At some point, there’s just physics. Running a mile isn’t free, benching 100kg isn’t free. These things take work and we can calculate the minimum energy requirement that adaptation can’t escape. Our bodies do not adapt so far that exercise becomes pointless, it only shifts the balance a little (which might be enough to be demotivating for some people, but it’s still relatively minor.) I was under the impression that the total range of metabolic adaptivity for a given person might be on the order of 25%-30% maybe. That might be an over-estimate. I googled a little and found this paper mentioning adaptations of like 8%-15% for severe calorie restriction diets (depending on how RMR is measured).
It’s not that much in terms of calories. It is a lot of physical activity for a modern human in a developed nation.
The real kicker is that an unchecked diet will offset virtually any amount of exercise. An unchecked diet means people will feel hungrier after exercise and thus eat more. It takes a lot of exercise to reach the point that it manages to outrun appetite and bad eating habits. There are a lot of fat people who work physically demanding jobs.
This in particular feels really hand wavy: “After weeks of training, they barely burned more energy per day when they were running 40 kilometers per week than before they started to train.”
What does “barely” mean? 40km/week isn’t that much in terms of calorie burn. The 100 calories/mile rule of thumb says this would imply ~350 calories/day. And this article says a woman would have a daily calorie expenditure of 2400 already (seems high, though). So this is only 15%. But anyway, this drops after adaptation seemingly, so does “barely more” mean 50 calories/day? Or does it mean 300? Because those are very different. And to where is the difference attributable? Because someone going from sedentary to trained runner is going to get a lot more efficient at running. “Less energy on inflammation” is really hard to swallow as the primary source of adaptation, especially when this is presented as conjecture.