There are countless reasons why people fail to lose weight, but oftentimes it’s just due to a lack of understanding the scientifically proven principles behind it. If you don’t know what causes weight loss you will never achieve your fitness goals no matter how clean you eat or how perfectly you time your meals.

 

So, what actually causes weight loss?

 

You see, the most important variable here will always be a calorie deficit. This has been proven in hundreds of studies and can be considered a scientific fact for lack of a better term. No diet in the world will make you lose weight unless it also includes a calorie deficit.

 

But what exactly is a calorie deficit anyway?

 

From a scientific standpoint, whether you gain weight or lose weight is determined by the first law of thermodynamics which says that energy cannot be created or destroyed, it can only be transformed from one type to another.

 

When applied to dieting the first law of thermodynamics states that your body weight is dependent only on the difference between the number of calories that you consume versus the number of calories that you burn, which is known as your caloric balance.

 

Before we go into the different forms of calories balances, let’s first talk about what a calorie actually is. A (kilo)calorie is the amount of energy needed to raise the temperature of 1 liter of water by 1 degree Celsius. Therefore, a calorie is a form of energy measurement. When you eat food, you are consuming the energy that is stored in the food.

 

Your body then uses this energy to produce movement and keep your organism alive. Alternatively if not all energy is used right away it can also be stored for later use. Some energy can be in the muscles and liver as glycogen, but these stores fill up pretty quickly so your body will then stored any additional calories in the form of body fat.

 

 

There are 3 different states of calorie balance, and you can only be in ONE state at any time.

 

The first is a negative calorie balance. This occurs when someone burns MORE calories than he or she consumes. Here, your body needs more calories to produce energy for your daily functions than it gets for your food. That means it makes up the difference by burning stored energy, meaning you will lose weight.

 

Because the necessary energy will come from the breakdown of body tissues, a negative calorie balance ALWAYS results in weight loss. This can sometimes be masked by changes in water retention but if we exclude this factor there have been ZERO exceptions in medical history so far discovered.

 

The second state is a neutral calorie balance. Here, a person’s intake of calories is the same as his expenditure on activities and body processes. This means all the calories you consume will be used for some form of body process and your weight will remain stable.

 

Now, of course, calorie intakes and activities on any given day are not going to be 100% the same but over the course of weeks and months, a neutral calorie balance is quite possible. If you weight hasn’t changed over the last few months your calorie balance is almost always neutral.

 

The third and last state is a positive calorie balance. Here, more energy is consumed through food than is being burned to produce body processes or movement. The extra calories are stored as either glycogen in the muscle and liver or as fat.

 

As you can see from these three possible calorie balances only one will lead to weight loss, which is a negative calorie balance. How large this deficit is, also determines how much weight you can lose over a certain period of time. Obviously, the large the deficit the more weight you lose, but that doesn’t mean you should stop eating altogether to create the largest possible deficit. Please don’t crash diet. I will explain what the optimal deficit looks like in a later post.

 

When we look at this fact we can come up with a very simple equation that you are probably already familiar with:

 

 

Your “calories in” are determined by your diet meaning how many calories you consume on any given day. Your “calories out” are determined by a number of factors, most notably your metabolism, age, genetics and exercise regimen, with the last being the only one you can make meaningful changes to.

 

For example, you could reach a calorie deficit by not exercising and relying on your metabolism to burn let’s say 2500 calories and only consuming 2000. Or you could increase the calorie out by exercising and burning 500 additional calories in your workouts, which go on top of your normal 2500 calories. This will create 3000 calories on your calorie outside and allows you to consume let’s say 2500 calories and still be in a deficit. In both cases, your total daily deficit would be around 500 calories.

 

But no matter which way you choose to do it, one absolute requirement ALWAYS stands. In order to lose weight, you MUST create a caloric deficit. Nothing else works.