You're letting the word "are" carry a lot of weight where "often" or "can be" might be more accurate.

They're correlated with obesity, which means that they're more likely to be present in obese patients. But they exist independent of it: not being present for all obese patients and sometimes being present for non-obese patients. And since they're measurable on their own, it's kind of a big deal to draw them out as obesity-associated factors more closely correlated with all-cause mortality than obesity as a whole.