By Rich Weil, M.Ed. CDE
Founder and Director
Transformation Weight Control

This is an issue that people argue about all the time. I’m here to set the record, and the science, straight!

What Is a Calorie?
A calorie is the amount of energy needed to raise the temperature of one kilogram of water (one liter or 2.2 pounds) by one degree Celsius (33.8 degrees F). Keep this in mind as you read on.

How Do You Measure Calories in Food?
You use a device called a bomb calorimeter. It’s a big container with another container inside, you put food in it, ignite and combust the food, and measure the heat released. Here’s a step-by-step description of how it works. See the illustration below to follow along.
1. You take a measurement of the water temperature first as your baseline.
2. You put the food of interest into the sample dish inside the “bomb” container which is surrounded by the water.
3. You ignite and combust the food with an electric current via the ignition wires.
4. The heat released from the food combustion transfers to the water and heats it up.
5. The thermometer is very sensitive and measures the temperature of the water after it heats up.
6. Then the calculation is made to determine the caloric value, or energy, released from the food.

Now, let’s say you have four different foods, a cookie, cheese, slice of pie, and a vegetable, and you know with certainty from previous experiments that they all have the exact same number of calories. Let’s just say it’s 150 calories.

You put each one in the calorimeter separately, and once you have combusted all four foods, you will find that the calorimeter tells you they all still have the same number of calories, 150, which is to be expected. The number of the calories going in is exactly what the calorimeter shows.

Here’s the Catch
Say you have two food items that are exactly the same number of calories…

1. But… food #1 is highly processed, 80% raw sugar with no fiber.

2. And… food #2 is a high-fiber vegetable.

3. So… when you eat food #1 it is going to cause a large, rapid spike in your blood glucose (sugar, which is a form of glucose) because it gets absorbed by the body quicky. This doesn’t happen with food #2 because it has a high concentration of fiber which doesn’t break down and get absorbed as quickly as simple sugar.

4. Then… high levels of insulin will be secreted from the pancreas within 7 seconds of consumption to lower your blood sugar. Think of insulin like a key that unlocks cells, especially muscle cells, so that the glucose can exit the blood stream and enter the muscle cells for fuel. Just like a car burns gasoline for fuel, muscles burn glucose (and fat).

5. Then… sometime after this (30 minutes, an hour, it varies by how fast you metabolize the glucose), your blood sugar will crash as the insulin does its work, driving sugar out of the blood and into the muscles for fuel, and in to any other organ or tissue that needs it.

6. The brain’s principal source of fuel is glucose, about 20% of the body’s energy needs. If the brain goes low on glucose, then you will especially feel the crash which can cause confusion, disorientation, inability to focus or concentrate (some people call it brain fog), irritability, and loss of control and regulation over food intake.

7. And then… you get famished and disinhibited as your body craves calories to get back to normal levels. Disinhibition is the loss of control in your ability to inhibit or regulate your food intake, and can increase impulsivity.

8. And… then you eat more calories than you need or planned on.

9. And… if consumption of simple, raw sugar, happens on a regular basis, then the same thing will happen every time, and the extra calories are going to cause you to gain weight.

10. However… with food #2, this happens much less because the fiber in the vegetable slows down absorption and has the effect of regulating how much and how quickly the body absorbs the sugar, and of course, a fresh vegetable simply has less sugar than just a bunch of raw sugar.

So, it’s not that calories make a difference, it’s still the same number measured in the calorimeter, it’s just how the calories are processed, and then all the excess food consumption raw sugar will cause.

But Wait, There’s More, Much More – Ultra-Processed Food!
First, read our very own registered dietitian Molly Wangsgaard’s blog on ultra-processed food. And know that not only are ultra-processed foods hazardous to our health, but research shows that people can get addicted to it!

Still More – Digestibility!
You must consider that digestibility of foods varies for different people, which affects calorie storage. Some food you might absorb better than others and store the calories, and some food, such as very high insoluble fiber becomes, well you know, becomes poop! So again, the same number of calories are consumed, but the composition of the food makes the food more or less absorbed and stored.

And Yes, There’s Still More – Diet Induced Thermogenesis!
Consider diet induced thermogenesis, sometimes called the thermic effect of food. What’s that?  It’s the increase in calories burned after you eat, determined by the number of calories it takes to digest, absorb, and metabolize food you’ve eaten. It just so happens that it also raises your metabolic rate. You should keep in mind that the terms “thermogenic” or “thermic” are used because when you metabolize calories, heat is produced, just like the heat generated in the bomb calorimeter that raises the temperature of the water in the calorimeter. I suppose, in some way, you could say that your body is one big bomb calorimeter!

Yes, Sorry, Even More – Macronutrients!
There are three macronutrients that we eat; protein, carbohydrate, and fat. And do you know which has the highest thermogenic, or thermic effect?  That is, which macronutrient causes the greatest production of heat, or put another way, which one requires the most calories to be digested, absorbed, and metabolized. A lot of people think it’s fat. But that’s not correct. Protein has the highest thermogenic or thermic effect. It’s partly why you get more full from eating protein.

Okay, Final One, Promise – The Thrifty Gene! 
Ever heard of the thrifty gene? Putting it as simply as possible, it’s the genetic predisposition to store as many calories as you can from fat. This is an “adaptive” mechanism for survival dating back 10,000 years to hunter-gatherers. When food was available for our ancient relatives, their body’s thrifty gene went to work soaking up and storing as much fat as possible for use later on when food was scarce. The problem for us modern hunter-gatherers here in the 21^st century is, of course, that there is an abundance of food for many people, and you could go so far as to say, and overabundance.  But guess what? The thrifty gene hasn’t turned off and so when we eat, some of us may store more fat than others. It could take thousands to tens of thousands of generations for DNA to change enough to modify the thrifty gene. So, we’re not close yet to turning off our thrifty gene.

The Bottom Line
I will summarize. Whether it’s ultra-processed food you’re consuming, simple raw sugar, high fiber vegetables, foods with a high or low thermogenic or thermic effect, easily digestible foods that get stored or foods we easily eliminate, or your thrifty gene is more or less active than someone else’s, no matter what, if the calorimeter tells you they all have the same number of calories, then they do. The calorimeter does not tell you how all these foods with the same number of calories are digested, absorbed, or metabolized. And that’s why a calorie is a calorie. Because the bomb calorimeter says so. How food is processed might make it appear that not all calories are equal, but them in the calorimeter, and they are the same, then they are, and in the calorimeter, they’re going to raise the water by the same temperature no matter what. And that’s the bottom line.

A bomb calorimeter study that’s going to raise your eyebrows! I promise! Read on.               
Back at the lab I used to work at I had a colleague named Russell Rising. He was a scientist who did a lot of research on all things metabolic. One of his experiments was to compare the number of calories in a food as posted on the restaurant’s menu, and then he put the food in the bomb calorimeter to see how accurate the restaurant’s claim was. The results are mostly not pretty.  

What I’ve done is show the number of calories posted by the restaurant, then  right underneath are the calories of the food that Russ found when he put the food in the calorimeter, and then I calculated the difference for you.

Here you go. The first four foods show that the bomb calorimeter proved that there were more calories in the food than what the restaurant posted. For instance, there are 30% more calories in a Big Mac than what the restaurant posted!

But the final two are good news, a Starbucks Frappucino has 6.6% fewer calories posted at the restaurant than in the calorimeter. The bomb calorimeter is precise and tells it only the way it is!Thanks to Dr. Russell Rising for doing this research. I told you it would raise your eyebrows!

© Richard Weil, M.Ed., CDE, 2024 All Rights Reserved