[bokonist]

Or how do you think that cross-country runners got so skinny?

My guess is that the causation is reversed. Skinny people find running more enjoyable. I used to enjoy running cross-country when I was younger. As I've gotten older, I've filled out. I'm not fat, but I'm no longer thin and scrawny. As a result, I find running much more straining. I can feel it pound away on my knees, and I tend to get shin splints pretty quickly. So now I no longer run. I enjoy exercise - biking, soccer, etc. - but pounding pavement for 3 miles a day is no longer enjoyable.

Exercise CAN make you thin; thus, the statement that it won't is incorrect.

The article does not claim exercise can't make you thin. It claims it won't make you thin. No matter how many calories you burn, your body will send you overwhelming urges to eat more, to compensate for the lost calories. These urges - known as hunger - are incredibly difficult to resist, and thus you will not get any thinner.