> Calories in calories out works.
What do you mean by "works" here?
Technically it is true... the same way as "atoms in, atoms out" is technically true. So why do people prefer saying "calories in, calories out" instead of "atoms in, atoms out"?
That's because "calories in, calories out" implies that there is an easy solution to being fat... you simply need to "out" more calories, while you "in" less calories, duh!
Which conveniently ignores all possible problems with trying to "in" less calories and "out" more of them. For example, that your metabolism can make you feel extremely tired, even pass out, if you don't "in" enough calories. Similarly, to "out" more calories you sometimes need more than sheer willpower; your muscles have to cooperate, and sometimes they will only if you "in" enough calories.