Wow, How many Calories is in that?

Every food has an available amount of energy. How exactly can you figure out an idea of what that number is?

Primer on Nutrients

A nutrient is a chemical substance used by the body for energy. Different foods have different amounts of energy.

There are six major classes of nutrients the body uses for growth, maintenance and repair:

  1. Water
  2. Minerals
  3. Carbohydrates
  4. Fats
  5. Proteins
  6. Vitamins

These nutrients can be classified by the amount the body needs of them, large and small or, macro and micro. Whether they are organic (have carbon) or inorganic (do not).

When we talk about food and calories, we're usually referring to macronutrients that contain carbon. Carbon provides energy for activity. The most popular macronutrients you'll hear about are protein, carbohydrate, fat, and alcohol. 

Alcohol is also a nutrient but, it interferes with growth, repair and maintenance in the body. While alcohol follows some different rules than carbohydrates, proteins and fats, we will discuss it here as it is a factor in energy balance.

So How Do I Figure out Calories?

Energy is typically expressed in kcalories or kilocalories. To make it easier this is often shortened into "calories". The energy is released from the food to be used by the body.

Different macronutrients contain different amounts of energy per gram:

  • Carbohydrates: 4
  • Fats: 9
  • Protein: 4
  • Alcohol: 7

Once you know how many grams of each your food has, it's pretty simple from here. All you need to do is some multiplication and addition. Let's walk through an example of this.

A serving of oreos (34g or 3 cookies) contains 7 grams of fat, 25 grams of carbohydrate, and 1 gram of protein:

  • 7 grams of fat x 9 calories per gram= 63 calories
  • 25 grams of carbohydrates x 4 calories per gram= 100 calories
  • 1 gram of protein x 4 calories per gram= 4 calories

A serving of oreos is labeled as containing 160 calories. Wait, what gives? Two reasons for this actually.

Why didn't that come out to 167? Fiber and rounding.

One reason for our odd Oreo calorie math is fiber. Fiber is typically not included in this math because it's special! You actually can't digest it and use the energy it carries. This is where the term "net carbohydrates" comes from. Net carbohydrates are the amount of carbs left over that your body can use, after you subtract fiber.

That means if you eat a food that has 100 grams of carbohydrates but, 24 of them are from fiber, you can subtract those 24 grams.

There are several benefits of fiber that could be listed here but, will be saved for another time.

Another reason that our math does not come out perfectly is because FDA standards allow food labels to round down to zero if that amount is under 5 calories.

Now that you know a little more about how to read a nutrition label, you can figure out how many calories you're eating!

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