What is a Calorie? How accurate is a Calorie in our body?

a) What is a “Calorie”?

A calorie is the amount of heat required to raise the temperature of 1 gram of water by 1 degree Celsius.

The “calorie” that is talked about in the human body is actually a Kilocalorie, or 1,000 Calories. The press, many articles, and many nutritionists routinely misuse the term “Calorie” for the “Kilocalorie” (or “KCal”). To be correct, I will use the terms Calorie for a true Calorie and KCal for the nutritional term (as it should be).

To make my case- common sense tells us that the temperature of a small glass of cold water does not rock our calorific world.  Take 100 ml of cold water, normally at about 8C. Our body temp is 37C. Our body has to produce enough heat to warm the temp of the water to body temp, namely 29C. So, 1 ml of cold water requires 29 calories from our body to equilibrate to body temp. Therefore, 100 ml requires 2,900 calories! If nutritional calories were truly calories, this small glass of cold water would be a miraculous “diet” because it just took 2.900 calories away from our body!!  But it actually is only 2,900/1,000= 2.9 KCal, commonly “mis” labeled as 2.9 “Calories.”  (Yeah, I know…)

b) How accurate is a “Calorie” measurement in our body?

A calorie, or KCal, is measured in a beaker, in a lab. The measurement is done in a “closed” system. The beaker does not produce its own heat, or move, or have any life of its own.

The number of KCal a gram of fat (or protein, or carbohydrate) produces has also been measured in a lab setting. Burn 100 grams of Fat. Measure heat produced. Divide by 100. Voila! about 9 KCal/Gram. So far, so good.

Let us assume that my beaker (named “Fussy”) has “life”. We put 100 grams of Triglyceride of Stearic Acid (fat commonly found in meat) in it.  Oops, Fussy didn’t like it. Fussy’s walls stretch out. Fussy produces heat (on its own, not from the fat!). Fussy wants to get rid of this fat. Fussy produces 200 grams of gas, primarily Co2. Then Fussy produces 150 grams of Fluids. Then Fussy opens the bottom hatch and blows out all of the Triglyceride of Stearic Acid. Fussy uses 100 grams of gas and 50 grams of Fluids to do this. Fussy is upset and hot. Fussy just produced 120 Kcal of energy, gained 200 grams of weight (100 grams from gas and 100 grams from Fluids). None of the calories came from the Fat. KCal produced = 120. Kcal from Fat = 0. Weight Gain = 200 grams. Weight Gain due to Fat = 0.

Our bodies are far more complex than the exaggerated scenario I made up. The term KCal, or “calories”, and the number of Kcal associated with food, are all measured in ideal, “closed” systems- in a lab. It is a standardized way to measure and it is the proper way to measure.

The problem is in treating our human body like a “closed”, lab like system. It is not. The lab measured information has to be used “in context” to our very complex bodies.