A calorie is a measurement of energy. Fat, protein, carbohydrates, and alcohol are all nutrient that the body uses as energy. Body fat is essentially excess energy that’s stored throughout the body for later use. Therefore the only way to lose fat is by either consuming less energy (calories), expending more energy, or preferably a combination of the two. When you workout you use energy at an accelerated rate, but this will not amount to fat loss if you continuously eat more energy than you used. You have to use more energy than you’re taking in, thereby forcing your body to use your stored fat reserves. This is referred to as a caloric deficit, a term you may have heard before.
It used to be thought that consuming fatty foods is what led to body fat, but as it turns out, the body will store any form of excess energy regardless whether it is a carb, protein, or fat. Alcohol is somewhat unique in the sense that we don’t store the excess, or else we’d be drunk 24/7. Instead when we consume alcohol the body uses that as our energy supply, thereby preventing us from using the stored fat making it easier to accumulate more. Think of it as when your wallet is always full you will never have to dip into your saving account for money.
Just like we all love the idea of having a big saving account, the body loves having a big fat storage. Keep in mind that an excess of food energy is a relatively new phenomenon in human history. For the majority of our history we had to endure long periods with little or no food due to drought, migration, and so on. So our body has evolved to being very efficient at storing extra energy from our feast to be used during times of famine enable to survive. The good thing now is that there are no more famines, but we are still feasting and storing extra energy as if there are. I suppose in a couple thousand years of unnecessary extra energy intake our body will evolve and not store as much fat, but until then we’re just going have to do so manually.
This is precisely why diets don’t work. Most diets focus on limiting one macro nutrient ( carb, protein, fat) and increasing the other. But as you know by now when it comes to weight loss it’s not the type of energy that matters, but the overall energy consumption. So if you go on a low carb diet but increase your protein intake you’re still consuming the same total amount of energy. It’s like squeezing one end of a balloon, all you did was shift the air around. Pay attention to your overall energy consumption and you will get closer to your fitness goals.