"We're sorry to report that sometimes, impulse gets the best of deliverers, and they violate their sacred duty by taking some of the food!" US Foods said in a statement.
When asked if they minded if their driver snagged a few fries, the average customer response was an 8.4 out of 10 — 1 represented "no big deal" and 10 signified "absolutely unacceptable."
To remedy the problem, 85% of customers recommended adding tamper-evident labels or packaging, which commonly comes in the form of a sticker seal.
Some delivery services already have strategies in place.
Postmates told NPR that food tampering cases account for less than 0.06% of the reports it receives. The delivery service, however, still requires "each person who completes a delivery using Postmates to expressly agree that all food and goods delivered will arrive in a tamper free form and in compliance with all applicable food health and safety laws."
In an online chat, a Grubhub representative said if a customer suspects that some of the food is missing, the company will potentially open an investigation and make a refund.
UberEats and DoorDash haven't responded to NPR's request for comment.
In its delivery guidelines, UberEats said it will deactivate any account with fraudulent activity or misuse, including "claiming to complete a delivery without ever picking up the delivery item; and picking up a delivery item but not delivering it in full."
Doordash directs its drivers to not open food containers or tamper with the order in any way. If a customer suspects food tampering, the company states it will deactivate the driver's account.
Overall, restaurant food delivery services are a growing business, transforming the way people receive their meals.
In 2018, UBS found that on average, food delivery platforms were in the top 40 most-downloaded apps in major markets.
"We think it's possible that by 2030 most meals currently cooked at home will instead be ordered online and delivered from restaurants or central kitchens," according to UBS.
Copyright 2019 NPR. To see more, visit NPR.org.