The module of calories in, calories out (CICO) is based in the first law thermodynamics that dictates that energy cannot be created or destroyed. Translating that into calories and body energy, the calories you eat have to be either used or stored. And if you do not use them, the alternative will make you fat. To a certain extent this is true, albeit, an oversimplification.
- Not all calories are the same:
- Not all calories are treated the same way:
- Metabolically adaptation:
Your body will force certain areas to consume less energy, eventually matching the energy expenditure to the incoming energy. For example you can feel more cold.
It's probably worth mentioning that if you're on a low carb diet and your body can easily access your fat reserves, the increase in calories won't necessary translate in an increase in fat storage, unless these reserves are very low. Ketones promote white fat cells to behave like brown fat cells and these consume more energy even on stand-by. So the result is, more fat on a low carb, after being fat adapted, usually equals to increase in energy only.
- Insulin - the traffic cop:
Before the fanfare of the low fat brigade and the food industry trying to force feed you sugars, crisps and sandwiches every hour of the day, we used to go hours in between meal. And all this on top of having a more laborious job and commutes. The current advice only causes insulin to stay high constantly.
In other words, the reason most people get morbidly obese is due to metabolic syndrome, or insulin resistance, which is when cells stop answering to insulin. In simple terms, the constant and high consumption of sugars and starches, made even worse by low fat, have made them insulin resistant, in that the body needs to use more insulin to do the same job it used to do with a lot less. This cause the insulin to be present in the blood stream for longer, the fat reserves to be inaccessible and eventually fat stores to not even be able to take anymore fat. It's a vicious circle.
So, calories matter matter?
The important thing to take note is that your metabolic rate is affected by what you eat and when you eat, not just how much you eat.
Insulin and the amount of carbohydrates you eat play a role and so does the periods you don't eat, either fasting or simply in between meals.
Snacking will hinder your process and so will eating a restricted calorie diet. Exercise helps but not to the extent anyone will make you believe. Exercise will impact your metabolic rate by a small margin. On top of this each body is different. Your body is constantly trying to maintain homeostasis.
In sum, eat real foods, eat low carb, eat high healthy fat, eat when hungry and stop when full.