What does a calorie measure?
ANSWER: If you guessed that a calorie measures energy, you would be correct; but what does that mean?
Slight history lesson: back in the 19th century, a chemist named Wilbur Atwater burned food that was sealed in a chamber submerged in a vat of water. As the food burned, the temperature of the water increased and Atwater measured the temperature change in calories!
One calorie (or kilocalorie) is the amount of heat that will raise the temp of one kilogram of water 1 degree C at sea level. That's a mouthful, right?
Think about it this way: you're trying to boil water on your gas stove top. If the flames are too small, there won't be enough heat and your water won't boil. At what point are the flames hot enough to get the water boiling?
That's the VERY GENERAL idea behind a calorie. It's exactly how much heat is needed to make the water increase in temperature 1 degree C.
What it's used for in the food world is to give an idea of how much ENERGY that food item will give to the consumer when "burned" up by the body. More calories = more potential energy.
Not everything is accounted for when counting calories, though. Only fat, carbohydrates, protein and alcohol are considered for a calorie total as those are the nutrients that give energy. All those studies that Atwater did on food contributes to our average calorie per gram count for each of these 4 nutrients. In other words, we don't burn food anymore - we use the averages found from Atwater's studies.
The U.S. uses the following guidelines: 1 gram of...
(*Fiber is not consider a carbohydrate readily absorbed by the body, so it's usually subtracted from the total gram count before adding up the calories - other times it is accounted for as 1 gram of fiber = 1.5 calories.)
However, not all energy is created equal. Suppose you have a choice between an 87 calorie orange and a 110 calorie pudding cup. While the pudding cup has more potential energy (higher calories) equated with it, it has ZERO nutritional value. It's mainly sugar and fat, which is why it's called an 'empty calorie' food choice. There is little to no benefit besides something to give the body a little boost for a short period of time.
Let's take my 20 fl oz butterscotch latte I had this afternoon and look at it's caloric breakdown.
45.6 g of fat * 9 = 410.4 calories from fat
64.5 g of carbs * 4 = 258 calories from carbohydrates
12.5 g of protein * 4 = 50 calories from protein
GRAND CALORIC TOTAL: 718.4
Yikes. I can guarantee you there was nothing healthy about this besides the joy it gave my taste buds. Did I get an energy boost? Possibly. That could also be the caffeine...
So make wise choices in your calorie consumption. Will you eat nutrient filled calories or empty calories? I am sure you know what will happen if you pick the latter option too often.