How many Calories in a cheeseburger?

Sometimes it seems like most of the people you meet are on a diet of some kind—either to lose weight, gain weight, or stay the same. In any case, it seems reasonable to assume that diets ultimately have to be about the amount of energy that you take in as food or drink, and the amount of energy that your body burns through exercise or just existing. Today we’ll talk about the units used to measure energy in food.
In the SI system, the unit of energy is the joule which is the amount of energy expended to exert a force of one newton through one meter of displacement. It can also be thought of as the amount of energy expended in one second by a one watt source, or the amount of heat generated when an electrical current of one ampere passes through a one ohm resistor for one second. Things start to get a little unstable when we want to think about the energy in food. Traditionally, food energy units are measured in Calories. In physics or chemistry another unit called the calorie (non-SI unit) of energy was equivalent to about 4.2 joules. However, it has been customary to measure food energy in units of 1000 calories, or kilocalories. Confusingly, the kilocalorie, in the context of food energy, is usually called the “Calorie”. It is common practice to distinguish between the two by capitalizing Calorie when referring to a kilocalorie, and leaving the original in lowercase: calorie. In any case, most of the food labeling that you see, when it treats energy, is referring to Calories, meaning kilocalories, or about 4.2 kilojoules.

So for this small cheeseburger from a popular fast food chain, whose identity has been tactfully removed, the advertised 300 Calories would contain about 1260 kilojoules of energy. Next time we’ll talk about conversion efficiency and energy consumption.