OK, maybe no one intends to lie but this mantra of ‘calores in, plus or minus, calories out= what you gain or lose’ is so often repeated and with such vehemence and condescension it may as well be a lie. In any case it is not true. Let me count the ways.
I think where the basic mistake is made is in asserting, don’t you love tautologies, ‘a calorie is a calorie so it has to be true.’ Well, oddly enough here is the first mistake. While it is true that a calorie is the amount of heat necessary to raise one gram of water one degree C from a certain base temperature and as that is the definition and tautologies are necessarily, though uninterestingly, true, that is not what they actually mean; and I don’t mean that a dietary calorie is 1,000 of the little calories of the definition.
First of all dietary calories are measured in a calorimiter, not in a human body and, face it we are all a little different, and we all burn fuel a little differently. Actually not so ‘little differently’ as the burn rate of any particular fuel for any particular activity can vary by up to 4(!) times from person to person. That is just the way it is get over it. You and I might weigh the same, walk the same speed, side by side and one burn more and one burn less. This matters because if you are focused on the caloric aspects of your diet and exercise you will miss the important variables that determine whether or not you will lose fat and gain muscle or lose muscle and gain fat or just get fat.
For those who would like to I will get into the very technical reasons why this is so…later. It invokes everything from bio-mechanics and vector analysis to biochemistry and genetics.
See also “Intensity”: GO