Comment by wildmanx

> So let's look at safer, more normal behavior. Call it -300 calories per day: either cutting diet by a medium order of fries each day (and keeping exercise fixed) or doing 40 minutes of moderate exercise (and keeping diet fixed).

That's not how it works though, and the article we are discussing here is hinting at that. The mechanisms are very complex. Going for a run for 40 min that "burns" 300 calories versus not going on that run won't create a calorie deficit of 300 calories. Because "everything else equal" is never going to happen.

There could be tons of effects happening to offset this. Eating more? Eating subtly different things? Eating it in different ways that impact nutrient uptake? More efficient nutrient uptake even when eating the same things in the same way at the same time? Changing patterns of movement that now use less energy? Change in overall metabolism (body temperature, body movements, ...)? Less stress, saving energy? ...? This is a very complex topic and "calories in versus calories out" is just not cutting it. And that's what the article is about. It's an approximation, but a so coarse one that it's barely usable for anything.