I know it is human nature to see a number and look at an equivalent number and think they are the same. This works in math, this doesn't always work with how we try and calculate calories. A calorie is the amount of energy it takes to raise 1g of H20 1 degree C. a Calorie (actually is a KCal) is what we refer to with food, is the amount of energy it takes to raise a Kg of H20 1 degree.

This is a unit that is put into the body and has NO BEARING on what happens after that. This isn't simple accounting or math, the body is a complex system that uses several other processes to function. The unit of a Cal does not tell you the whole story, it doesn't take into considerate the amount of activity that takes place to utilize that Cal. This is extremely hard to explain to people that want to just look at Cal as all the same. Remember, your body doesn't have some external power source that you plug into, therefore, everything that happens in the body requires energy (which burn calories). It is made of of so many parts (organs) and how it operates and how efficient it is depends on several different variables. A book can be written regarding this issue, but lets look at it in simple terms.

If someone is Hypoglycemic or diabetic and has very LOW blood sugar, the first thing you want to give them is Sugar (in the most readily available form, preferably some type of hard candy). This is because the sugar is so easily and quickly processed to the blood stream.

On the other hand, Proteins actually REQUIRE energy to break them down. This "energy" means that you "burn" Calories to store Calories (or process them in the form where you can use it for energy in your blood stream).

This is why it is hard to say "well, if I am 500 Cal deficit eating CHO vs PRO, won't I still lose weight"? Yep, your gonna lose weight regardless, BUT if your diet is all PRO you will lose it faster.

There is so much to write on this regarding you thyroid, the pancreas, insulin and several other systems and feedback loops that take place in the body that this whole topic is incredibly complicated and scientists are still learning to this day.

I guess the closest way to look at it is.....The EPA ranks a certain car at 50 MPG and another at 50 MPG. BUT those cars can get dramatically different gas mileage depending on how it is driven (fast or slow), how many people or the overall weight of the car, head wind, inclines, and in what way the car is measured to get that MPG and what power source is used (gas, vs diesel vs hybrid). So if you have a Prius that is rated at 50 MPG, if you have 5 people in the car, have a head wind and are driving 120 MPH, it will get MUCH worse gas mileage than some Turbo Diesel truck from Europe that is also rated at 50 MPG under the same circumstances.

I am sure someone here has a better analogy or example, but just know that Calories are different depending on the type