Why Frosted Pop-Tarts Have Fewer Calories Than Unfrosted Ones

Is it possible that adding frosting actually removes calories from food? No, it's not the latest internet diet fad: It's the perplexing conundrum of frosted versus unfrosted strawberry Pop-Tarts. As Quartz reports, on a fateful night in 2009, a Princeton student and his friends went on a snack run. They settled on the popular toaster pastry when they noticed something confusing about the nutrition labels. 

The student, Spencer Gaffney, made a blog post on University Press Club detailing his interesting observation. He and his friends wanted to see what the differences were between the frosted and unfrosted varieties of the treat, so they checked the nutrition facts on both. They quickly realized that the frosted version of strawberry-flavored Pop-Tarts had 10 calories less per serving than the unfrosted variety. They even compared the serving sizes to make sure the nutrition facts could be compared directly, but both referred to a single Pop-Tart.

But how could adding frosting and sprinkles decrease the calories on anything? The discrepancy seemed like an unsolvable mystery.

Unfrosted Pop-Tarts are thicker

But if Gaffney and his friends had taken a closer look at the label, they may have caught a critical clue. The key was in the weight of each food item. Six years after Gaffney's post, Quartz reached out to Kellogg's to get to the bottom of this mystery. A representative for the food manufacturing conglomerate put the debate to bed once and for all, saying, "Unfrosted Pop-Tarts have a slightly thicker crust to compensate for the lack of frosting, resulting in a few more calories per serving." 

This extra crust is shown on the food's packaging: The weight of the serving size. According to the nutritional label site Smart Label, an unfrosted strawberry Pop-Tart weighs 52g per pastry, while the label for a frosted strawberry Pop-Tart lists the serving weight as only 48g per pastry. That extra 4g of crust accounts for the additional 10 calories per pastry. No matter which variety you think is the best Pop-Tart flavor, it's clear that this case has been closed.