I'd like to go out on a limb here and disagree with the well established laws of thermo-dynamics, but more specifically why they do not apply to biological factors so far up the scale.
I have worked with dozens of people who were trying to lose weight. Most people can do this with calories in versus calories out, however, not 100% of people can do it this way. I have worked with people who have restricted calories and increased activity levels (no cheats or any other discrepancies) and haven't lost weight. It's not many, but a single exception leads us to question the premise.
It's not that these few people are circumventing the laws of physics, it's that there are biological safe guards in place - there to prevent sudden changes in environment or sudden food scarcity from harming us. For some, restricting calories and increasing activity will shock the body into starvation mode. If this happens, your body will conserve fat to survive. It will slow down or switch off other non-essential processes. People in this state will make fewer involuntary movements, they will make fewer voluntary movements, core temp may drop, sleep may go on for longer, inhibited cognitive function, 'feeling tired'.
Decreasing calories eaten and increasing overt activity is not always effective.
FYI, for those of my clients who historically can't lose weight via calorie restriction/counting, always manage to on paleo (and that's without counting calories, because calorie counting is BORING)