Additionally, do you acknowledge that some drives are more irresistible than others? Can you hold your breath until you pass out?
Is it so hard to imagine these drives might differ from person to person? I fully acknowledge that, irrespective of your body's efficiency, if you could ignore your drive magically, you would lose weight with no problem, but that is far from a useful endpoint because the drive matters.
Ultimately it's still calories in vs out. But the out isn't just burning 500 calories running. It's what you burn doing your day to day too.
https://examine.com/faq/does-metabolism-vary-between-two-peo...
Metabolic rate does vary, and technically there could be large variance. However, statistically speaking it is unlikely the variance would apply to you. The majority of the population exists in a range of 200-300kcal from each other and do not possess hugely different metabolic rates.
Sure, if you're tracking your food intake closely, maintaining a significant deficit, and not losing weight, talk to a doctor about your thyroid. If you're putting in hours in the gym and eating a lot and not gaining any muscle, talk to your doctor about your testosterone level. But if you're looking to hormones and whatnot first, you're probably just deluding yourself.
If I had to choose between thermodynamics and medicine being wrong, and people not being able to accurately estimate how "much" they eat and how "little" they exercise, I'd bet all my money on the latter.
The simple reality is, people have vastly different appetites. I eat fast and am always hungry. I have two coworkers, one eats quite a bit less than me (often struggles to finish a standard portion), the other eats mich more but quite slowly.
3 different people, 3 vastly different eating habits. The reason people gain different amounts of weight most likely isn't in the differences between our bodies, but the differences between our minds.