is around 12 hours, but if I'm desperate maybe 16 hours. If old pizza is just one of many food options, probably 8 hours. However, I think the author is being a bit silly with painting this as a matter of liar vs truth-teller. The truth is that without much more detail about the food and your environment, estimating time to spoilage is just an educated guess.