Attitude Media Health Essay

What is a calorie, and what does it have to do with Bill Cosby?

We’re told that we should watch our calories to maintain proper weight, and many people do so, but without having any idea as to what a calorie really is. Never have so many cared so much about something they understood so little.

Up until the late 1700s it was thought that there were really only 4 irreducible elements that formed everything – earth, water, air, and fire. Then scientists started to figure out that each of these was, in fact, the combination of other elements. A small group of scientists, or natural philosophers as they were sometimes called, principally curious laymen with little formal training in England and France, exchanged information and results on their various studies. In 1789 the great French scientist Antoine Lavoisier published a whole new system of naming chemicals, including the term “caloric”, which meant heat as a substance. Now we know that heat is not a substance, but a byproduct of the consumption of energy.

Early in the history of the word, it was even part of a scurrilous attack: When the great Victorian scientists Humphry Davy and Thomas Beddoes were accused of being “newfangled Doctors pimping for Caloric” it was because their experiments with nitrous oxide were alleged (falsely) to be Bill Cosby type attempts to drug women and take sexual advantage while they were under the effects of what we now know as “laughing gas”.

Why were Davys and Beddoes connected with “caloric” when nitrous oxide had nothing to do with the study of heat or calories? Probably because Davy’s earliest published work in 1799 (“An Essay on Heat, Light, and the Combinations of Light) was a refutation of Lavoisier’s caloric, arguing, among other points, that heat is motion but light is matter.

So, back in the day, calories were connected, in sometimes bizarre ways, with laughing gas, alleged attacks on women, motion and heat. But all you care about is why they make you fat. Despite some wrong turns that are part of the normal scientific process, the early association of heat with calories was correct.

You might reasonably wonder what heat has to do with making you fat. When you eat a piece of cheesecake or an ice cream cone, or drink a Coke, you don’t associate that action with “heat”. Calories as reported on your favorite food are actually a heat measurement, but it’s not obvious what heat has to do with the energy in food. The answer lay in physics. The total energy in any system, in this case an item of food, equals the sum of the work and heat. We cannot measure the ‘work’ in a quantitative way, because work is very dependent on the vehicle in which the work is being done. A gallon of gasoline will drive a small car a lot further than a big truck, and 1000 calories will power a small girl a lot longer than an NFL lineman. But heat can be measured objectively, independent of the mechanism that burns it. So if we place the work at zero and measure all of the heat in our sample, we can determine the amount of energy the sample contains; heat is a proxy for energy.

The Calorimeter is a tool that is used to do just that. The sample is burned in an insulated container and the change in water temperature is measured. The amount of energy in the sample can then be calculated, and when reported on food labels, is called a Calorie. Food manufacturers no longer actually test food for heat output; calories are calculated based on the components of food. This is what the Scientific American website has to say about measuring calories:

“The Nutrition Labeling and Education Act of 1990 (NLEA) currently dictates what information is presented on food labels. The NLEA requires that the Calorie level placed on a packaged food be calculated from food components. According to the National Data Lab (NDL), most of the calorie values in the USDA and industry food tables are based on an indirect calorie estimation made using the so-called Atwater system. In this system, calories are not determined directly by burning the foods. Instead, the total caloric value is calculated by adding up the calories provided by the energy-containing nutrients: protein, carbohydrate, fat and alcohol.”

At the start of this essay, we mentioned that early scientists believed that all the matter in the universe was formed by some combination of earth, water, fire, and air. Now scientists believe that everything you eat or drink can be measured in terms of the effect on your weight by only 4 factors: protein, carbohydrate, fat and alcohol. Are they right, or is that analysis as primitive as earth, water, air, and fire? We'll explore that question in our next essay on calories. Stay tuned.