What are these calorie things?

Recently I read an interesting book by one of the nation’s leading nutritionists, Marion Nestle, called “Why Calories Count: From Science to Politics.”

Although “Why Calories Count” may sound like the title of the next new diet craze and a pitch to lose 20 pounds in a week by eating celery alone, it was actually an in depth look at the basic science behind calories and how they affect our weight.

Most people know the word ‘calorie,’ either having seen it prominently displayed on every piece of packaged food or used as a buzzword for different weight loss programs. But when asked to give a simple definition, we raise our hands and say “umm, something in food?”

So, what exactly are these calorie things we talk about?

The boring science-y definition of a calorie is, the amount of heat energy needed to raise the temperature of one gram of water by one degree centigrade, from 14.5 degrees to 15.5 degrees, at one unit of atmospheric pressure.

But that’s about as helpful as… well you know the rest.

An easier definition for us unscientific folks is

a calorie measures the potential energy in a food that can be used for work in the body, whether that work is chemical (on the cellular level) or physical (on the muscular level). These chemical reactions and muscular activities produce heat and that heat can be measured as calories.

As Nestle puts it “food provides energy that fuels the work that bodies do: breathe, circulate blood, keep warm, transmit nerve impulses, excrete waste, move.” And when we eat more calories than our bodies need in a given period of time, we store those excess calories as fat. This basic function has helped our species survive years of famine and food scarcity, but in our modern food abundant environment, this biological survival mechanism can cause more harm than good.