Basically: people, we are learning a lot about our gut microbes. We don't know all the answers yet, but we are beginning to learn that it's an additional digestive organ, not just "critters" who live in our gut.
How do I know? Well, I had gestational diabetes with my youngest son. I had to test my blood sugars 7-8 times a day. Now, I didn't drink a lot of soda while pregnant, but I did have some and I did check my blood sugar after every, single meal and snack and I learned very quickly what spiked my blood sugar and what didn't. Basically, ANY grain or sugar - no matter the fiber content spiked my sugar levels. Only things that didn't were apples (paired with peanut butter) and potatoes.
Then, 5 years ago when my thyroid was completely out of whack, I had high blood sugars and a high HbA1C (sugar count over a long period in my blood). I was drinking one large soda a day, or adding a bit of Splenda to an iced tea (half a packet in a tall glass of tea). Again, I tested my blood sugars with every meal while I waited for readings to become normalized and again I saw the same triggers and I was not triggered by artificial sweeteners. Also,within three months of eating low carb and getting my thyroid in order, my fasting blood sugars were within normal and my HbA1C was near normal. Within 6 months it was well within middle range of normal.
With that said, I am wanting to wean myself off of diet sodas. Just yesterday I bought a few different brands of sparkling waters. I used to drink these waters instead of sodas, but stopped for some reason. I'm going to try to get back to that. Might be awhile before I stop slightly sweetening my iced tea, but baby steps it is. My protein bar has sucrolose (Splenda). So, I do get it, but I could cut back, but at least I don't appear to have the same problems these people in the studies are showing. Unless, of course, without the diet sodas and other things I would have a super low HbA1C result instead of being middle of normal range.