Body shaming, and "My Big Fat Fabulous Life"

[Athene]

Scientifically, that is exactly what weight loss is about.

No shit, Sherlock - here's your sign.

Psychologically and physiologically it's a damn sight harder than that.

You can say that again.

From an evolutionary standpoint, our brains and bodies still consider food as scarce/difficult to come by. The human brain is programmed to interpret even a modest weight loss as starvation, and subsequently responds to it as a threat to survival . The brain makes no distinction between true starvation and a reduced calorie eating plan; It will "defend" the body with ruthless efficiency by attempting to hold on to existing fat stores (significantly slowing metabolism) and attempt to recover/regain any fat that's been lost (witholding/decreasing the release of hormones that signify fullness) all the same. 

That alone is enough to make voluntary, permanent weight-loss extraordinarily difficult to achieve and a highly unlikely state to maintain. Human beings are literally fighting an onslaught of real neurological/chemical responses honed by millions of years of evolution, that are expressly designed for the task to fail ; not just general laziness or a lack of "willpower". 

Keep in mind, that's without other contributing factors such as genetic predisposition, excessive cortisol production/additional hormonal issues, disorder/disease, addictive behavior, etc. even being brought into the picture.

This is why the notion of weight loss as a simple matter of calories in/calories out is nonsense. It's clearly an assertion that's primarily derived from ignorance (and personal distaste, I suspect) as it blatantly fails to account for the human body being a complex biological machine. The protests of those who insist that they're "logically" arguing the matter are quite laughable, considering the fact that ACTUAL scientists say otherwise.