You need the full article -- the abstract at the very least -- to make any sense of a study. Press releases are written by PR flacks who dumb down the science to the point where it is meaningless, as in this case. What you need to make sense of an experiment are details and context, neither of which the PR release in question provide. This is the problem with PR -- it's not a discipline that's meant to help you grasp complexity; it's about coming away with a simple, carefully chosen message.
Even if you have a whole article you have to proceed with caution. Interesting science tends to be about open questions; cutting edge topics tend to produce a diversity of opinion and contradictory evidence. What you need to read if you want to go to the horse's mouth in science is to read some literature review papers, like this one, which summarize the current state of research and the open questions at the time of writing. In fact you should probably read a recent review paper before you try to make sense of any individual paper. Having skimmed the review paper, it looks like the experiment we're discussing is attempting to explain a long-known experimental effect in terms of gut biota, which is a hot research field right now.
If all you had to make dietary decisions was the press release, you'd probably think, "Well, I'd better cut down on fat and sugar in my diet." The problem I have with that is that "fat" is a vast category of chemicals with wildly different physiological effects. Avoiding all fat because of this study would be like avoiding all acids because of a study of aspirin poisoning -- acids including all proteins and most vitamins.
What makes more sense is to consider all the proposed mechanisms, namely: chronic oxidative stress, inflammation, insulin resistance, and now disturbed gut flora. It's feasible to devise a lifestyle and diet which reduces *all* these things, which in turn would also improve our chances against other things like diabetes, autoimmune diseases, and cardiovascular disease. But so far as I know nobody's really put all that together yet. Science deals mainly in diseases, leaving health to the quacks.