The number of calories are measured in a food using a bomb calorimeter can be different from how many calories of the digested food are available for use to the human body. Also, some foods require more energy to be broken down. Some foods can trigger secondary effects that change behavior which could alter metabolism.
Now, I think those secondary considerations have a small impact on overall calorie consumption. For just about any food, a calorie measured by a bomb calorimeter is probably just about a calorie available to move the body, maintain the body, or stored in fat for later.
I don't think that's really OP's point. The point isn't that 1 calorie for me = 1 calorie for you. We know for a fact that the digestive performance of people can vary greatly, and caloric use varies greatly also depending on person and activity level.
The high variance is really besides the point, which is that if you are gaining weight, you are consuming too much for your current situation. You can either work to expend more, or reduce your intake, both of which are perfectly reasonable options.
There is no objective measure for eating too much, but it's also trivially easy to find out if you're eating too much for you.
>You can either work to expend more, or reduce your intake, both of which are perfectly reasonable options.
Perhaps I should be more clear: Your body has mechanisms for defeating your ability to work to expend more (fatigue), and driving you to eat (cravings, hunger pangs). I'm not arguing with your basic premise: you must consume less then you expend. I'm arguing with your "calorie is a calorie" dogma. For insulin insensitive people (read: overweight people), 1 calorie of fat will satisfy you more (turning on the satiety mechanism) better then 1 calorie of sugar will.
Now, I think those secondary considerations have a small impact on overall calorie consumption. For just about any food, a calorie measured by a bomb calorimeter is probably just about a calorie available to move the body, maintain the body, or stored in fat for later.
The body is a tough thing to study objectively.