Calories: use them or wear them

Of all the bits of nutrition misinformation that annoy the heck out of me, perhaps the most annoying is the intentional misuse of the term “energy”—as in “high energy drink”, or “quick energy bar”. Energy actually refers to “Calorie”…would you knowingly buy a product that boasted it was high in Calories? I thought not. Discussion of Calories and energy makes me realize that many people don’t really understand just what a Calorie is and why an excess of them can make them fat. A Calorie is a unit of heat, after all, so why should eating heat contribute to weight?

A Calorie is a much broader (if you’ll pardon the expression) concept than just heat. A Calorie is an amount of any kind of energy. We could measure the energy of a speeding Ferrari if we wanted to. Energy is whatever makes things happen; call it “oomph” if you like. It comes in many forms: Physical motion (think Ferrari); chemical energy (think dynamite); nuclear energy (think reactor); electrical energy (think battery); gravitational energy (think waterfall); and yes, the most common form of all, heat.

It’s not heat that ends up on your hips, it’s stored energy—the amount of energy-for-living that your body gets by metabolizing food. And if metabolizing those French-fries produces more energy than you use up by getting off the couch, your body will store the excess as fat.

So then the next question is: how much energy is a Calorie and why do different foods “contain” (that is produce or yield) various numbers of Calories when metabolized? Well, since heat is the most common and familiar form of energy, the Calorie is defined in terms of heat—precisely how much heat it takes to raise the temperature of water. Specifically, the term is used by nutritionists and dietitians and is the amount of heat it takes to raise the temperature of a kilogram of water by 1 degree Celsius (actually a kilocalorie, also referred as a Calorie with a capital c). For Americans, who stay with the ancient and clumsy English system of measurement, a Calorie is the amount of heat it takes to raise the temperature of about 2 ½ cups of water by 1 degree Fahrenheit. For example, if you want to bring 2 ½ cups (20 oz) of water from 70 degrees up to the boiling point (212 degrees) you’d need to add 212 minus 70, or 142 calories of heat. I hope that’s clear!

Different foods, as everyone knows, provide us with different amounts of energy. The Calorie contents of various foods were originally found by actually burning them in an oxygen-filled container immersed in water and then measuring by how many degrees the water was heated (the apparatus is called a Calorimeter). You could do the same thing with a piece of apple pie to find out how much energy, or how many Calories, it releases. But is the amount of energy released when pie is burned in a laboratory the same as the amount of energy released when it is metabolized in the body? Remarkably, it is…even though metabolism releases its energy much more slowly, and thankfully without flames (heartburn doesn’t count).

The overall results are exactly the same: Food plus oxygen produces energy, and it’s a principle of chemistry that if the initial and final substances are the same, then the energy change is the same regardless of how the reaction took place. The only problem is that foods aren’t digested and oxidized completely in the body, so we actually get out of them somewhat less than their total energy content. On average, we wind up getting 9 calories per gram out of fat and 4 calories per gram each from both proteins and carbohydrates. So instead of running into the lab and setting fire to every food in sight, nutritionists just add up the number of grams of fat, protein and carbohydrate in a food and multiply by 9 or 4. You can do the same thing to check whether the calories listed on a food item are actually the same as that claimed by the manufacturer.

Your normal basal metabolic rate—the minimum amount of energy you use just to keep on ticking—that is by breathing, circulating your blood, digesting your food, repairing your tissues, keeping your body temperature normal and keeping your liver and kidneys and the like doing their jobs—is about 1 calorie per hour for every kilogram (2.2 pounds) that you weigh. That’s about 1,600 calories per day for a 150- pound male. But that can vary quite a bit depending on sex (women about 10 per cent less…wouldn’t you know), age, health, body size and shape, and so on.

Your bottom line (no pun intended) is how your intake of energy above and beyond your basal metabolic rate compares with your expenditure of energy by activity. For an average healthy adult man the usual recommendation is for an approximate daily intake of 2,700 calories and 2,000 for women—more for jocks and less for couch potatoes. As for the often-heard conundrum, “I eat a pound of fudge and I swear I gain four pounds”, the fact is that the most fat a person can gain by eating even a pound of 100 percent pure fat is only one pound. But I don’t recommend it.

Bearing in mind that 1gram of fat yields 9 Calories, then 454 grams (one pound) will yield 9x454 or 4,086 Calories. To allow for variations and for ease of calculations, nutritionists usually say that to burn a pound of fat one must consume 3500 Calories less than is expended. In other words, to lose a pound of fat in a week, you would need to deprive yourself of 3500 Calories over seven days, or 500 Calories per day. So, you can either increase your activity by 500 Calories or consume 500 Calories less than you need. If you need to gain weight (not the usual situation, but it does occur), then you must do the opposite.
In either case, be mindful of the fact that short of particular drugs (and caffeine is a drug), no food is going to give you energy that doesn’t involve Calories.