, founder of Healthengine.us and senior product manager at Amazon AI, Mondays are a notoriously bad day to stop at a fast food chain for several reasons. The first is due to staffing gaps. "Weekends attract this chain's top performers, so Mondays tend to be manned by novice staff who do not prepare food the same way every time, so there are many order mistakes," Singh said. 

There's also the question of ingredient freshness, as Anthony Bourdain made famous with his rule about skipping the Monday fish special (though he later repented, to an extent). "[Many perishable foods] also have a delivery schedule on Tuesday, which means that items like buns and fries that are kept under heat lamps used during Monday service are out of date and stored for over a week," Singh warned. You also want to avoid eating anything that could have potentially come into contact with stagnant cooking oil that has been sitting around all weekend long. The expert elaborated, "This creates off-flavors and poses a risk to food safety due to FIFO (first-in, first-out) protocols failing to be performed."