Unsurprisingly, the title is sensationalist and not representative of the study. The study compares energy expenditure across different economic groups i.e. western people sitting in offices versus hunter-gatherers in Africa, and found that difference in energy expenditure does not account for differences in obesity, so points to consumption as the likely reason. The sample dataset explicitly excluded 'athletes', so…
> anyone who has done extensive 'athletic' physical activity knows that if you don't up your calorie intake that you will lose weight. Anyone who has done extensive athletic physical activity knows that you will up your calorie intake unless you take explicit and intentional effort not to.
This is why exercise alone often doesn't cause you to lose weight, or at least not as much as you'd expect given the extra calories you're burning: you're probably eating more (or the same amount, but foods with higher calorie density) than you were before, even if you didn't consciously choose to do so.