The Biggest Rumor About Fast Food Spoiling, Debunked

At the end of the perhaps less-than-accurate documentary "Super Size Me," filmmaker Morgan Spurlock demonstrates what allegedly happens when fast food is left out for weeks on end — nothing. It's easy to find other experiments online that replicate these results and prop up a persistent urban legend: that fast food does not spoil and does not decompose like so-called "real food."

However, the rumor that fast food never goes bad is just a myth. The truth behind why certain fast food items never seem to rot is simple. Most fast foods are high in salt and low in moisture. They dry out before they can grow mold. It's the same reason why foods like beef jerky and beans last so long in cool, dry conditions.

In moist environments, fast food burgers, fries, and tacos — just like any food — will indeed go bad. Despite explanations that attempt to debunk this, there are many reasons people continue to believe the rumor that because fast food menu items can be pretty unhealthy, they must be unnaturally indestructible.

Why do rumors that fast food never goes bad persist?

Under the right conditions, any food will spoil, even if some of the signs are harder to spot than others. Fast food is no different. Even so, one of the most persistent (and debunkable) rumors about drive-through burgers and fries is that they're virtually indestructible and will last forever.

It seems every few months, another example of this alleged phenomenon goes viral. A 2020 TikTok video shows a 24-year-old McDonald's burger that looks almost fresh, and a hostel in a small town in Iceland still has the country's last-ever Big Mac (sold in 2009) on display. Another TikTok shows well-preserved fast food pizzas, and there is a chiropractic office in Michigan that reports a Taco Bell meal didn't mold or smell after two years.

What makes this legend so attractive? A major reason is that fast food does indeed contain plenty of surprising ingredients, including potentially harmful items or toxic preservatives, and the sight of a mummified burger makes for a super-shareable visual association. But even if the narrative that fast food never rots is an impactful reminder that going through the drive-through every day may not be the most nutritious option, it's important to remember that this rumor is not exactly true.