Principle #1: Weight loss and weight gain come down to one key equation.
Everyone knows this one, though not everyone believes it. It’s the energy balance equation, also known as calories in, calories out (or CICO for short), and it looks like this:
[Energy in] – [Energy out] = Changes in body stores
In other words:
When you take in more energy (or calories) than you burn, you gain weight.
When you take in less energy than you burn, you lose weight.
When you take in the same energy as you burn, you maintain.
So you might be wondering: How do we know this with absolute certainty whereas “wine is bad/good for you” is still up for debate?
First, like gravity, this principle is easy to test. With gravity, you can continually release a heavy object. No matter how many times you try it, the object falls.
It’s the same with energy balance. If you reduce “energy in” and increase “energy out,” you always get the same result: Bodyweight goes down.
Second, the energy balance equation comes from the first law of thermodynamics:
Energy can neither be created or destroyed, only transferred from one state to another.
Humans can’t create energy from nothing. We convert it from food. And any excess energy we take in doesn’t magically vanish: Your body either increases “energy out” (often by turning up the metabolism) or stores the excess.
Scientific laws are as close to facts as we can get. Can they be updated over time? Sure. In this case, however, the law has stood firm for well over a century.
Many complex factors influence “calories in” and “calories out.” Your brain, especially, can turn up or turn down metabolism, exerting a massive influence on “calories out.”
To better understand the universality of energy balance, let’s circle back to another law you may have studied in physics class: the law of gravity.
Like energy balance, it’s also represented by the equation F = ma (force equals mass times acceleration). The basic equation applies to every object, dropped from any height. But a lot of factors affect it—like air resistance—making it seem like it’s not true.
Similarly, with food and humans, the basic equation never changes. It’s true of all foods consumed in all situations.
But, lots of factors can affect different parts of the equation.
What does this mean for you?
If someone wants to gain or lose body mass, they’ll want to consider overall energy balance and how to shift it in their favor. Here are a few ways to do just that.
To reduce calories in and increase calories out:
See references in principle 5