Re-posted from an old thread...
It's actually a pretty big (though kinda silly) problem, imho, that 99% of the people who go around talking about (and counting and recommending) calories actually have no idea what the word means. So, inspired by a very good and important question by a 30BaD member, I want to first clear up what a calorie is, then rant a bit about our general ignorance. 
But don't worry, there's a point to this rant and I'll lead up to an important conclusion.
So, all aboard the rant-wagon! 
What is a Calorie:
First thing to understand is that there's actually no such "thing" as a calorie. A carbohydrate is a "thing" (i.e. it's an organic compound), whereas a calorie is just a unit of measurement - it's a way of measuring energy. We could just as easily say that you need a certain amount of kilojoules, but calorie is the common unit used in (and adapted by) the food industry. More specifically, a calorie is “the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, at a pressure of 1 atm.” Yep, it's just a unit of measurement.
So, no one in the history of the world has ever eaten "a calorie"; they've eaten some substance that's in turn provided their body with a certain amount of usable energy - what provides the body with 'calories' (i.e with energy) are organic compounds that the body is able to digest and assimilate, and these come in three general groups: proteins, carbs and fats. These groups also yield vastly different results in our bodies, as the conversions into energy (calories) is quite different for each one. But we can go into that another day.
Rant time...
Now, most people literally think they're counting some "thing" that they're eating, as if some part of that burger is a 'calorie', and there's 400 of those things in there! ;P This leads to the general ignorance expressed in what people think they mean when they say that "one calorie doesn't equal another", which, when one understands what a calorie is, is revealed for the ridiculous statement that it is. Of course every calorie is the same, just as every kilogram is the same, every pound is the same, every kilojoule is the same and every inch or centimeter or meter or mile is the same... Duh! But... the source of fuel that produces the calories is not the same!
Burning wood provides energy, and that can be measured in calories. Petroleum is an organic compound, and its potential energy output can also be calculated in terms of calories ("Diesel fuel contains 9,249 calories per liter, while gasoline has 8,269") just as the potential energy of a banana or an apple can be calculated in calories... but don't sit down with a meal of wood and a nice, tall glass of petroleum! ;P
Our bodies are very specific, minutely calibrated 'machines', built to utilize a very specific fuel for its energy needs - it cannot just convert any old substance into energy! Just as we don't put gas in a diesel engine or jet-fuel in a car or stuff uranium in a lawnmower, so also we better be careful what kind of fuel we put in our bodies. And that's why 80/10/10 is so damn important!
Our bodies also have mechanisms to store fuel, just like our cars do. Your car has a gas tank, so you don't need to have a hose feeding in fuel as you drive. Our body takes in organic compounds, breaks them down and stores some resulting compounds as potential energy, and uses others as energy for various uses. So, the next time you see someone fat walking around, just think to yourself: wow, that guy's got a lot of potential energy!! 
The other laughable thing is when people talk about "burning calories" and calculate how many calories they burned. Hehe... think about it this way: would anyone ever say that they were burning heat? Of course not, you burn a fuel (say, wood) and the fuel produces heat (a form of energy) which is usually measured in thermal units, but could be measured in calories or joules. It's not the heat that burns, it's the fuel. And the type of fuel makes all the difference.
Now the point of this rant is this: we really need to help people change their focus. Right now, people think they're doing themselves a favor by "limiting their calories", but they only think this way because they don't understand what a calorie is... they think 'limiting their calories' equals 'not getting fat', but actually all it means is "limiting their energy"!! That's what so many people are doing! Limiting their energy, purposefully! We need to get them past that. There should be no argument about energy: more energy = good. That should be obvious. And once we agree that more energy is good, then we can really discuss what fuel we ought to use to supply that energy. It's not the calories (the energy) that we ought to blame for our obesity epidemic; it's the FUEL!! Hell, it's energy that's gonna get us out of the obesity epidemic! Obese people need a crap-tonne of energy to get up and move! Skinny bitches need a crap-tonne of energy to get back to health! We all need energy!
So... when we say you need 3000+ calories at an 80/10/10 ratio, and we deliberately don't set a maximum, what we're saying is that in order for your body and mind to function adequately you need a certain minimum amount of energy, and the optimal source of energy for your body comes in the form of carbohydrates - that's the kind of 'machine' our body is; a carb-burnin' dynamo! We're also saying that the sky's the limit in terms of how much energy you wish to have! Fuel up to thrive is our saying around here!
Just ask yourself: how much energy do I want today!? Do I want to impose a cap on that? Do I want to say: "no, no, no, you can only have 2000 units of energy today, and no more"? Hell no! I want energy baby! I want to bubble with it! I want to radiate it! Let Nature impose her own limits on how much energy I can produce with this body, but I sure as hell aint gonna limit myself!!
So let's help educate people and shift the focus. Let's aim for maximum energy! And let's understand the human body so we can know what the right fuel to burn is! When we can shift our focus and educate ourselves, then we can get past this whole clinically-insane idea that somehow limiting our energy is the road to a lean, healthy body. It's not! Changing the fuel is!!
Rant over. 
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