Since calorie is a measure of energy, so what does it mean when, for example, alcohol, having “empty calories”? What kind of energy is being measured here?
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From the perspective of energy, a calorie is pretty much a calorie.
However when considering nutrition nothing could be further from the truth.
People often liken the body to an automobile, so let’s use that comparison. If calories are the gas that makes the car go, then nutrients are the stuff that the car is built out of. Engine, transmission, electrical, brakes, etc are all parts of the car with unique functions but are also all generally made up of the same stuff in different amounts and configurations. Steel, copper, aluminum, plastic, etc
The human body is similar, except the structures in our body are made up of some combination of carbohydrates, proteins, and fats. Those are the major building blocks. That our parts are actually constructed from, or our macronutrients. However there are all micronutrients that are vital to the actual performance of those organs, like potassium, sodium, magnesium, iodine, etc. In our car example you can think of this stuff as like, your brake fluid, your transmission fluid, engine oil -stuff that’s actually vitally important to the running of the car that you might not guess at first glance because the car only contains them in relatively small quantities.
Now here is where the metaphor starts to break down- unlike a car which is a machine that’s assembled once in the factory and then generally just goes on it way, the body is a biological machine and all of our parts slowly degrade over time and need constant upkeep and maintenance where the car really just requires regular but infrequent attention.
So for the body, the ‘gas’ we consume is not only the energy that lets us get through the day, it’s also the building blocks that we’re made of. Our body is constantly making new cells for our blood and organs because there’s no natural mechanism for us to simply be able to swap parts like you can for a car. Medicine allows for that, but it’s not what our bodies are designed for. So it becomes vital that when we’re fueling our bodies we’re fueling it not just with energy to run, but with the necessary building blocks for our never sleeping mechanic to work with.
All of this to say, when we refer to empty calories it’s referring to food that is providing energy and little or nothing else. Sugars and corn syrups are probably the biggest culprit in the modern American diet, providing essentially nothing useful for our repairs. People also refer to processed carbohydrate as empty calories and while there are almost always better choices that can be made over a slice of wonderbread for example, it’s not technically true, as highly processed bread does still contain some scant amount of protein content.
If you ever want an example of someone that fuels themselves with foods that are going to have some of your best micro and macronutrient content, pay attention to what body builders eat. They don’t have a lot of room for excess in their diet based on what they’re asking their bodies to do, so you’ll see a lot of brown rice, broccoli or leafy greens, and chicken. Their diets will tend towards higher protein content but are a great starting point for folks just looking to eat healthy.
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