I read the Lancet paper (it's free if you are registered as a guest).
You're splitting hairs.
Weight loss IS as simple as CI<CO. That's what makes you lose weight.
But yes, psychologically, the motivation to lose weight in the obese is complicated by adaptive thermogenesis, leptin, etc as the paper says, as well as the obesogenic environment.
And the leptin hypothesis is under heavy fire now, too.
I fear recycling an old thread, but there's probably a teminology/semantics mismatch happening when people use expressions like "just eat fewer calories than you expend" - the 'just' part leads to quibbling.
Obviously nothing is that simple. "to win at chess just put your opponent's king into checkmate." - yeah, technically true, but incomplete information. There's more to it, sure, but you can't win a chess game without putting your opponent's king into checkmate. (ETA: alright, there's a point system for stalemates, but let's not get bogged down in the analogy)
One thing I'd like to contribute to the thread is that the evidence seems to strongly suggest that exercise doesn't play an important role in weight loss. It's still very important for overall health and life quality goals - so I'm a strong advocate for exercise - but I think it needs to be removed from the list of 'weight loss' or 'weight management' strategies.
At least not without a shovelful of additional education. Just as a concrete example: 'refuelling,' 'recovery' &c. All the facilities I worked in had concessions, snack machines, or even staffed juice bars that sold calorie dense liquid post-workout 'sports' drinks whose energy content far exceeded the strength workout's benefits (including muscle repair and BMR bump). Thanks to marketing science, these are positioned in the time and location most likely to intercept thirst and low blood sugar, ripe for bingeing.
This is just as much about the obesogenic environment as a weakness of strength training per se, but the patron has to be educated about the risk of net caloric surplus from 'refuelling' mythology for there to be a ghost of a chance that they will stick with water.
This predictable 'fat gain follows increased - but still moderate - exercise' effect appears paradoxical, but has credible mechanical explanations in terms of immediate post-workout calorie bingeing and long-term disproportionately increased appetite. So many independent studies show this effect that its lack of distribution to the public can only be explained through sheer disbelief ("It doesn't seem intuitive, the studies must be wrong.") and perhaps some cognitive dissonance ("If this is true, than my years of efforts to fight childhood obesity by advocating increased physical activity in children have all been misguided and perhaps counterproductive." or "If this is true, then my career as a fitness instructor may be contributing to obesity rather than being part of the solution.")
