Well, not entirely, although I'm fairly sympathetic to this way of looking at things.
For balance you should be ideally looking at calories absorbed = calories burned.
Why use different words? Well, firstly we absorb calories differently for different food types - we certainly do not absorb the full 100% of all calories available in any food. So measuring 'calories in' becomes 'caloric intake * %absorbtion'. It'll actually be some sort of integral of this products for each foodtype that you consume.
And then there is the question of calories burned. If you really want to stay slim, the best way to do so is to burn more energy when at rest. Of course, the easiest way to achieve this is by training your body to burn energy by doing exercise. But it is important to note that the calories burned just to keep you alive generally exceed the amount you burn during exercise by a decent factor.
But all of this is really nit-picking. Your basic premise remains true, you just can't beat physics. Anyone that is depending on this sort of information to optimise their weight-loss program has missed the point. Your lifestyle should not be so close to making you gain weight that these factors play an important role.