Is there any research with respect to how font-weight affects readability?

Is there any research with respect to how font-weight affects readability?

Obviously, there is some relation there, but I'm struggling to make a decision based on any facts.

I created a jsFiddle that demonstrates my issue or you can view the screenshot below.

I personally prefer the title with font-weight:100; as it's more slick, modern etc., but I'm worried that others might not be able to read it very well when there are many of these wrappers on a page. Also, it seems to me, that the "content text" under the title is heavier and is taking the eye away from the title.