the research isn't very good. it found a bunch of correlations between food and metabolic syndrome, a large set of related conditionsn including (but not always) elevated fasting blood sugar. the correlations least likely to be due to chance are meat and diet soda (but not any specific sweetener). unfortunately, this isn't surprising: one part of the definition of metabolic syndrome is a big waist, and it seems reasonable to me that people who are/consider themselves to be fat might drink more diet soda than otherwise.

the study's got some problems with its statistics that make the conclusions suspect, but i'll spare you the details unless you're interested. :)