This actually isn’t entirely true. You’re operating under the “energy in-energy out” theory of weight loss, but human regulation of body fat is more complicated than that.
Specifically, we store energy in adipose tissue in the form of body fat after a meal (think of it like storing data on disk) and then when we are low on energy we burn that fat (load that data “in-memory”). However, a lot regulates when we burn fat. Blood sugar and insulin levels signal to the body not to burn fat and those come directly from carbohydrates. Additionally, carbohydrates are the initial energy source that is turned to fat. So with no carbs all your body knows how to do is burn fat for energy, and no additional intake of carbs means that there is no excess energy to store as fat to begin with. So, actually, even with a 5000 calorie diet you might see some weight loss... because your body has literally nothing (no carbs) to store as fat.
However, keto and low carb diets do have the benefit of the fact that they are entirely sustainable (unless you’re really addicted to bread) so I agree in that way they are behavioral :P
Specifically, we store energy in adipose tissue in the form of body fat after a meal (think of it like storing data on disk) and then when we are low on energy we burn that fat (load that data “in-memory”). However, a lot regulates when we burn fat. Blood sugar and insulin levels signal to the body not to burn fat and those come directly from carbohydrates. Additionally, carbohydrates are the initial energy source that is turned to fat. So with no carbs all your body knows how to do is burn fat for energy, and no additional intake of carbs means that there is no excess energy to store as fat to begin with. So, actually, even with a 5000 calorie diet you might see some weight loss... because your body has literally nothing (no carbs) to store as fat.
However, keto and low carb diets do have the benefit of the fact that they are entirely sustainable (unless you’re really addicted to bread) so I agree in that way they are behavioral :P