IF you seem to believe that calorie in = calories out is junk
Junk is not a very useful word for this discussion - which is the reason why it is typically only used as a strawman argument. But, yes, calorie in = calorie out doesn't help much , for the following reasons :
1. It is tautological. It doesn't add anything to the discussion that is not already well known. Like x = x. Very true, and very useless statement, getting zero marks in all the infamous algebra questions asking to find x.
2. Calorie out is highly variable, unknown, difficult to measure.
3. Calorie in is also somewhat difficult to measure. Hope nobody here is taking the calories printed on food boxes as a gospel truth, rather than as a general guideline. One takes variable amount of energy from the same food - a lot depends on fat in feces, gut flora, and the micro-organisms excreted, among other things. To say nothing of how certain foods affect calorie out, making bomb calorimeters even less helpful.
4. Most importantly - and hence saved for the last - thermodynamics doesn't care about health, quality of life or even life/death of the person. In other words, no one sane ever has the goal of losing weight at any cost - death, disease, extreme discomfort, inability to work etc. When people say they want to lose weight, indirectly they are saying that they want to lose weight without losing :
A. life
B. basic comfort in life, maybe they can take some discomfort
C. ability to keep a job
D. health. They might even be hoping to improve their health.
But before they can put their goal in so many words, some smartass says calorie in = calorie out, killing the discussion. BTW, getting amputated or even cremated is an even more sure shot way to lose weight, consistent with the laws of thermodynamics.