Should You Trust the Calorie Counts on Your Food?

It’s complicated.

A food calorie is actually a kilocalorie, the unit of measurement that equals the amount of energy needed to heat one kilogram of water by one degree Celsius. But increasingly, nutrition scientists have argued that can mean different things for different people, depending how they prepare the food, their biology, and other factors.

The video above reaches back to the 19th-century birth of the calorie-counting process—and explains how it can lead us astray.