calories explained

Most people in the Western world know or think they know what calories are. Yet it appears that few connect calories and energy. Witness to that the success of foods and drinks that promise to deliver energy without calories. Another common example of disconnect are the ubiquitous zero-calorie energy drinks. In case you wonder, the calorie is a unit of energy. There is no such thing as energy without calories and the expression makes about as much sense as saying length without meters (or feet) or weight without kilograms (or pounds).

The word calorie contains the root "calor" or heat and calories were originally defined as the energy required to heat a certain quantity of water (a gram) by a certain amount (a degree centigrade). The definition does not limit the calorie to heating however, and calories are a universal unit for energy. You can calculate the energy content of food, gasoline, natural gas, heating oil, and even nuclear materials, and express it in calories. Since the calorie is a rather small unit, it is not used all that often for gasoline or heating oil. Even the food calorie is in reality a kilo-calorie (or 1,000 calories).

Nutritionists will tell you that the average adult needs about 2,500,000 calories, or 2,500 "food calories" to stay healthy. Most of us consume quite a bit more and these excess calories are stored away as fat. Today, over half the population in the civilized world has excess calories stored away. The mantra in the West is how to loose weight, not how to stay properly fed.

The calorie is an older unit, and the official SI unit of energy is the joule. You may have noticed that some food packages express energy as both calories (Kcal to be exact) and KJ or kilo-joules. When you bought a portable heater or installed an air-conditioner, you may have noticed its rating in BTU or British thermal units. A BTU is approximately 252.5 calories. When you look at your gas bill, you may see yet another unit, called a Therm. A therm is 100,000 BTU or 25.25 million calories.

A kilogram of fat contains 9,000,000 calories or almost 36,000 BTU. A cubic foot of natural gas has approximately 1030 BTU or 260,000 calories. That is equivalent to 260 food calories, and you would need 10 cubic feet of gas per day to stay healthy (provided you could utilize the energy in natural gas).

Why go through this physics lesson?

The reason is to get a better understanding of how we stay alive. We stay alive because farmers produce excess calories that they do not need to feed their families. These excess calories can be traded (sold) to keep non-farmers alive. The non-farmers in turn mine and produce the other goodies we all use. That includes many items that farmers can use to make their yields go higher. And farm yields have increased significantly over the last 100 years. In the 1930's one farmer could sustain 10 people. These days, one farmer sustains 80 or more individuals. In a primitive economy, farmers could only produce enough food for 3-4 individuals. We have come a long way you might say. Yet there is no such thing as a free lunch.

One key reason why farmers have become so successful is because they put in a lot more energy to produce food. Whereas farmers were once limited to manual labor, supported by domesticated animals, today's farmers rely heavily on oil-powered machinery. They also depend on artificial irrigation systems, and heavy doses of fertilizers and pesticides. All in all, they are not just using more energy to produce food, they are using more energy per unit of food produced. What that means is that they are putting in more calories than they get out. And not just by a small margin. Estimates are that we consume 9-10 calories to produce one calorie worth of food. We are definitely entering a region of diminished returns.

All that excess food has had some serious consequences. Not only did we all get fatter, we also reproduced more. A lot more. The population boom of the last century was largely a result of the earlier "green revolution" in farming. Suddenly we could sustain a lot more people, and guess what, a lot more people quickly appeared. Now it seems, we are entering an era of more limited resources. Unfortunately, all those extra people are still with us. And they will be with us for a while to come. Not only that, but those people have already started reproducing too.

And therein lies our key problem.